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Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001/*
2 * Generic ring buffer
3 *
4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
5 */
6#include <linux/ring_buffer.h>
Ingo Molnar14131f22009-02-26 18:47:11 +01007#include <linux/trace_clock.h>
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04008#include <linux/spinlock.h>
9#include <linux/debugfs.h>
10#include <linux/uaccess.h>
Steven Rostedta81bd802009-02-06 01:45:16 -050011#include <linux/hardirq.h>
Vegard Nossum1744a212009-02-28 08:29:44 +010012#include <linux/kmemcheck.h>
Steven Rostedt7a8e76a2008-09-29 23:02:38 -040013#include <linux/module.h>
14#include <linux/percpu.h>
15#include <linux/mutex.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090016#include <linux/slab.h>
Steven Rostedt7a8e76a2008-09-29 23:02:38 -040017#include <linux/init.h>
18#include <linux/hash.h>
19#include <linux/list.h>
Steven Rostedt554f7862009-03-11 22:00:13 -040020#include <linux/cpu.h>
Steven Rostedt7a8e76a2008-09-29 23:02:38 -040021#include <linux/fs.h>
22
Christoph Lameter79615762010-01-05 15:34:50 +090023#include <asm/local.h>
Steven Rostedt182e9f52008-11-03 23:15:56 -050024#include "trace.h"
25
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -070026static void update_pages_handler(struct work_struct *work);
27
Steven Rostedt033601a2008-11-21 12:41:55 -050028/*
Steven Rostedtd1b182a2009-04-15 16:53:47 -040029 * The ring buffer header is special. We must manually up keep it.
30 */
31int ring_buffer_print_entry_header(struct trace_seq *s)
32{
33 int ret;
34
Lai Jiangshan334d4162009-04-24 11:27:05 +080035 ret = trace_seq_printf(s, "# compressed entry header\n");
36 ret = trace_seq_printf(s, "\ttype_len : 5 bits\n");
Steven Rostedtd1b182a2009-04-15 16:53:47 -040037 ret = trace_seq_printf(s, "\ttime_delta : 27 bits\n");
38 ret = trace_seq_printf(s, "\tarray : 32 bits\n");
39 ret = trace_seq_printf(s, "\n");
40 ret = trace_seq_printf(s, "\tpadding : type == %d\n",
41 RINGBUF_TYPE_PADDING);
42 ret = trace_seq_printf(s, "\ttime_extend : type == %d\n",
43 RINGBUF_TYPE_TIME_EXTEND);
Lai Jiangshan334d4162009-04-24 11:27:05 +080044 ret = trace_seq_printf(s, "\tdata max type_len == %d\n",
45 RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
Steven Rostedtd1b182a2009-04-15 16:53:47 -040046
47 return ret;
48}
49
50/*
Steven Rostedt5cc98542009-03-12 22:24:17 -040051 * The ring buffer is made up of a list of pages. A separate list of pages is
52 * allocated for each CPU. A writer may only write to a buffer that is
53 * associated with the CPU it is currently executing on. A reader may read
54 * from any per cpu buffer.
55 *
56 * The reader is special. For each per cpu buffer, the reader has its own
57 * reader page. When a reader has read the entire reader page, this reader
58 * page is swapped with another page in the ring buffer.
59 *
60 * Now, as long as the writer is off the reader page, the reader can do what
61 * ever it wants with that page. The writer will never write to that page
62 * again (as long as it is out of the ring buffer).
63 *
64 * Here's some silly ASCII art.
65 *
66 * +------+
67 * |reader| RING BUFFER
68 * |page |
69 * +------+ +---+ +---+ +---+
70 * | |-->| |-->| |
71 * +---+ +---+ +---+
72 * ^ |
73 * | |
74 * +---------------+
75 *
76 *
77 * +------+
78 * |reader| RING BUFFER
79 * |page |------------------v
80 * +------+ +---+ +---+ +---+
81 * | |-->| |-->| |
82 * +---+ +---+ +---+
83 * ^ |
84 * | |
85 * +---------------+
86 *
87 *
88 * +------+
89 * |reader| RING BUFFER
90 * |page |------------------v
91 * +------+ +---+ +---+ +---+
92 * ^ | |-->| |-->| |
93 * | +---+ +---+ +---+
94 * | |
95 * | |
96 * +------------------------------+
97 *
98 *
99 * +------+
100 * |buffer| RING BUFFER
101 * |page |------------------v
102 * +------+ +---+ +---+ +---+
103 * ^ | | | |-->| |
104 * | New +---+ +---+ +---+
105 * | Reader------^ |
106 * | page |
107 * +------------------------------+
108 *
109 *
110 * After we make this swap, the reader can hand this page off to the splice
111 * code and be done with it. It can even allocate a new page if it needs to
112 * and swap that into the ring buffer.
113 *
114 * We will be using cmpxchg soon to make all this lockless.
115 *
116 */
117
118/*
Steven Rostedt033601a2008-11-21 12:41:55 -0500119 * A fast way to enable or disable all ring buffers is to
120 * call tracing_on or tracing_off. Turning off the ring buffers
121 * prevents all ring buffers from being recorded to.
122 * Turning this switch on, makes it OK to write to the
123 * ring buffer, if the ring buffer is enabled itself.
124 *
125 * There's three layers that must be on in order to write
126 * to the ring buffer.
127 *
128 * 1) This global flag must be set.
129 * 2) The ring buffer must be enabled for recording.
130 * 3) The per cpu buffer must be enabled for recording.
131 *
132 * In case of an anomaly, this global flag has a bit set that
133 * will permantly disable all ring buffers.
134 */
135
136/*
137 * Global flag to disable all recording to ring buffers
138 * This has two bits: ON, DISABLED
139 *
140 * ON DISABLED
141 * ---- ----------
142 * 0 0 : ring buffers are off
143 * 1 0 : ring buffers are on
144 * X 1 : ring buffers are permanently disabled
145 */
146
147enum {
148 RB_BUFFERS_ON_BIT = 0,
149 RB_BUFFERS_DISABLED_BIT = 1,
150};
151
152enum {
153 RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT,
154 RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT,
155};
156
Hannes Eder5e398412009-02-10 19:44:34 +0100157static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
Steven Rostedta3583242008-11-11 15:01:42 -0500158
Steven Rostedt499e5472012-02-22 15:50:28 -0500159/* Used for individual buffers (after the counter) */
160#define RB_BUFFER_OFF (1 << 20)
161
Steven Rostedt474d32b2009-03-03 19:51:40 -0500162#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
163
Steven Rostedta3583242008-11-11 15:01:42 -0500164/**
Steven Rostedt033601a2008-11-21 12:41:55 -0500165 * tracing_off_permanent - permanently disable ring buffers
166 *
167 * This function, once called, will disable all ring buffers
Wenji Huangc3706f02009-02-10 01:03:18 -0500168 * permanently.
Steven Rostedt033601a2008-11-21 12:41:55 -0500169 */
170void tracing_off_permanent(void)
171{
172 set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
Steven Rostedta3583242008-11-11 15:01:42 -0500173}
174
Steven Rostedte3d6bf02009-03-03 13:53:07 -0500175#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
Andrew Morton67d34722009-01-09 12:27:09 -0800176#define RB_ALIGNMENT 4U
Lai Jiangshan334d4162009-04-24 11:27:05 +0800177#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
Steven Rostedtc7b09302009-06-11 11:12:00 -0400178#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
Lai Jiangshan334d4162009-04-24 11:27:05 +0800179
Steven Rostedt22710482010-03-18 17:54:19 -0400180#if !defined(CONFIG_64BIT) || defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
181# define RB_FORCE_8BYTE_ALIGNMENT 0
182# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
183#else
184# define RB_FORCE_8BYTE_ALIGNMENT 1
185# define RB_ARCH_ALIGNMENT 8U
186#endif
187
Lai Jiangshan334d4162009-04-24 11:27:05 +0800188/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
189#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400190
191enum {
192 RB_LEN_TIME_EXTEND = 8,
193 RB_LEN_TIME_STAMP = 16,
194};
195
Steven Rostedt69d1b832010-10-07 18:18:05 -0400196#define skip_time_extend(event) \
197 ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
198
Tom Zanussi2d622712009-03-22 03:30:49 -0500199static inline int rb_null_event(struct ring_buffer_event *event)
200{
Steven Rostedta1863c22009-09-03 10:23:58 -0400201 return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
Tom Zanussi2d622712009-03-22 03:30:49 -0500202}
203
204static void rb_event_set_padding(struct ring_buffer_event *event)
205{
Steven Rostedta1863c22009-09-03 10:23:58 -0400206 /* padding has a NULL time_delta */
Lai Jiangshan334d4162009-04-24 11:27:05 +0800207 event->type_len = RINGBUF_TYPE_PADDING;
Tom Zanussi2d622712009-03-22 03:30:49 -0500208 event->time_delta = 0;
209}
210
Tom Zanussi2d622712009-03-22 03:30:49 -0500211static unsigned
212rb_event_data_length(struct ring_buffer_event *event)
213{
214 unsigned length;
215
Lai Jiangshan334d4162009-04-24 11:27:05 +0800216 if (event->type_len)
217 length = event->type_len * RB_ALIGNMENT;
Tom Zanussi2d622712009-03-22 03:30:49 -0500218 else
219 length = event->array[0];
220 return length + RB_EVNT_HDR_SIZE;
221}
222
Steven Rostedt69d1b832010-10-07 18:18:05 -0400223/*
224 * Return the length of the given event. Will return
225 * the length of the time extend if the event is a
226 * time extend.
227 */
228static inline unsigned
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400229rb_event_length(struct ring_buffer_event *event)
230{
Lai Jiangshan334d4162009-04-24 11:27:05 +0800231 switch (event->type_len) {
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400232 case RINGBUF_TYPE_PADDING:
Tom Zanussi2d622712009-03-22 03:30:49 -0500233 if (rb_null_event(event))
234 /* undefined */
235 return -1;
Lai Jiangshan334d4162009-04-24 11:27:05 +0800236 return event->array[0] + RB_EVNT_HDR_SIZE;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400237
238 case RINGBUF_TYPE_TIME_EXTEND:
239 return RB_LEN_TIME_EXTEND;
240
241 case RINGBUF_TYPE_TIME_STAMP:
242 return RB_LEN_TIME_STAMP;
243
244 case RINGBUF_TYPE_DATA:
Tom Zanussi2d622712009-03-22 03:30:49 -0500245 return rb_event_data_length(event);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400246 default:
247 BUG();
248 }
249 /* not hit */
250 return 0;
251}
252
Steven Rostedt69d1b832010-10-07 18:18:05 -0400253/*
254 * Return total length of time extend and data,
255 * or just the event length for all other events.
256 */
257static inline unsigned
258rb_event_ts_length(struct ring_buffer_event *event)
259{
260 unsigned len = 0;
261
262 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
263 /* time extends include the data event after it */
264 len = RB_LEN_TIME_EXTEND;
265 event = skip_time_extend(event);
266 }
267 return len + rb_event_length(event);
268}
269
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400270/**
271 * ring_buffer_event_length - return the length of the event
272 * @event: the event to get the length of
Steven Rostedt69d1b832010-10-07 18:18:05 -0400273 *
274 * Returns the size of the data load of a data event.
275 * If the event is something other than a data event, it
276 * returns the size of the event itself. With the exception
277 * of a TIME EXTEND, where it still returns the size of the
278 * data load of the data event after it.
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400279 */
280unsigned ring_buffer_event_length(struct ring_buffer_event *event)
281{
Steven Rostedt69d1b832010-10-07 18:18:05 -0400282 unsigned length;
283
284 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
285 event = skip_time_extend(event);
286
287 length = rb_event_length(event);
Lai Jiangshan334d4162009-04-24 11:27:05 +0800288 if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
Robert Richter465634a2009-01-07 15:32:11 +0100289 return length;
290 length -= RB_EVNT_HDR_SIZE;
291 if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
292 length -= sizeof(event->array[0]);
293 return length;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400294}
Robert Richterc4f50182008-12-11 16:49:22 +0100295EXPORT_SYMBOL_GPL(ring_buffer_event_length);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400296
297/* inline for ring buffer fast paths */
Andrew Morton34a148b2009-01-09 12:27:09 -0800298static void *
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400299rb_event_data(struct ring_buffer_event *event)
300{
Steven Rostedt69d1b832010-10-07 18:18:05 -0400301 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
302 event = skip_time_extend(event);
Lai Jiangshan334d4162009-04-24 11:27:05 +0800303 BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400304 /* If length is in len field, then array[0] has the data */
Lai Jiangshan334d4162009-04-24 11:27:05 +0800305 if (event->type_len)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400306 return (void *)&event->array[0];
307 /* Otherwise length is in array[0] and array[1] has the data */
308 return (void *)&event->array[1];
309}
310
311/**
312 * ring_buffer_event_data - return the data of the event
313 * @event: the event to get the data from
314 */
315void *ring_buffer_event_data(struct ring_buffer_event *event)
316{
317 return rb_event_data(event);
318}
Robert Richterc4f50182008-12-11 16:49:22 +0100319EXPORT_SYMBOL_GPL(ring_buffer_event_data);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400320
321#define for_each_buffer_cpu(buffer, cpu) \
Rusty Russell9e01c1b2009-01-01 10:12:22 +1030322 for_each_cpu(cpu, buffer->cpumask)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400323
324#define TS_SHIFT 27
325#define TS_MASK ((1ULL << TS_SHIFT) - 1)
326#define TS_DELTA_TEST (~TS_MASK)
327
Steven Rostedt66a8cb92010-03-31 13:21:56 -0400328/* Flag when events were overwritten */
329#define RB_MISSED_EVENTS (1 << 31)
Steven Rostedtff0ff842010-03-31 22:11:42 -0400330/* Missed count stored at end */
331#define RB_MISSED_STORED (1 << 30)
Steven Rostedt66a8cb92010-03-31 13:21:56 -0400332
Steven Rostedtabc9b562008-12-02 15:34:06 -0500333struct buffer_data_page {
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400334 u64 time_stamp; /* page time stamp */
Wenji Huangc3706f02009-02-10 01:03:18 -0500335 local_t commit; /* write committed index */
Steven Rostedtabc9b562008-12-02 15:34:06 -0500336 unsigned char data[]; /* data of buffer page */
337};
338
Steven Rostedt77ae3652009-03-27 11:00:29 -0400339/*
340 * Note, the buffer_page list must be first. The buffer pages
341 * are allocated in cache lines, which means that each buffer
342 * page will be at the beginning of a cache line, and thus
343 * the least significant bits will be zero. We use this to
344 * add flags in the list struct pointers, to make the ring buffer
345 * lockless.
346 */
Steven Rostedtabc9b562008-12-02 15:34:06 -0500347struct buffer_page {
Steven Rostedt778c55d2009-05-01 18:44:45 -0400348 struct list_head list; /* list of buffer pages */
Steven Rostedtabc9b562008-12-02 15:34:06 -0500349 local_t write; /* index for next write */
Steven Rostedt6f807ac2008-10-04 02:00:58 -0400350 unsigned read; /* index for next read */
Steven Rostedt778c55d2009-05-01 18:44:45 -0400351 local_t entries; /* entries on this page */
Steven Rostedtff0ff842010-03-31 22:11:42 -0400352 unsigned long real_end; /* real end of data */
Steven Rostedtabc9b562008-12-02 15:34:06 -0500353 struct buffer_data_page *page; /* Actual data page */
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400354};
355
Steven Rostedt77ae3652009-03-27 11:00:29 -0400356/*
357 * The buffer page counters, write and entries, must be reset
358 * atomically when crossing page boundaries. To synchronize this
359 * update, two counters are inserted into the number. One is
360 * the actual counter for the write position or count on the page.
361 *
362 * The other is a counter of updaters. Before an update happens
363 * the update partition of the counter is incremented. This will
364 * allow the updater to update the counter atomically.
365 *
366 * The counter is 20 bits, and the state data is 12.
367 */
368#define RB_WRITE_MASK 0xfffff
369#define RB_WRITE_INTCNT (1 << 20)
370
Steven Rostedt044fa782008-12-02 23:50:03 -0500371static void rb_init_page(struct buffer_data_page *bpage)
Steven Rostedtabc9b562008-12-02 15:34:06 -0500372{
Steven Rostedt044fa782008-12-02 23:50:03 -0500373 local_set(&bpage->commit, 0);
Steven Rostedtabc9b562008-12-02 15:34:06 -0500374}
375
Steven Rostedt474d32b2009-03-03 19:51:40 -0500376/**
377 * ring_buffer_page_len - the size of data on the page.
378 * @page: The page to read
379 *
380 * Returns the amount of data on the page, including buffer page header.
381 */
Steven Rostedtef7a4a12009-03-03 00:27:49 -0500382size_t ring_buffer_page_len(void *page)
383{
Steven Rostedt474d32b2009-03-03 19:51:40 -0500384 return local_read(&((struct buffer_data_page *)page)->commit)
385 + BUF_PAGE_HDR_SIZE;
Steven Rostedtef7a4a12009-03-03 00:27:49 -0500386}
387
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400388/*
Steven Rostedted568292008-09-29 23:02:40 -0400389 * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
390 * this issue out.
391 */
Andrew Morton34a148b2009-01-09 12:27:09 -0800392static void free_buffer_page(struct buffer_page *bpage)
Steven Rostedted568292008-09-29 23:02:40 -0400393{
Andrew Morton34a148b2009-01-09 12:27:09 -0800394 free_page((unsigned long)bpage->page);
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400395 kfree(bpage);
Steven Rostedted568292008-09-29 23:02:40 -0400396}
397
398/*
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400399 * We need to fit the time_stamp delta into 27 bits.
400 */
401static inline int test_time_stamp(u64 delta)
402{
403 if (delta & TS_DELTA_TEST)
404 return 1;
405 return 0;
406}
407
Steven Rostedt474d32b2009-03-03 19:51:40 -0500408#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400409
Steven Rostedtbe957c42009-05-11 14:42:53 -0400410/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
411#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
412
Steven Rostedtd1b182a2009-04-15 16:53:47 -0400413int ring_buffer_print_page_header(struct trace_seq *s)
414{
415 struct buffer_data_page field;
416 int ret;
417
418 ret = trace_seq_printf(s, "\tfield: u64 timestamp;\t"
Tom Zanussi26a50742009-10-06 01:09:50 -0500419 "offset:0;\tsize:%u;\tsigned:%u;\n",
420 (unsigned int)sizeof(field.time_stamp),
421 (unsigned int)is_signed_type(u64));
Steven Rostedtd1b182a2009-04-15 16:53:47 -0400422
423 ret = trace_seq_printf(s, "\tfield: local_t commit;\t"
Tom Zanussi26a50742009-10-06 01:09:50 -0500424 "offset:%u;\tsize:%u;\tsigned:%u;\n",
Steven Rostedtd1b182a2009-04-15 16:53:47 -0400425 (unsigned int)offsetof(typeof(field), commit),
Tom Zanussi26a50742009-10-06 01:09:50 -0500426 (unsigned int)sizeof(field.commit),
427 (unsigned int)is_signed_type(long));
Steven Rostedtd1b182a2009-04-15 16:53:47 -0400428
Steven Rostedt66a8cb92010-03-31 13:21:56 -0400429 ret = trace_seq_printf(s, "\tfield: int overwrite;\t"
430 "offset:%u;\tsize:%u;\tsigned:%u;\n",
431 (unsigned int)offsetof(typeof(field), commit),
432 1,
433 (unsigned int)is_signed_type(long));
434
Steven Rostedtd1b182a2009-04-15 16:53:47 -0400435 ret = trace_seq_printf(s, "\tfield: char data;\t"
Tom Zanussi26a50742009-10-06 01:09:50 -0500436 "offset:%u;\tsize:%u;\tsigned:%u;\n",
Steven Rostedtd1b182a2009-04-15 16:53:47 -0400437 (unsigned int)offsetof(typeof(field), data),
Tom Zanussi26a50742009-10-06 01:09:50 -0500438 (unsigned int)BUF_PAGE_SIZE,
439 (unsigned int)is_signed_type(char));
Steven Rostedtd1b182a2009-04-15 16:53:47 -0400440
441 return ret;
442}
443
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400444/*
445 * head_page == tail_page && head == tail then buffer is empty.
446 */
447struct ring_buffer_per_cpu {
448 int cpu;
Richard Kennedy985023d2010-03-25 11:27:36 +0000449 atomic_t record_disabled;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400450 struct ring_buffer *buffer;
Thomas Gleixner5389f6f2009-07-25 17:13:33 +0200451 raw_spinlock_t reader_lock; /* serialize readers */
Thomas Gleixner445c8952009-12-02 19:49:50 +0100452 arch_spinlock_t lock;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400453 struct lock_class_key lock_key;
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -0800454 unsigned int nr_pages;
Steven Rostedt3adc54f2009-03-30 15:32:01 -0400455 struct list_head *pages;
Steven Rostedt6f807ac2008-10-04 02:00:58 -0400456 struct buffer_page *head_page; /* read from head */
457 struct buffer_page *tail_page; /* write to tail */
Wenji Huangc3706f02009-02-10 01:03:18 -0500458 struct buffer_page *commit_page; /* committed pages */
Steven Rostedtd7690412008-10-01 00:29:53 -0400459 struct buffer_page *reader_page;
Steven Rostedt66a8cb92010-03-31 13:21:56 -0400460 unsigned long lost_events;
461 unsigned long last_overrun;
Vaibhav Nagarnaikc64e1482011-08-16 14:46:16 -0700462 local_t entries_bytes;
Steven Rostedt77ae3652009-03-27 11:00:29 -0400463 local_t commit_overrun;
464 local_t overrun;
Steven Rostedte4906ef2009-04-30 20:49:44 -0400465 local_t entries;
Steven Rostedtfa743952009-06-16 12:37:57 -0400466 local_t committing;
467 local_t commits;
Steven Rostedt77ae3652009-03-27 11:00:29 -0400468 unsigned long read;
Vaibhav Nagarnaikc64e1482011-08-16 14:46:16 -0700469 unsigned long read_bytes;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400470 u64 write_stamp;
471 u64 read_stamp;
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -0800472 /* ring buffer pages to update, > 0 to add, < 0 to remove */
473 int nr_pages_to_update;
474 struct list_head new_pages; /* new pages to add */
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -0700475 struct work_struct update_pages_work;
Vaibhav Nagarnaik05fdd702012-05-18 13:29:51 -0700476 struct completion update_done;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400477};
478
479struct ring_buffer {
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400480 unsigned flags;
481 int cpus;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400482 atomic_t record_disabled;
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -0700483 atomic_t resize_disabled;
Arnaldo Carvalho de Melo00f62f62009-02-09 17:04:06 -0200484 cpumask_var_t cpumask;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400485
Peter Zijlstra1f8a6a12009-06-08 18:18:39 +0200486 struct lock_class_key *reader_lock_key;
487
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400488 struct mutex mutex;
489
490 struct ring_buffer_per_cpu **buffers;
Steven Rostedt554f7862009-03-11 22:00:13 -0400491
Steven Rostedt59222ef2009-03-12 11:46:03 -0400492#ifdef CONFIG_HOTPLUG_CPU
Steven Rostedt554f7862009-03-11 22:00:13 -0400493 struct notifier_block cpu_notify;
494#endif
Steven Rostedt37886f62009-03-17 17:22:06 -0400495 u64 (*clock)(void);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400496};
497
498struct ring_buffer_iter {
499 struct ring_buffer_per_cpu *cpu_buffer;
500 unsigned long head;
501 struct buffer_page *head_page;
Steven Rostedt492a74f2010-01-25 15:17:47 -0500502 struct buffer_page *cache_reader_page;
503 unsigned long cache_read;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400504 u64 read_stamp;
505};
506
Steven Rostedtf536aaf2008-11-10 23:07:30 -0500507/* buffer may be either ring_buffer or ring_buffer_per_cpu */
Steven Rostedt077c5402009-09-03 19:53:46 -0400508#define RB_WARN_ON(b, cond) \
509 ({ \
510 int _____ret = unlikely(cond); \
511 if (_____ret) { \
512 if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
513 struct ring_buffer_per_cpu *__b = \
514 (void *)b; \
515 atomic_inc(&__b->buffer->record_disabled); \
516 } else \
517 atomic_inc(&b->record_disabled); \
518 WARN_ON(1); \
519 } \
520 _____ret; \
Steven Rostedt3e89c7b2008-11-11 15:28:41 -0500521 })
Steven Rostedtf536aaf2008-11-10 23:07:30 -0500522
Steven Rostedt37886f62009-03-17 17:22:06 -0400523/* Up this if you want to test the TIME_EXTENTS and normalization */
524#define DEBUG_SHIFT 0
525
Jiri Olsa6d3f1e12009-10-23 19:36:19 -0400526static inline u64 rb_time_stamp(struct ring_buffer *buffer)
Steven Rostedt88eb0122009-05-11 16:28:23 -0400527{
528 /* shift to debug/test normalization and TIME_EXTENTS */
529 return buffer->clock() << DEBUG_SHIFT;
530}
531
Steven Rostedt37886f62009-03-17 17:22:06 -0400532u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
533{
534 u64 time;
535
536 preempt_disable_notrace();
Jiri Olsa6d3f1e12009-10-23 19:36:19 -0400537 time = rb_time_stamp(buffer);
Steven Rostedt37886f62009-03-17 17:22:06 -0400538 preempt_enable_no_resched_notrace();
539
540 return time;
541}
542EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
543
544void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
545 int cpu, u64 *ts)
546{
547 /* Just stupid testing the normalize function and deltas */
548 *ts >>= DEBUG_SHIFT;
549}
550EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
551
Steven Rostedt77ae3652009-03-27 11:00:29 -0400552/*
553 * Making the ring buffer lockless makes things tricky.
554 * Although writes only happen on the CPU that they are on,
555 * and they only need to worry about interrupts. Reads can
556 * happen on any CPU.
557 *
558 * The reader page is always off the ring buffer, but when the
559 * reader finishes with a page, it needs to swap its page with
560 * a new one from the buffer. The reader needs to take from
561 * the head (writes go to the tail). But if a writer is in overwrite
562 * mode and wraps, it must push the head page forward.
563 *
564 * Here lies the problem.
565 *
566 * The reader must be careful to replace only the head page, and
567 * not another one. As described at the top of the file in the
568 * ASCII art, the reader sets its old page to point to the next
569 * page after head. It then sets the page after head to point to
570 * the old reader page. But if the writer moves the head page
571 * during this operation, the reader could end up with the tail.
572 *
573 * We use cmpxchg to help prevent this race. We also do something
574 * special with the page before head. We set the LSB to 1.
575 *
576 * When the writer must push the page forward, it will clear the
577 * bit that points to the head page, move the head, and then set
578 * the bit that points to the new head page.
579 *
580 * We also don't want an interrupt coming in and moving the head
581 * page on another writer. Thus we use the second LSB to catch
582 * that too. Thus:
583 *
584 * head->list->prev->next bit 1 bit 0
585 * ------- -------
586 * Normal page 0 0
587 * Points to head page 0 1
588 * New head page 1 0
589 *
590 * Note we can not trust the prev pointer of the head page, because:
591 *
592 * +----+ +-----+ +-----+
593 * | |------>| T |---X--->| N |
594 * | |<------| | | |
595 * +----+ +-----+ +-----+
596 * ^ ^ |
597 * | +-----+ | |
598 * +----------| R |----------+ |
599 * | |<-----------+
600 * +-----+
601 *
602 * Key: ---X--> HEAD flag set in pointer
603 * T Tail page
604 * R Reader page
605 * N Next page
606 *
607 * (see __rb_reserve_next() to see where this happens)
608 *
609 * What the above shows is that the reader just swapped out
610 * the reader page with a page in the buffer, but before it
611 * could make the new header point back to the new page added
612 * it was preempted by a writer. The writer moved forward onto
613 * the new page added by the reader and is about to move forward
614 * again.
615 *
616 * You can see, it is legitimate for the previous pointer of
617 * the head (or any page) not to point back to itself. But only
618 * temporarially.
619 */
620
621#define RB_PAGE_NORMAL 0UL
622#define RB_PAGE_HEAD 1UL
623#define RB_PAGE_UPDATE 2UL
624
625
626#define RB_FLAG_MASK 3UL
627
628/* PAGE_MOVED is not part of the mask */
629#define RB_PAGE_MOVED 4UL
630
631/*
632 * rb_list_head - remove any bit
633 */
634static struct list_head *rb_list_head(struct list_head *list)
635{
636 unsigned long val = (unsigned long)list;
637
638 return (struct list_head *)(val & ~RB_FLAG_MASK);
639}
640
641/*
Jiri Olsa6d3f1e12009-10-23 19:36:19 -0400642 * rb_is_head_page - test if the given page is the head page
Steven Rostedt77ae3652009-03-27 11:00:29 -0400643 *
644 * Because the reader may move the head_page pointer, we can
645 * not trust what the head page is (it may be pointing to
646 * the reader page). But if the next page is a header page,
647 * its flags will be non zero.
648 */
Jesper Juhl42b16b32011-01-17 00:09:38 +0100649static inline int
Steven Rostedt77ae3652009-03-27 11:00:29 -0400650rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
651 struct buffer_page *page, struct list_head *list)
652{
653 unsigned long val;
654
655 val = (unsigned long)list->next;
656
657 if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
658 return RB_PAGE_MOVED;
659
660 return val & RB_FLAG_MASK;
661}
662
663/*
664 * rb_is_reader_page
665 *
666 * The unique thing about the reader page, is that, if the
667 * writer is ever on it, the previous pointer never points
668 * back to the reader page.
669 */
670static int rb_is_reader_page(struct buffer_page *page)
671{
672 struct list_head *list = page->list.prev;
673
674 return rb_list_head(list->next) != &page->list;
675}
676
677/*
678 * rb_set_list_to_head - set a list_head to be pointing to head.
679 */
680static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
681 struct list_head *list)
682{
683 unsigned long *ptr;
684
685 ptr = (unsigned long *)&list->next;
686 *ptr |= RB_PAGE_HEAD;
687 *ptr &= ~RB_PAGE_UPDATE;
688}
689
690/*
691 * rb_head_page_activate - sets up head page
692 */
693static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
694{
695 struct buffer_page *head;
696
697 head = cpu_buffer->head_page;
698 if (!head)
699 return;
700
701 /*
702 * Set the previous list pointer to have the HEAD flag.
703 */
704 rb_set_list_to_head(cpu_buffer, head->list.prev);
705}
706
707static void rb_list_head_clear(struct list_head *list)
708{
709 unsigned long *ptr = (unsigned long *)&list->next;
710
711 *ptr &= ~RB_FLAG_MASK;
712}
713
714/*
715 * rb_head_page_dactivate - clears head page ptr (for free list)
716 */
717static void
718rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
719{
720 struct list_head *hd;
721
722 /* Go through the whole list and clear any pointers found. */
723 rb_list_head_clear(cpu_buffer->pages);
724
725 list_for_each(hd, cpu_buffer->pages)
726 rb_list_head_clear(hd);
727}
728
729static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
730 struct buffer_page *head,
731 struct buffer_page *prev,
732 int old_flag, int new_flag)
733{
734 struct list_head *list;
735 unsigned long val = (unsigned long)&head->list;
736 unsigned long ret;
737
738 list = &prev->list;
739
740 val &= ~RB_FLAG_MASK;
741
Steven Rostedt08a40812009-09-14 09:31:35 -0400742 ret = cmpxchg((unsigned long *)&list->next,
743 val | old_flag, val | new_flag);
Steven Rostedt77ae3652009-03-27 11:00:29 -0400744
745 /* check if the reader took the page */
746 if ((ret & ~RB_FLAG_MASK) != val)
747 return RB_PAGE_MOVED;
748
749 return ret & RB_FLAG_MASK;
750}
751
752static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
753 struct buffer_page *head,
754 struct buffer_page *prev,
755 int old_flag)
756{
757 return rb_head_page_set(cpu_buffer, head, prev,
758 old_flag, RB_PAGE_UPDATE);
759}
760
761static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
762 struct buffer_page *head,
763 struct buffer_page *prev,
764 int old_flag)
765{
766 return rb_head_page_set(cpu_buffer, head, prev,
767 old_flag, RB_PAGE_HEAD);
768}
769
770static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
771 struct buffer_page *head,
772 struct buffer_page *prev,
773 int old_flag)
774{
775 return rb_head_page_set(cpu_buffer, head, prev,
776 old_flag, RB_PAGE_NORMAL);
777}
778
779static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
780 struct buffer_page **bpage)
781{
782 struct list_head *p = rb_list_head((*bpage)->list.next);
783
784 *bpage = list_entry(p, struct buffer_page, list);
785}
786
787static struct buffer_page *
788rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
789{
790 struct buffer_page *head;
791 struct buffer_page *page;
792 struct list_head *list;
793 int i;
794
795 if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
796 return NULL;
797
798 /* sanity check */
799 list = cpu_buffer->pages;
800 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
801 return NULL;
802
803 page = head = cpu_buffer->head_page;
804 /*
805 * It is possible that the writer moves the header behind
806 * where we started, and we miss in one loop.
807 * A second loop should grab the header, but we'll do
808 * three loops just because I'm paranoid.
809 */
810 for (i = 0; i < 3; i++) {
811 do {
812 if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
813 cpu_buffer->head_page = page;
814 return page;
815 }
816 rb_inc_page(cpu_buffer, &page);
817 } while (page != head);
818 }
819
820 RB_WARN_ON(cpu_buffer, 1);
821
822 return NULL;
823}
824
825static int rb_head_page_replace(struct buffer_page *old,
826 struct buffer_page *new)
827{
828 unsigned long *ptr = (unsigned long *)&old->list.prev->next;
829 unsigned long val;
830 unsigned long ret;
831
832 val = *ptr & ~RB_FLAG_MASK;
833 val |= RB_PAGE_HEAD;
834
Steven Rostedt08a40812009-09-14 09:31:35 -0400835 ret = cmpxchg(ptr, val, (unsigned long)&new->list);
Steven Rostedt77ae3652009-03-27 11:00:29 -0400836
837 return ret == val;
838}
839
840/*
841 * rb_tail_page_update - move the tail page forward
842 *
843 * Returns 1 if moved tail page, 0 if someone else did.
844 */
845static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
846 struct buffer_page *tail_page,
847 struct buffer_page *next_page)
848{
849 struct buffer_page *old_tail;
850 unsigned long old_entries;
851 unsigned long old_write;
852 int ret = 0;
853
854 /*
855 * The tail page now needs to be moved forward.
856 *
857 * We need to reset the tail page, but without messing
858 * with possible erasing of data brought in by interrupts
859 * that have moved the tail page and are currently on it.
860 *
861 * We add a counter to the write field to denote this.
862 */
863 old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
864 old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
865
866 /*
867 * Just make sure we have seen our old_write and synchronize
868 * with any interrupts that come in.
869 */
870 barrier();
871
872 /*
873 * If the tail page is still the same as what we think
874 * it is, then it is up to us to update the tail
875 * pointer.
876 */
877 if (tail_page == cpu_buffer->tail_page) {
878 /* Zero the write counter */
879 unsigned long val = old_write & ~RB_WRITE_MASK;
880 unsigned long eval = old_entries & ~RB_WRITE_MASK;
881
882 /*
883 * This will only succeed if an interrupt did
884 * not come in and change it. In which case, we
885 * do not want to modify it.
Lai Jiangshanda706d82009-07-15 16:27:30 +0800886 *
887 * We add (void) to let the compiler know that we do not care
888 * about the return value of these functions. We use the
889 * cmpxchg to only update if an interrupt did not already
890 * do it for us. If the cmpxchg fails, we don't care.
Steven Rostedt77ae3652009-03-27 11:00:29 -0400891 */
Lai Jiangshanda706d82009-07-15 16:27:30 +0800892 (void)local_cmpxchg(&next_page->write, old_write, val);
893 (void)local_cmpxchg(&next_page->entries, old_entries, eval);
Steven Rostedt77ae3652009-03-27 11:00:29 -0400894
895 /*
896 * No need to worry about races with clearing out the commit.
897 * it only can increment when a commit takes place. But that
898 * only happens in the outer most nested commit.
899 */
900 local_set(&next_page->page->commit, 0);
901
902 old_tail = cmpxchg(&cpu_buffer->tail_page,
903 tail_page, next_page);
904
905 if (old_tail == tail_page)
906 ret = 1;
907 }
908
909 return ret;
910}
911
912static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
913 struct buffer_page *bpage)
914{
915 unsigned long val = (unsigned long)bpage;
916
917 if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
918 return 1;
919
920 return 0;
921}
922
923/**
924 * rb_check_list - make sure a pointer to a list has the last bits zero
925 */
926static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
927 struct list_head *list)
928{
929 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
930 return 1;
931 if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
932 return 1;
933 return 0;
934}
935
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400936/**
937 * check_pages - integrity check of buffer pages
938 * @cpu_buffer: CPU buffer with pages to test
939 *
Wenji Huangc3706f02009-02-10 01:03:18 -0500940 * As a safety measure we check to make sure the data pages have not
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400941 * been corrupted.
942 */
943static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
944{
Steven Rostedt3adc54f2009-03-30 15:32:01 -0400945 struct list_head *head = cpu_buffer->pages;
Steven Rostedt044fa782008-12-02 23:50:03 -0500946 struct buffer_page *bpage, *tmp;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400947
Steven Rostedt308f7ee2012-05-16 19:46:32 -0400948 /* Reset the head page if it exists */
949 if (cpu_buffer->head_page)
950 rb_set_head_page(cpu_buffer);
951
Steven Rostedt77ae3652009-03-27 11:00:29 -0400952 rb_head_page_deactivate(cpu_buffer);
953
Steven Rostedt3e89c7b2008-11-11 15:28:41 -0500954 if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
955 return -1;
956 if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
957 return -1;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400958
Steven Rostedt77ae3652009-03-27 11:00:29 -0400959 if (rb_check_list(cpu_buffer, head))
960 return -1;
961
Steven Rostedt044fa782008-12-02 23:50:03 -0500962 list_for_each_entry_safe(bpage, tmp, head, list) {
Steven Rostedt3e89c7b2008-11-11 15:28:41 -0500963 if (RB_WARN_ON(cpu_buffer,
Steven Rostedt044fa782008-12-02 23:50:03 -0500964 bpage->list.next->prev != &bpage->list))
Steven Rostedt3e89c7b2008-11-11 15:28:41 -0500965 return -1;
966 if (RB_WARN_ON(cpu_buffer,
Steven Rostedt044fa782008-12-02 23:50:03 -0500967 bpage->list.prev->next != &bpage->list))
Steven Rostedt3e89c7b2008-11-11 15:28:41 -0500968 return -1;
Steven Rostedt77ae3652009-03-27 11:00:29 -0400969 if (rb_check_list(cpu_buffer, &bpage->list))
970 return -1;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400971 }
972
Steven Rostedt77ae3652009-03-27 11:00:29 -0400973 rb_head_page_activate(cpu_buffer);
974
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400975 return 0;
976}
977
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -0800978static int __rb_allocate_pages(int nr_pages, struct list_head *pages, int cpu)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400979{
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -0800980 int i;
Steven Rostedt044fa782008-12-02 23:50:03 -0500981 struct buffer_page *bpage, *tmp;
Steven Rostedt3adc54f2009-03-30 15:32:01 -0400982
Steven Rostedt7a8e76a2008-09-29 23:02:38 -0400983 for (i = 0; i < nr_pages; i++) {
Vaibhav Nagarnaik7ea59062011-05-03 17:56:42 -0700984 struct page *page;
Vaibhav Nagarnaikd7ec4bf2011-06-07 17:01:42 -0700985 /*
986 * __GFP_NORETRY flag makes sure that the allocation fails
987 * gracefully without invoking oom-killer and the system is
988 * not destabilized.
989 */
Steven Rostedt044fa782008-12-02 23:50:03 -0500990 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
Vaibhav Nagarnaikd7ec4bf2011-06-07 17:01:42 -0700991 GFP_KERNEL | __GFP_NORETRY,
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -0800992 cpu_to_node(cpu));
Steven Rostedt044fa782008-12-02 23:50:03 -0500993 if (!bpage)
Steven Rostedte4c2ce82008-10-01 11:14:54 -0400994 goto free_pages;
Steven Rostedt77ae3652009-03-27 11:00:29 -0400995
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -0800996 list_add(&bpage->list, pages);
Steven Rostedt77ae3652009-03-27 11:00:29 -0400997
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -0800998 page = alloc_pages_node(cpu_to_node(cpu),
Vaibhav Nagarnaikd7ec4bf2011-06-07 17:01:42 -0700999 GFP_KERNEL | __GFP_NORETRY, 0);
Vaibhav Nagarnaik7ea59062011-05-03 17:56:42 -07001000 if (!page)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001001 goto free_pages;
Vaibhav Nagarnaik7ea59062011-05-03 17:56:42 -07001002 bpage->page = page_address(page);
Steven Rostedt044fa782008-12-02 23:50:03 -05001003 rb_init_page(bpage->page);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001004 }
1005
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001006 return 0;
1007
1008free_pages:
1009 list_for_each_entry_safe(bpage, tmp, pages, list) {
1010 list_del_init(&bpage->list);
1011 free_buffer_page(bpage);
1012 }
1013
1014 return -ENOMEM;
1015}
1016
1017static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
1018 unsigned nr_pages)
1019{
1020 LIST_HEAD(pages);
1021
1022 WARN_ON(!nr_pages);
1023
1024 if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu))
1025 return -ENOMEM;
1026
Steven Rostedt3adc54f2009-03-30 15:32:01 -04001027 /*
1028 * The ring buffer page list is a circular list that does not
1029 * start and end with a list head. All page list items point to
1030 * other pages.
1031 */
1032 cpu_buffer->pages = pages.next;
1033 list_del(&pages);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001034
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001035 cpu_buffer->nr_pages = nr_pages;
1036
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001037 rb_check_pages(cpu_buffer);
1038
1039 return 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001040}
1041
1042static struct ring_buffer_per_cpu *
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001043rb_allocate_cpu_buffer(struct ring_buffer *buffer, int nr_pages, int cpu)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001044{
1045 struct ring_buffer_per_cpu *cpu_buffer;
Steven Rostedt044fa782008-12-02 23:50:03 -05001046 struct buffer_page *bpage;
Vaibhav Nagarnaik7ea59062011-05-03 17:56:42 -07001047 struct page *page;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001048 int ret;
1049
1050 cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
1051 GFP_KERNEL, cpu_to_node(cpu));
1052 if (!cpu_buffer)
1053 return NULL;
1054
1055 cpu_buffer->cpu = cpu;
1056 cpu_buffer->buffer = buffer;
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02001057 raw_spin_lock_init(&cpu_buffer->reader_lock);
Peter Zijlstra1f8a6a12009-06-08 18:18:39 +02001058 lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
Thomas Gleixneredc35bd2009-12-03 12:38:57 +01001059 cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001060 INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
Vaibhav Nagarnaik05fdd702012-05-18 13:29:51 -07001061 init_completion(&cpu_buffer->update_done);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001062
Steven Rostedt044fa782008-12-02 23:50:03 -05001063 bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
Steven Rostedte4c2ce82008-10-01 11:14:54 -04001064 GFP_KERNEL, cpu_to_node(cpu));
Steven Rostedt044fa782008-12-02 23:50:03 -05001065 if (!bpage)
Steven Rostedte4c2ce82008-10-01 11:14:54 -04001066 goto fail_free_buffer;
1067
Steven Rostedt77ae3652009-03-27 11:00:29 -04001068 rb_check_bpage(cpu_buffer, bpage);
1069
Steven Rostedt044fa782008-12-02 23:50:03 -05001070 cpu_buffer->reader_page = bpage;
Vaibhav Nagarnaik7ea59062011-05-03 17:56:42 -07001071 page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0);
1072 if (!page)
Steven Rostedte4c2ce82008-10-01 11:14:54 -04001073 goto fail_free_reader;
Vaibhav Nagarnaik7ea59062011-05-03 17:56:42 -07001074 bpage->page = page_address(page);
Steven Rostedt044fa782008-12-02 23:50:03 -05001075 rb_init_page(bpage->page);
Steven Rostedte4c2ce82008-10-01 11:14:54 -04001076
Steven Rostedtd7690412008-10-01 00:29:53 -04001077 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
Vaibhav Nagarnaik44b99462012-06-22 11:50:05 -07001078 INIT_LIST_HEAD(&cpu_buffer->new_pages);
Steven Rostedtd7690412008-10-01 00:29:53 -04001079
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001080 ret = rb_allocate_pages(cpu_buffer, nr_pages);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001081 if (ret < 0)
Steven Rostedtd7690412008-10-01 00:29:53 -04001082 goto fail_free_reader;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001083
1084 cpu_buffer->head_page
Steven Rostedt3adc54f2009-03-30 15:32:01 -04001085 = list_entry(cpu_buffer->pages, struct buffer_page, list);
Steven Rostedtbf41a152008-10-04 02:00:59 -04001086 cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001087
Steven Rostedt77ae3652009-03-27 11:00:29 -04001088 rb_head_page_activate(cpu_buffer);
1089
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001090 return cpu_buffer;
1091
Steven Rostedtd7690412008-10-01 00:29:53 -04001092 fail_free_reader:
1093 free_buffer_page(cpu_buffer->reader_page);
1094
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001095 fail_free_buffer:
1096 kfree(cpu_buffer);
1097 return NULL;
1098}
1099
1100static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
1101{
Steven Rostedt3adc54f2009-03-30 15:32:01 -04001102 struct list_head *head = cpu_buffer->pages;
Steven Rostedt044fa782008-12-02 23:50:03 -05001103 struct buffer_page *bpage, *tmp;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001104
Steven Rostedtd7690412008-10-01 00:29:53 -04001105 free_buffer_page(cpu_buffer->reader_page);
1106
Steven Rostedt77ae3652009-03-27 11:00:29 -04001107 rb_head_page_deactivate(cpu_buffer);
1108
Steven Rostedt3adc54f2009-03-30 15:32:01 -04001109 if (head) {
1110 list_for_each_entry_safe(bpage, tmp, head, list) {
1111 list_del_init(&bpage->list);
1112 free_buffer_page(bpage);
1113 }
1114 bpage = list_entry(head, struct buffer_page, list);
Steven Rostedt044fa782008-12-02 23:50:03 -05001115 free_buffer_page(bpage);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001116 }
Steven Rostedt3adc54f2009-03-30 15:32:01 -04001117
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001118 kfree(cpu_buffer);
1119}
1120
Steven Rostedt59222ef2009-03-12 11:46:03 -04001121#ifdef CONFIG_HOTPLUG_CPU
Frederic Weisbecker09c9e842009-03-21 04:33:36 +01001122static int rb_cpu_notify(struct notifier_block *self,
1123 unsigned long action, void *hcpu);
Steven Rostedt554f7862009-03-11 22:00:13 -04001124#endif
1125
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001126/**
1127 * ring_buffer_alloc - allocate a new ring_buffer
Robert Richter68814b52008-11-24 12:24:12 +01001128 * @size: the size in bytes per cpu that is needed.
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001129 * @flags: attributes to set for the ring buffer.
1130 *
1131 * Currently the only flag that is available is the RB_FL_OVERWRITE
1132 * flag. This flag means that the buffer will overwrite old data
1133 * when the buffer wraps. If this flag is not set, the buffer will
1134 * drop data when the tail hits the head.
1135 */
Peter Zijlstra1f8a6a12009-06-08 18:18:39 +02001136struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
1137 struct lock_class_key *key)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001138{
1139 struct ring_buffer *buffer;
1140 int bsize;
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001141 int cpu, nr_pages;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001142
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001143 /* keep it in its own cache line */
1144 buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
1145 GFP_KERNEL);
1146 if (!buffer)
1147 return NULL;
1148
Rusty Russell9e01c1b2009-01-01 10:12:22 +10301149 if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
1150 goto fail_free_buffer;
1151
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001152 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001153 buffer->flags = flags;
Steven Rostedt37886f62009-03-17 17:22:06 -04001154 buffer->clock = trace_clock_local;
Peter Zijlstra1f8a6a12009-06-08 18:18:39 +02001155 buffer->reader_lock_key = key;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001156
1157 /* need at least two pages */
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001158 if (nr_pages < 2)
1159 nr_pages = 2;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001160
Frederic Weisbecker3bf832c2009-03-19 14:47:33 +01001161 /*
1162 * In case of non-hotplug cpu, if the ring-buffer is allocated
1163 * in early initcall, it will not be notified of secondary cpus.
1164 * In that off case, we need to allocate for all possible cpus.
1165 */
1166#ifdef CONFIG_HOTPLUG_CPU
Steven Rostedt554f7862009-03-11 22:00:13 -04001167 get_online_cpus();
1168 cpumask_copy(buffer->cpumask, cpu_online_mask);
Frederic Weisbecker3bf832c2009-03-19 14:47:33 +01001169#else
1170 cpumask_copy(buffer->cpumask, cpu_possible_mask);
1171#endif
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001172 buffer->cpus = nr_cpu_ids;
1173
1174 bsize = sizeof(void *) * nr_cpu_ids;
1175 buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
1176 GFP_KERNEL);
1177 if (!buffer->buffers)
Rusty Russell9e01c1b2009-01-01 10:12:22 +10301178 goto fail_free_cpumask;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001179
1180 for_each_buffer_cpu(buffer, cpu) {
1181 buffer->buffers[cpu] =
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001182 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001183 if (!buffer->buffers[cpu])
1184 goto fail_free_buffers;
1185 }
1186
Steven Rostedt59222ef2009-03-12 11:46:03 -04001187#ifdef CONFIG_HOTPLUG_CPU
Steven Rostedt554f7862009-03-11 22:00:13 -04001188 buffer->cpu_notify.notifier_call = rb_cpu_notify;
1189 buffer->cpu_notify.priority = 0;
1190 register_cpu_notifier(&buffer->cpu_notify);
1191#endif
1192
1193 put_online_cpus();
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001194 mutex_init(&buffer->mutex);
1195
1196 return buffer;
1197
1198 fail_free_buffers:
1199 for_each_buffer_cpu(buffer, cpu) {
1200 if (buffer->buffers[cpu])
1201 rb_free_cpu_buffer(buffer->buffers[cpu]);
1202 }
1203 kfree(buffer->buffers);
1204
Rusty Russell9e01c1b2009-01-01 10:12:22 +10301205 fail_free_cpumask:
1206 free_cpumask_var(buffer->cpumask);
Steven Rostedt554f7862009-03-11 22:00:13 -04001207 put_online_cpus();
Rusty Russell9e01c1b2009-01-01 10:12:22 +10301208
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001209 fail_free_buffer:
1210 kfree(buffer);
1211 return NULL;
1212}
Peter Zijlstra1f8a6a12009-06-08 18:18:39 +02001213EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001214
1215/**
1216 * ring_buffer_free - free a ring buffer.
1217 * @buffer: the buffer to free.
1218 */
1219void
1220ring_buffer_free(struct ring_buffer *buffer)
1221{
1222 int cpu;
1223
Steven Rostedt554f7862009-03-11 22:00:13 -04001224 get_online_cpus();
1225
Steven Rostedt59222ef2009-03-12 11:46:03 -04001226#ifdef CONFIG_HOTPLUG_CPU
Steven Rostedt554f7862009-03-11 22:00:13 -04001227 unregister_cpu_notifier(&buffer->cpu_notify);
1228#endif
1229
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001230 for_each_buffer_cpu(buffer, cpu)
1231 rb_free_cpu_buffer(buffer->buffers[cpu]);
1232
Steven Rostedt554f7862009-03-11 22:00:13 -04001233 put_online_cpus();
1234
Eric Dumazetbd3f0222009-08-07 12:49:29 +02001235 kfree(buffer->buffers);
Rusty Russell9e01c1b2009-01-01 10:12:22 +10301236 free_cpumask_var(buffer->cpumask);
1237
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001238 kfree(buffer);
1239}
Robert Richterc4f50182008-12-11 16:49:22 +01001240EXPORT_SYMBOL_GPL(ring_buffer_free);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001241
Steven Rostedt37886f62009-03-17 17:22:06 -04001242void ring_buffer_set_clock(struct ring_buffer *buffer,
1243 u64 (*clock)(void))
1244{
1245 buffer->clock = clock;
1246}
1247
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001248static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
1249
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001250static inline unsigned long rb_page_entries(struct buffer_page *bpage)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001251{
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001252 return local_read(&bpage->entries) & RB_WRITE_MASK;
1253}
1254
1255static inline unsigned long rb_page_write(struct buffer_page *bpage)
1256{
1257 return local_read(&bpage->write) & RB_WRITE_MASK;
1258}
1259
Vaibhav Nagarnaik5040b4b2012-05-03 18:59:51 -07001260static int
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001261rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned int nr_pages)
1262{
1263 struct list_head *tail_page, *to_remove, *next_page;
1264 struct buffer_page *to_remove_page, *tmp_iter_page;
1265 struct buffer_page *last_page, *first_page;
1266 unsigned int nr_removed;
1267 unsigned long head_bit;
1268 int page_entries;
1269
1270 head_bit = 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001271
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02001272 raw_spin_lock_irq(&cpu_buffer->reader_lock);
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001273 atomic_inc(&cpu_buffer->record_disabled);
1274 /*
1275 * We don't race with the readers since we have acquired the reader
1276 * lock. We also don't race with writers after disabling recording.
1277 * This makes it easy to figure out the first and the last page to be
1278 * removed from the list. We unlink all the pages in between including
1279 * the first and last pages. This is done in a busy loop so that we
1280 * lose the least number of traces.
1281 * The pages are freed after we restart recording and unlock readers.
1282 */
1283 tail_page = &cpu_buffer->tail_page->list;
Steven Rostedt77ae3652009-03-27 11:00:29 -04001284
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001285 /*
1286 * tail page might be on reader page, we remove the next page
1287 * from the ring buffer
1288 */
1289 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
1290 tail_page = rb_list_head(tail_page->next);
1291 to_remove = tail_page;
1292
1293 /* start of pages to remove */
1294 first_page = list_entry(rb_list_head(to_remove->next),
1295 struct buffer_page, list);
1296
1297 for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
1298 to_remove = rb_list_head(to_remove)->next;
1299 head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001300 }
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001301
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001302 next_page = rb_list_head(to_remove)->next;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001303
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001304 /*
1305 * Now we remove all pages between tail_page and next_page.
1306 * Make sure that we have head_bit value preserved for the
1307 * next page
1308 */
1309 tail_page->next = (struct list_head *)((unsigned long)next_page |
1310 head_bit);
1311 next_page = rb_list_head(next_page);
1312 next_page->prev = tail_page;
1313
1314 /* make sure pages points to a valid page in the ring buffer */
1315 cpu_buffer->pages = next_page;
1316
1317 /* update head page */
1318 if (head_bit)
1319 cpu_buffer->head_page = list_entry(next_page,
1320 struct buffer_page, list);
1321
1322 /*
1323 * change read pointer to make sure any read iterators reset
1324 * themselves
1325 */
1326 cpu_buffer->read = 0;
1327
1328 /* pages are removed, resume tracing and then free the pages */
1329 atomic_dec(&cpu_buffer->record_disabled);
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02001330 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001331
1332 RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
1333
1334 /* last buffer page to remove */
1335 last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
1336 list);
1337 tmp_iter_page = first_page;
1338
1339 do {
1340 to_remove_page = tmp_iter_page;
1341 rb_inc_page(cpu_buffer, &tmp_iter_page);
1342
1343 /* update the counters */
1344 page_entries = rb_page_entries(to_remove_page);
1345 if (page_entries) {
1346 /*
1347 * If something was added to this page, it was full
1348 * since it is not the tail page. So we deduct the
1349 * bytes consumed in ring buffer from here.
Vaibhav Nagarnaik48fdc722012-06-29 12:31:41 -07001350 * Increment overrun to account for the lost events.
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001351 */
Vaibhav Nagarnaik48fdc722012-06-29 12:31:41 -07001352 local_add(page_entries, &cpu_buffer->overrun);
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001353 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
1354 }
1355
1356 /*
1357 * We have already removed references to this list item, just
1358 * free up the buffer_page and its page
1359 */
1360 free_buffer_page(to_remove_page);
1361 nr_removed--;
1362
1363 } while (to_remove_page != last_page);
1364
1365 RB_WARN_ON(cpu_buffer, nr_removed);
Vaibhav Nagarnaik5040b4b2012-05-03 18:59:51 -07001366
1367 return nr_removed == 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001368}
1369
Vaibhav Nagarnaik5040b4b2012-05-03 18:59:51 -07001370static int
1371rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001372{
Vaibhav Nagarnaik5040b4b2012-05-03 18:59:51 -07001373 struct list_head *pages = &cpu_buffer->new_pages;
1374 int retries, success;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001375
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02001376 raw_spin_lock_irq(&cpu_buffer->reader_lock);
Vaibhav Nagarnaik5040b4b2012-05-03 18:59:51 -07001377 /*
1378 * We are holding the reader lock, so the reader page won't be swapped
1379 * in the ring buffer. Now we are racing with the writer trying to
1380 * move head page and the tail page.
1381 * We are going to adapt the reader page update process where:
1382 * 1. We first splice the start and end of list of new pages between
1383 * the head page and its previous page.
1384 * 2. We cmpxchg the prev_page->next to point from head page to the
1385 * start of new pages list.
1386 * 3. Finally, we update the head->prev to the end of new list.
1387 *
1388 * We will try this process 10 times, to make sure that we don't keep
1389 * spinning.
1390 */
1391 retries = 10;
1392 success = 0;
1393 while (retries--) {
1394 struct list_head *head_page, *prev_page, *r;
1395 struct list_head *last_page, *first_page;
1396 struct list_head *head_page_with_bit;
Steven Rostedt77ae3652009-03-27 11:00:29 -04001397
Vaibhav Nagarnaik5040b4b2012-05-03 18:59:51 -07001398 head_page = &rb_set_head_page(cpu_buffer)->list;
1399 prev_page = head_page->prev;
1400
1401 first_page = pages->next;
1402 last_page = pages->prev;
1403
1404 head_page_with_bit = (struct list_head *)
1405 ((unsigned long)head_page | RB_PAGE_HEAD);
1406
1407 last_page->next = head_page_with_bit;
1408 first_page->prev = prev_page;
1409
1410 r = cmpxchg(&prev_page->next, head_page_with_bit, first_page);
1411
1412 if (r == head_page_with_bit) {
1413 /*
1414 * yay, we replaced the page pointer to our new list,
1415 * now, we just have to update to head page's prev
1416 * pointer to point to end of list
1417 */
1418 head_page->prev = last_page;
1419 success = 1;
1420 break;
1421 }
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001422 }
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001423
Vaibhav Nagarnaik5040b4b2012-05-03 18:59:51 -07001424 if (success)
1425 INIT_LIST_HEAD(pages);
1426 /*
1427 * If we weren't successful in adding in new pages, warn and stop
1428 * tracing
1429 */
1430 RB_WARN_ON(cpu_buffer, !success);
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02001431 raw_spin_unlock_irq(&cpu_buffer->reader_lock);
Vaibhav Nagarnaik5040b4b2012-05-03 18:59:51 -07001432
1433 /* free pages if they weren't inserted */
1434 if (!success) {
1435 struct buffer_page *bpage, *tmp;
1436 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1437 list) {
1438 list_del_init(&bpage->list);
1439 free_buffer_page(bpage);
1440 }
1441 }
1442 return success;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001443}
1444
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001445static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001446{
Vaibhav Nagarnaik5040b4b2012-05-03 18:59:51 -07001447 int success;
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001448
Vaibhav Nagarnaik5040b4b2012-05-03 18:59:51 -07001449 if (cpu_buffer->nr_pages_to_update > 0)
1450 success = rb_insert_pages(cpu_buffer);
1451 else
1452 success = rb_remove_pages(cpu_buffer,
1453 -cpu_buffer->nr_pages_to_update);
1454
1455 if (success)
1456 cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001457}
1458
1459static void update_pages_handler(struct work_struct *work)
1460{
1461 struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
1462 struct ring_buffer_per_cpu, update_pages_work);
1463 rb_update_pages(cpu_buffer);
Vaibhav Nagarnaik05fdd702012-05-18 13:29:51 -07001464 complete(&cpu_buffer->update_done);
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001465}
1466
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001467/**
1468 * ring_buffer_resize - resize the ring buffer
1469 * @buffer: the buffer to resize.
1470 * @size: the new size.
1471 *
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001472 * Minimum size is 2 * BUF_PAGE_SIZE.
1473 *
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001474 * Returns 0 on success and < 0 on failure.
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001475 */
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001476int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
1477 int cpu_id)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001478{
1479 struct ring_buffer_per_cpu *cpu_buffer;
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001480 unsigned nr_pages;
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001481 int cpu, err = 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001482
Ingo Molnaree51a1d2008-11-13 14:58:31 +01001483 /*
1484 * Always succeed at resizing a non-existent buffer:
1485 */
1486 if (!buffer)
1487 return size;
1488
Steven Rostedt6a31e1f2012-05-23 15:35:17 -04001489 /* Make sure the requested buffer exists */
1490 if (cpu_id != RING_BUFFER_ALL_CPUS &&
1491 !cpumask_test_cpu(cpu_id, buffer->cpumask))
1492 return size;
1493
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001494 size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1495 size *= BUF_PAGE_SIZE;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001496
1497 /* we need a minimum of two pages */
1498 if (size < BUF_PAGE_SIZE * 2)
1499 size = BUF_PAGE_SIZE * 2;
1500
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001501 nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
1502
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001503 /*
1504 * Don't succeed if resizing is disabled, as a reader might be
1505 * manipulating the ring buffer and is expecting a sane state while
1506 * this is true.
1507 */
1508 if (atomic_read(&buffer->resize_disabled))
1509 return -EBUSY;
1510
1511 /* prevent another thread from changing buffer sizes */
1512 mutex_lock(&buffer->mutex);
1513
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001514 if (cpu_id == RING_BUFFER_ALL_CPUS) {
1515 /* calculate the pages to update */
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001516 for_each_buffer_cpu(buffer, cpu) {
1517 cpu_buffer = buffer->buffers[cpu];
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001518
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001519 cpu_buffer->nr_pages_to_update = nr_pages -
1520 cpu_buffer->nr_pages;
Vaibhav Nagarnaikd7ec4bf2011-06-07 17:01:42 -07001521 /*
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001522 * nothing more to do for removing pages or no update
Vaibhav Nagarnaikd7ec4bf2011-06-07 17:01:42 -07001523 */
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001524 if (cpu_buffer->nr_pages_to_update <= 0)
1525 continue;
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001526 /*
1527 * to add pages, make sure all new pages can be
1528 * allocated without receiving ENOMEM
1529 */
1530 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1531 if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update,
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001532 &cpu_buffer->new_pages, cpu)) {
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001533 /* not enough memory for new pages */
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001534 err = -ENOMEM;
1535 goto out_err;
1536 }
1537 }
1538
1539 get_online_cpus();
1540 /*
1541 * Fire off all the required work handlers
Vaibhav Nagarnaik05fdd702012-05-18 13:29:51 -07001542 * We can't schedule on offline CPUs, but it's not necessary
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001543 * since we can change their buffer sizes without any race.
1544 */
1545 for_each_buffer_cpu(buffer, cpu) {
1546 cpu_buffer = buffer->buffers[cpu];
Vaibhav Nagarnaik05fdd702012-05-18 13:29:51 -07001547 if (!cpu_buffer->nr_pages_to_update)
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001548 continue;
1549
Vaibhav Nagarnaik05fdd702012-05-18 13:29:51 -07001550 if (cpu_online(cpu))
1551 schedule_work_on(cpu,
1552 &cpu_buffer->update_pages_work);
1553 else
1554 rb_update_pages(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001555 }
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001556
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001557 /* wait for all the updates to complete */
1558 for_each_buffer_cpu(buffer, cpu) {
1559 cpu_buffer = buffer->buffers[cpu];
Vaibhav Nagarnaik05fdd702012-05-18 13:29:51 -07001560 if (!cpu_buffer->nr_pages_to_update)
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001561 continue;
1562
Vaibhav Nagarnaik05fdd702012-05-18 13:29:51 -07001563 if (cpu_online(cpu))
1564 wait_for_completion(&cpu_buffer->update_done);
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001565 cpu_buffer->nr_pages_to_update = 0;
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001566 }
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001567
1568 put_online_cpus();
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001569 } else {
Vaibhav Nagarnaik8e49f412012-10-10 16:40:27 -07001570 /* Make sure this CPU has been intitialized */
1571 if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
1572 goto out;
1573
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001574 cpu_buffer = buffer->buffers[cpu_id];
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001575
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001576 if (nr_pages == cpu_buffer->nr_pages)
1577 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001578
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001579 cpu_buffer->nr_pages_to_update = nr_pages -
1580 cpu_buffer->nr_pages;
1581
1582 INIT_LIST_HEAD(&cpu_buffer->new_pages);
1583 if (cpu_buffer->nr_pages_to_update > 0 &&
1584 __rb_allocate_pages(cpu_buffer->nr_pages_to_update,
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001585 &cpu_buffer->new_pages, cpu_id)) {
1586 err = -ENOMEM;
1587 goto out_err;
1588 }
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001589
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001590 get_online_cpus();
1591
1592 if (cpu_online(cpu_id)) {
1593 schedule_work_on(cpu_id,
1594 &cpu_buffer->update_pages_work);
Vaibhav Nagarnaik05fdd702012-05-18 13:29:51 -07001595 wait_for_completion(&cpu_buffer->update_done);
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001596 } else
1597 rb_update_pages(cpu_buffer);
1598
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001599 cpu_buffer->nr_pages_to_update = 0;
Vaibhav Nagarnaik05fdd702012-05-18 13:29:51 -07001600 put_online_cpus();
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001601 }
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001602
1603 out:
Steven Rostedt659f4512012-05-14 17:02:33 -04001604 /*
1605 * The ring buffer resize can happen with the ring buffer
1606 * enabled, so that the update disturbs the tracing as little
1607 * as possible. But if the buffer is disabled, we do not need
1608 * to worry about that, and we can take the time to verify
1609 * that the buffer is not corrupt.
1610 */
1611 if (atomic_read(&buffer->record_disabled)) {
1612 atomic_inc(&buffer->record_disabled);
1613 /*
1614 * Even though the buffer was disabled, we must make sure
1615 * that it is truly disabled before calling rb_check_pages.
1616 * There could have been a race between checking
1617 * record_disable and incrementing it.
1618 */
1619 synchronize_sched();
1620 for_each_buffer_cpu(buffer, cpu) {
1621 cpu_buffer = buffer->buffers[cpu];
1622 rb_check_pages(cpu_buffer);
1623 }
1624 atomic_dec(&buffer->record_disabled);
1625 }
1626
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001627 mutex_unlock(&buffer->mutex);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001628 return size;
1629
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001630 out_err:
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001631 for_each_buffer_cpu(buffer, cpu) {
1632 struct buffer_page *bpage, *tmp;
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001633
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001634 cpu_buffer = buffer->buffers[cpu];
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001635 cpu_buffer->nr_pages_to_update = 0;
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001636
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001637 if (list_empty(&cpu_buffer->new_pages))
1638 continue;
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001639
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001640 list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
1641 list) {
1642 list_del_init(&bpage->list);
1643 free_buffer_page(bpage);
1644 }
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001645 }
Vegard Nossum641d2f62008-11-18 19:22:13 +01001646 mutex_unlock(&buffer->mutex);
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07001647 return err;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001648}
Robert Richterc4f50182008-12-11 16:49:22 +01001649EXPORT_SYMBOL_GPL(ring_buffer_resize);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001650
David Sharp750912f2010-12-08 13:46:47 -08001651void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val)
1652{
1653 mutex_lock(&buffer->mutex);
1654 if (val)
1655 buffer->flags |= RB_FL_OVERWRITE;
1656 else
1657 buffer->flags &= ~RB_FL_OVERWRITE;
1658 mutex_unlock(&buffer->mutex);
1659}
1660EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
1661
Steven Rostedt8789a9e2008-12-02 15:34:07 -05001662static inline void *
Steven Rostedt044fa782008-12-02 23:50:03 -05001663__rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
Steven Rostedt8789a9e2008-12-02 15:34:07 -05001664{
Steven Rostedt044fa782008-12-02 23:50:03 -05001665 return bpage->data + index;
Steven Rostedt8789a9e2008-12-02 15:34:07 -05001666}
1667
Steven Rostedt044fa782008-12-02 23:50:03 -05001668static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001669{
Steven Rostedt044fa782008-12-02 23:50:03 -05001670 return bpage->page->data + index;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001671}
1672
1673static inline struct ring_buffer_event *
Steven Rostedtd7690412008-10-01 00:29:53 -04001674rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001675{
Steven Rostedt6f807ac2008-10-04 02:00:58 -04001676 return __rb_page_index(cpu_buffer->reader_page,
1677 cpu_buffer->reader_page->read);
1678}
1679
1680static inline struct ring_buffer_event *
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001681rb_iter_head_event(struct ring_buffer_iter *iter)
1682{
Steven Rostedt6f807ac2008-10-04 02:00:58 -04001683 return __rb_page_index(iter->head_page, iter->head);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001684}
1685
Steven Rostedtbf41a152008-10-04 02:00:59 -04001686static inline unsigned rb_page_commit(struct buffer_page *bpage)
1687{
Steven Rostedtabc9b562008-12-02 15:34:06 -05001688 return local_read(&bpage->page->commit);
Steven Rostedtbf41a152008-10-04 02:00:59 -04001689}
1690
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001691/* Size is determined by what has been committed */
Steven Rostedtbf41a152008-10-04 02:00:59 -04001692static inline unsigned rb_page_size(struct buffer_page *bpage)
1693{
1694 return rb_page_commit(bpage);
1695}
1696
1697static inline unsigned
1698rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
1699{
1700 return rb_page_commit(cpu_buffer->commit_page);
1701}
1702
Steven Rostedtbf41a152008-10-04 02:00:59 -04001703static inline unsigned
1704rb_event_index(struct ring_buffer_event *event)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001705{
Steven Rostedtbf41a152008-10-04 02:00:59 -04001706 unsigned long addr = (unsigned long)event;
1707
Steven Rostedt22f470f2009-06-11 09:29:58 -04001708 return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001709}
1710
Steven Rostedt0f0c85f2009-05-11 16:08:00 -04001711static inline int
Steven Rostedtfa743952009-06-16 12:37:57 -04001712rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
1713 struct ring_buffer_event *event)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001714{
Steven Rostedtbf41a152008-10-04 02:00:59 -04001715 unsigned long addr = (unsigned long)event;
1716 unsigned long index;
1717
1718 index = rb_event_index(event);
1719 addr &= PAGE_MASK;
1720
1721 return cpu_buffer->commit_page->page == (void *)addr &&
1722 rb_commit_index(cpu_buffer) == index;
1723}
1724
Andrew Morton34a148b2009-01-09 12:27:09 -08001725static void
Steven Rostedtbf41a152008-10-04 02:00:59 -04001726rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
1727{
Steven Rostedt77ae3652009-03-27 11:00:29 -04001728 unsigned long max_count;
1729
Steven Rostedtbf41a152008-10-04 02:00:59 -04001730 /*
1731 * We only race with interrupts and NMIs on this CPU.
1732 * If we own the commit event, then we can commit
1733 * all others that interrupted us, since the interruptions
1734 * are in stack format (they finish before they come
1735 * back to us). This allows us to do a simple loop to
1736 * assign the commit to the tail.
1737 */
Steven Rostedta8ccf1d2008-12-23 11:32:24 -05001738 again:
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08001739 max_count = cpu_buffer->nr_pages * 100;
Steven Rostedt77ae3652009-03-27 11:00:29 -04001740
Steven Rostedtbf41a152008-10-04 02:00:59 -04001741 while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
Steven Rostedt77ae3652009-03-27 11:00:29 -04001742 if (RB_WARN_ON(cpu_buffer, !(--max_count)))
1743 return;
1744 if (RB_WARN_ON(cpu_buffer,
1745 rb_is_reader_page(cpu_buffer->tail_page)))
1746 return;
1747 local_set(&cpu_buffer->commit_page->page->commit,
1748 rb_page_write(cpu_buffer->commit_page));
Steven Rostedtbf41a152008-10-04 02:00:59 -04001749 rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
Steven Rostedtabc9b562008-12-02 15:34:06 -05001750 cpu_buffer->write_stamp =
1751 cpu_buffer->commit_page->page->time_stamp;
Steven Rostedtbf41a152008-10-04 02:00:59 -04001752 /* add barrier to keep gcc from optimizing too much */
1753 barrier();
1754 }
1755 while (rb_commit_index(cpu_buffer) !=
1756 rb_page_write(cpu_buffer->commit_page)) {
Steven Rostedt77ae3652009-03-27 11:00:29 -04001757
1758 local_set(&cpu_buffer->commit_page->page->commit,
1759 rb_page_write(cpu_buffer->commit_page));
1760 RB_WARN_ON(cpu_buffer,
1761 local_read(&cpu_buffer->commit_page->page->commit) &
1762 ~RB_WRITE_MASK);
Steven Rostedtbf41a152008-10-04 02:00:59 -04001763 barrier();
1764 }
Steven Rostedta8ccf1d2008-12-23 11:32:24 -05001765
1766 /* again, keep gcc from optimizing */
1767 barrier();
1768
1769 /*
1770 * If an interrupt came in just after the first while loop
1771 * and pushed the tail page forward, we will be left with
1772 * a dangling commit that will never go forward.
1773 */
1774 if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page))
1775 goto again;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001776}
1777
Steven Rostedtd7690412008-10-01 00:29:53 -04001778static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001779{
Steven Rostedtabc9b562008-12-02 15:34:06 -05001780 cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
Steven Rostedt6f807ac2008-10-04 02:00:58 -04001781 cpu_buffer->reader_page->read = 0;
Steven Rostedtd7690412008-10-01 00:29:53 -04001782}
1783
Andrew Morton34a148b2009-01-09 12:27:09 -08001784static void rb_inc_iter(struct ring_buffer_iter *iter)
Steven Rostedtd7690412008-10-01 00:29:53 -04001785{
1786 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
1787
1788 /*
1789 * The iterator could be on the reader page (it starts there).
1790 * But the head could have moved, since the reader was
1791 * found. Check for this case and assign the iterator
1792 * to the head page instead of next.
1793 */
1794 if (iter->head_page == cpu_buffer->reader_page)
Steven Rostedt77ae3652009-03-27 11:00:29 -04001795 iter->head_page = rb_set_head_page(cpu_buffer);
Steven Rostedtd7690412008-10-01 00:29:53 -04001796 else
1797 rb_inc_page(cpu_buffer, &iter->head_page);
1798
Steven Rostedtabc9b562008-12-02 15:34:06 -05001799 iter->read_stamp = iter->head_page->page->time_stamp;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001800 iter->head = 0;
1801}
1802
Steven Rostedt69d1b832010-10-07 18:18:05 -04001803/* Slow path, do not inline */
1804static noinline struct ring_buffer_event *
1805rb_add_time_stamp(struct ring_buffer_event *event, u64 delta)
1806{
1807 event->type_len = RINGBUF_TYPE_TIME_EXTEND;
1808
1809 /* Not the first event on the page? */
1810 if (rb_event_index(event)) {
1811 event->time_delta = delta & TS_MASK;
1812 event->array[0] = delta >> TS_SHIFT;
1813 } else {
1814 /* nope, just zero it */
1815 event->time_delta = 0;
1816 event->array[0] = 0;
1817 }
1818
1819 return skip_time_extend(event);
1820}
1821
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001822/**
1823 * ring_buffer_update_event - update event type and data
1824 * @event: the even to update
1825 * @type: the type of event
1826 * @length: the size of the event field in the ring buffer
1827 *
1828 * Update the type and data fields of the event. The length
1829 * is the actual size that is written to the ring buffer,
1830 * and with this, we can determine what to place into the
1831 * data field.
1832 */
Andrew Morton34a148b2009-01-09 12:27:09 -08001833static void
Steven Rostedt69d1b832010-10-07 18:18:05 -04001834rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
1835 struct ring_buffer_event *event, unsigned length,
1836 int add_timestamp, u64 delta)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001837{
Steven Rostedt69d1b832010-10-07 18:18:05 -04001838 /* Only a commit updates the timestamp */
1839 if (unlikely(!rb_event_is_commit(cpu_buffer, event)))
1840 delta = 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001841
Steven Rostedt69d1b832010-10-07 18:18:05 -04001842 /*
1843 * If we need to add a timestamp, then we
1844 * add it to the start of the resevered space.
1845 */
1846 if (unlikely(add_timestamp)) {
1847 event = rb_add_time_stamp(event, delta);
1848 length -= RB_LEN_TIME_EXTEND;
1849 delta = 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001850 }
Steven Rostedt69d1b832010-10-07 18:18:05 -04001851
1852 event->time_delta = delta;
1853 length -= RB_EVNT_HDR_SIZE;
1854 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
1855 event->type_len = 0;
1856 event->array[0] = length;
1857 } else
1858 event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04001859}
1860
Steven Rostedt77ae3652009-03-27 11:00:29 -04001861/*
1862 * rb_handle_head_page - writer hit the head page
1863 *
1864 * Returns: +1 to retry page
1865 * 0 to continue
1866 * -1 on error
1867 */
1868static int
1869rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
1870 struct buffer_page *tail_page,
1871 struct buffer_page *next_page)
1872{
1873 struct buffer_page *new_head;
1874 int entries;
1875 int type;
1876 int ret;
1877
1878 entries = rb_page_entries(next_page);
1879
1880 /*
1881 * The hard part is here. We need to move the head
1882 * forward, and protect against both readers on
1883 * other CPUs and writers coming in via interrupts.
1884 */
1885 type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
1886 RB_PAGE_HEAD);
1887
1888 /*
1889 * type can be one of four:
1890 * NORMAL - an interrupt already moved it for us
1891 * HEAD - we are the first to get here.
1892 * UPDATE - we are the interrupt interrupting
1893 * a current move.
1894 * MOVED - a reader on another CPU moved the next
1895 * pointer to its reader page. Give up
1896 * and try again.
1897 */
1898
1899 switch (type) {
1900 case RB_PAGE_HEAD:
1901 /*
1902 * We changed the head to UPDATE, thus
1903 * it is our responsibility to update
1904 * the counters.
1905 */
1906 local_add(entries, &cpu_buffer->overrun);
Vaibhav Nagarnaikc64e1482011-08-16 14:46:16 -07001907 local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes);
Steven Rostedt77ae3652009-03-27 11:00:29 -04001908
1909 /*
1910 * The entries will be zeroed out when we move the
1911 * tail page.
1912 */
1913
1914 /* still more to do */
1915 break;
1916
1917 case RB_PAGE_UPDATE:
1918 /*
1919 * This is an interrupt that interrupt the
1920 * previous update. Still more to do.
1921 */
1922 break;
1923 case RB_PAGE_NORMAL:
1924 /*
1925 * An interrupt came in before the update
1926 * and processed this for us.
1927 * Nothing left to do.
1928 */
1929 return 1;
1930 case RB_PAGE_MOVED:
1931 /*
1932 * The reader is on another CPU and just did
1933 * a swap with our next_page.
1934 * Try again.
1935 */
1936 return 1;
1937 default:
1938 RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
1939 return -1;
1940 }
1941
1942 /*
1943 * Now that we are here, the old head pointer is
1944 * set to UPDATE. This will keep the reader from
1945 * swapping the head page with the reader page.
1946 * The reader (on another CPU) will spin till
1947 * we are finished.
1948 *
1949 * We just need to protect against interrupts
1950 * doing the job. We will set the next pointer
1951 * to HEAD. After that, we set the old pointer
1952 * to NORMAL, but only if it was HEAD before.
1953 * otherwise we are an interrupt, and only
1954 * want the outer most commit to reset it.
1955 */
1956 new_head = next_page;
1957 rb_inc_page(cpu_buffer, &new_head);
1958
1959 ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
1960 RB_PAGE_NORMAL);
1961
1962 /*
1963 * Valid returns are:
1964 * HEAD - an interrupt came in and already set it.
1965 * NORMAL - One of two things:
1966 * 1) We really set it.
1967 * 2) A bunch of interrupts came in and moved
1968 * the page forward again.
1969 */
1970 switch (ret) {
1971 case RB_PAGE_HEAD:
1972 case RB_PAGE_NORMAL:
1973 /* OK */
1974 break;
1975 default:
1976 RB_WARN_ON(cpu_buffer, 1);
1977 return -1;
1978 }
1979
1980 /*
1981 * It is possible that an interrupt came in,
1982 * set the head up, then more interrupts came in
1983 * and moved it again. When we get back here,
1984 * the page would have been set to NORMAL but we
1985 * just set it back to HEAD.
1986 *
1987 * How do you detect this? Well, if that happened
1988 * the tail page would have moved.
1989 */
1990 if (ret == RB_PAGE_NORMAL) {
1991 /*
1992 * If the tail had moved passed next, then we need
1993 * to reset the pointer.
1994 */
1995 if (cpu_buffer->tail_page != tail_page &&
1996 cpu_buffer->tail_page != next_page)
1997 rb_head_page_set_normal(cpu_buffer, new_head,
1998 next_page,
1999 RB_PAGE_HEAD);
2000 }
2001
2002 /*
2003 * If this was the outer most commit (the one that
2004 * changed the original pointer from HEAD to UPDATE),
2005 * then it is up to us to reset it to NORMAL.
2006 */
2007 if (type == RB_PAGE_HEAD) {
2008 ret = rb_head_page_set_normal(cpu_buffer, next_page,
2009 tail_page,
2010 RB_PAGE_UPDATE);
2011 if (RB_WARN_ON(cpu_buffer,
2012 ret != RB_PAGE_UPDATE))
2013 return -1;
2014 }
2015
2016 return 0;
2017}
2018
Andrew Morton34a148b2009-01-09 12:27:09 -08002019static unsigned rb_calculate_event_length(unsigned length)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002020{
2021 struct ring_buffer_event event; /* Used only for sizeof array */
2022
2023 /* zero length can cause confusions */
2024 if (!length)
2025 length = 1;
2026
Steven Rostedt22710482010-03-18 17:54:19 -04002027 if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002028 length += sizeof(event.array[0]);
2029
2030 length += RB_EVNT_HDR_SIZE;
Steven Rostedt22710482010-03-18 17:54:19 -04002031 length = ALIGN(length, RB_ARCH_ALIGNMENT);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002032
2033 return length;
2034}
2035
Steven Rostedtc7b09302009-06-11 11:12:00 -04002036static inline void
2037rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
2038 struct buffer_page *tail_page,
2039 unsigned long tail, unsigned long length)
2040{
2041 struct ring_buffer_event *event;
2042
2043 /*
2044 * Only the event that crossed the page boundary
2045 * must fill the old tail_page with padding.
2046 */
2047 if (tail >= BUF_PAGE_SIZE) {
Steven Rostedtb3230c82010-05-21 11:55:21 -04002048 /*
2049 * If the page was filled, then we still need
2050 * to update the real_end. Reset it to zero
2051 * and the reader will ignore it.
2052 */
2053 if (tail == BUF_PAGE_SIZE)
2054 tail_page->real_end = 0;
2055
Steven Rostedtc7b09302009-06-11 11:12:00 -04002056 local_sub(length, &tail_page->write);
2057 return;
2058 }
2059
2060 event = __rb_page_index(tail_page, tail);
Linus Torvaldsb0b70652009-06-20 10:56:46 -07002061 kmemcheck_annotate_bitfield(event, bitfield);
Steven Rostedtc7b09302009-06-11 11:12:00 -04002062
Vaibhav Nagarnaikc64e1482011-08-16 14:46:16 -07002063 /* account for padding bytes */
2064 local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes);
2065
Steven Rostedtc7b09302009-06-11 11:12:00 -04002066 /*
Steven Rostedtff0ff842010-03-31 22:11:42 -04002067 * Save the original length to the meta data.
2068 * This will be used by the reader to add lost event
2069 * counter.
2070 */
2071 tail_page->real_end = tail;
2072
2073 /*
Steven Rostedtc7b09302009-06-11 11:12:00 -04002074 * If this event is bigger than the minimum size, then
2075 * we need to be careful that we don't subtract the
2076 * write counter enough to allow another writer to slip
2077 * in on this page.
2078 * We put in a discarded commit instead, to make sure
2079 * that this space is not used again.
2080 *
2081 * If we are less than the minimum size, we don't need to
2082 * worry about it.
2083 */
2084 if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
2085 /* No room for any events */
2086
2087 /* Mark the rest of the page with padding */
2088 rb_event_set_padding(event);
2089
2090 /* Set the write back to the previous setting */
2091 local_sub(length, &tail_page->write);
2092 return;
2093 }
2094
2095 /* Put in a discarded event */
2096 event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
2097 event->type_len = RINGBUF_TYPE_PADDING;
2098 /* time delta must be non zero */
2099 event->time_delta = 1;
Steven Rostedtc7b09302009-06-11 11:12:00 -04002100
2101 /* Set write to end of buffer */
2102 length = (tail + length) - BUF_PAGE_SIZE;
2103 local_sub(length, &tail_page->write);
2104}
Steven Rostedt6634ff22009-05-06 15:30:07 -04002105
Steven Rostedt747e94a2010-10-08 13:51:48 -04002106/*
2107 * This is the slow path, force gcc not to inline it.
2108 */
2109static noinline struct ring_buffer_event *
Steven Rostedt6634ff22009-05-06 15:30:07 -04002110rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
2111 unsigned long length, unsigned long tail,
Steven Rostedte8bc43e2010-10-20 10:58:02 -04002112 struct buffer_page *tail_page, u64 ts)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002113{
Steven Rostedt5a50e332009-11-17 08:43:01 -05002114 struct buffer_page *commit_page = cpu_buffer->commit_page;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002115 struct ring_buffer *buffer = cpu_buffer->buffer;
Steven Rostedt77ae3652009-03-27 11:00:29 -04002116 struct buffer_page *next_page;
2117 int ret;
Steven Rostedtaa20ae82009-05-05 21:16:11 -04002118
2119 next_page = tail_page;
2120
Steven Rostedtaa20ae82009-05-05 21:16:11 -04002121 rb_inc_page(cpu_buffer, &next_page);
2122
Steven Rostedtaa20ae82009-05-05 21:16:11 -04002123 /*
2124 * If for some reason, we had an interrupt storm that made
2125 * it all the way around the buffer, bail, and warn
2126 * about it.
2127 */
2128 if (unlikely(next_page == commit_page)) {
Steven Rostedt77ae3652009-03-27 11:00:29 -04002129 local_inc(&cpu_buffer->commit_overrun);
Steven Rostedtaa20ae82009-05-05 21:16:11 -04002130 goto out_reset;
2131 }
2132
Steven Rostedt77ae3652009-03-27 11:00:29 -04002133 /*
2134 * This is where the fun begins!
2135 *
2136 * We are fighting against races between a reader that
2137 * could be on another CPU trying to swap its reader
2138 * page with the buffer head.
2139 *
2140 * We are also fighting against interrupts coming in and
2141 * moving the head or tail on us as well.
2142 *
2143 * If the next page is the head page then we have filled
2144 * the buffer, unless the commit page is still on the
2145 * reader page.
2146 */
2147 if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
Steven Rostedtaa20ae82009-05-05 21:16:11 -04002148
Steven Rostedt77ae3652009-03-27 11:00:29 -04002149 /*
2150 * If the commit is not on the reader page, then
2151 * move the header page.
2152 */
2153 if (!rb_is_reader_page(cpu_buffer->commit_page)) {
2154 /*
2155 * If we are not in overwrite mode,
2156 * this is easy, just stop here.
2157 */
2158 if (!(buffer->flags & RB_FL_OVERWRITE))
2159 goto out_reset;
Steven Rostedtaa20ae82009-05-05 21:16:11 -04002160
Steven Rostedt77ae3652009-03-27 11:00:29 -04002161 ret = rb_handle_head_page(cpu_buffer,
2162 tail_page,
2163 next_page);
2164 if (ret < 0)
2165 goto out_reset;
2166 if (ret)
2167 goto out_again;
2168 } else {
2169 /*
2170 * We need to be careful here too. The
2171 * commit page could still be on the reader
2172 * page. We could have a small buffer, and
2173 * have filled up the buffer with events
2174 * from interrupts and such, and wrapped.
2175 *
2176 * Note, if the tail page is also the on the
2177 * reader_page, we let it move out.
2178 */
2179 if (unlikely((cpu_buffer->commit_page !=
2180 cpu_buffer->tail_page) &&
2181 (cpu_buffer->commit_page ==
2182 cpu_buffer->reader_page))) {
2183 local_inc(&cpu_buffer->commit_overrun);
2184 goto out_reset;
2185 }
Steven Rostedtaa20ae82009-05-05 21:16:11 -04002186 }
2187 }
2188
Steven Rostedt77ae3652009-03-27 11:00:29 -04002189 ret = rb_tail_page_update(cpu_buffer, tail_page, next_page);
2190 if (ret) {
2191 /*
2192 * Nested commits always have zero deltas, so
2193 * just reread the time stamp
2194 */
Steven Rostedte8bc43e2010-10-20 10:58:02 -04002195 ts = rb_time_stamp(buffer);
2196 next_page->page->time_stamp = ts;
Steven Rostedtaa20ae82009-05-05 21:16:11 -04002197 }
2198
Steven Rostedt77ae3652009-03-27 11:00:29 -04002199 out_again:
Steven Rostedtaa20ae82009-05-05 21:16:11 -04002200
Steven Rostedt77ae3652009-03-27 11:00:29 -04002201 rb_reset_tail(cpu_buffer, tail_page, tail, length);
Steven Rostedtaa20ae82009-05-05 21:16:11 -04002202
2203 /* fail and let the caller try again */
2204 return ERR_PTR(-EAGAIN);
2205
Steven Rostedt45141d42009-02-12 13:19:48 -05002206 out_reset:
Lai Jiangshan6f3b3442009-01-12 11:06:18 +08002207 /* reset write */
Steven Rostedtc7b09302009-06-11 11:12:00 -04002208 rb_reset_tail(cpu_buffer, tail_page, tail, length);
Lai Jiangshan6f3b3442009-01-12 11:06:18 +08002209
Steven Rostedtbf41a152008-10-04 02:00:59 -04002210 return NULL;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002211}
2212
Steven Rostedt6634ff22009-05-06 15:30:07 -04002213static struct ring_buffer_event *
2214__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
Steven Rostedt69d1b832010-10-07 18:18:05 -04002215 unsigned long length, u64 ts,
2216 u64 delta, int add_timestamp)
Steven Rostedt6634ff22009-05-06 15:30:07 -04002217{
Steven Rostedt5a50e332009-11-17 08:43:01 -05002218 struct buffer_page *tail_page;
Steven Rostedt6634ff22009-05-06 15:30:07 -04002219 struct ring_buffer_event *event;
2220 unsigned long tail, write;
2221
Steven Rostedt69d1b832010-10-07 18:18:05 -04002222 /*
2223 * If the time delta since the last event is too big to
2224 * hold in the time field of the event, then we append a
2225 * TIME EXTEND event ahead of the data event.
2226 */
2227 if (unlikely(add_timestamp))
2228 length += RB_LEN_TIME_EXTEND;
2229
Steven Rostedt6634ff22009-05-06 15:30:07 -04002230 tail_page = cpu_buffer->tail_page;
2231 write = local_add_return(length, &tail_page->write);
Steven Rostedt77ae3652009-03-27 11:00:29 -04002232
2233 /* set write to only the index of the write */
2234 write &= RB_WRITE_MASK;
Steven Rostedt6634ff22009-05-06 15:30:07 -04002235 tail = write - length;
2236
2237 /* See if we shot pass the end of this buffer page */
Steven Rostedt747e94a2010-10-08 13:51:48 -04002238 if (unlikely(write > BUF_PAGE_SIZE))
Steven Rostedt6634ff22009-05-06 15:30:07 -04002239 return rb_move_tail(cpu_buffer, length, tail,
Steven Rostedt5a50e332009-11-17 08:43:01 -05002240 tail_page, ts);
Steven Rostedt6634ff22009-05-06 15:30:07 -04002241
2242 /* We reserved something on the buffer */
2243
Steven Rostedt6634ff22009-05-06 15:30:07 -04002244 event = __rb_page_index(tail_page, tail);
Vegard Nossum1744a212009-02-28 08:29:44 +01002245 kmemcheck_annotate_bitfield(event, bitfield);
Steven Rostedt69d1b832010-10-07 18:18:05 -04002246 rb_update_event(cpu_buffer, event, length, add_timestamp, delta);
Steven Rostedt6634ff22009-05-06 15:30:07 -04002247
Steven Rostedt69d1b832010-10-07 18:18:05 -04002248 local_inc(&tail_page->entries);
Steven Rostedt6634ff22009-05-06 15:30:07 -04002249
2250 /*
Steven Rostedtfa743952009-06-16 12:37:57 -04002251 * If this is the first commit on the page, then update
2252 * its timestamp.
Steven Rostedt6634ff22009-05-06 15:30:07 -04002253 */
Steven Rostedtfa743952009-06-16 12:37:57 -04002254 if (!tail)
Steven Rostedte8bc43e2010-10-20 10:58:02 -04002255 tail_page->page->time_stamp = ts;
Steven Rostedt6634ff22009-05-06 15:30:07 -04002256
Vaibhav Nagarnaikc64e1482011-08-16 14:46:16 -07002257 /* account for these added bytes */
2258 local_add(length, &cpu_buffer->entries_bytes);
2259
Steven Rostedt6634ff22009-05-06 15:30:07 -04002260 return event;
2261}
2262
Steven Rostedtedd813bf2009-06-02 23:00:53 -04002263static inline int
2264rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
2265 struct ring_buffer_event *event)
2266{
2267 unsigned long new_index, old_index;
2268 struct buffer_page *bpage;
2269 unsigned long index;
2270 unsigned long addr;
2271
2272 new_index = rb_event_index(event);
Steven Rostedt69d1b832010-10-07 18:18:05 -04002273 old_index = new_index + rb_event_ts_length(event);
Steven Rostedtedd813bf2009-06-02 23:00:53 -04002274 addr = (unsigned long)event;
2275 addr &= PAGE_MASK;
2276
2277 bpage = cpu_buffer->tail_page;
2278
2279 if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
Steven Rostedt77ae3652009-03-27 11:00:29 -04002280 unsigned long write_mask =
2281 local_read(&bpage->write) & ~RB_WRITE_MASK;
Vaibhav Nagarnaikc64e1482011-08-16 14:46:16 -07002282 unsigned long event_length = rb_event_length(event);
Steven Rostedtedd813bf2009-06-02 23:00:53 -04002283 /*
2284 * This is on the tail page. It is possible that
2285 * a write could come in and move the tail page
2286 * and write to the next page. That is fine
2287 * because we just shorten what is on this page.
2288 */
Steven Rostedt77ae3652009-03-27 11:00:29 -04002289 old_index += write_mask;
2290 new_index += write_mask;
Steven Rostedtedd813bf2009-06-02 23:00:53 -04002291 index = local_cmpxchg(&bpage->write, old_index, new_index);
Vaibhav Nagarnaikc64e1482011-08-16 14:46:16 -07002292 if (index == old_index) {
2293 /* update counters */
2294 local_sub(event_length, &cpu_buffer->entries_bytes);
Steven Rostedtedd813bf2009-06-02 23:00:53 -04002295 return 1;
Vaibhav Nagarnaikc64e1482011-08-16 14:46:16 -07002296 }
Steven Rostedtedd813bf2009-06-02 23:00:53 -04002297 }
2298
2299 /* could not discard */
2300 return 0;
2301}
2302
Steven Rostedtfa743952009-06-16 12:37:57 -04002303static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
2304{
2305 local_inc(&cpu_buffer->committing);
2306 local_inc(&cpu_buffer->commits);
2307}
2308
Steven Rostedtd9abde22010-10-19 13:17:08 -04002309static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
Steven Rostedtfa743952009-06-16 12:37:57 -04002310{
2311 unsigned long commits;
2312
2313 if (RB_WARN_ON(cpu_buffer,
2314 !local_read(&cpu_buffer->committing)))
2315 return;
2316
2317 again:
2318 commits = local_read(&cpu_buffer->commits);
2319 /* synchronize with interrupts */
2320 barrier();
2321 if (local_read(&cpu_buffer->committing) == 1)
2322 rb_set_commit_to_write(cpu_buffer);
2323
2324 local_dec(&cpu_buffer->committing);
2325
2326 /* synchronize with interrupts */
2327 barrier();
2328
2329 /*
2330 * Need to account for interrupts coming in between the
2331 * updating of the commit page and the clearing of the
2332 * committing counter.
2333 */
2334 if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
2335 !local_read(&cpu_buffer->committing)) {
2336 local_inc(&cpu_buffer->committing);
2337 goto again;
2338 }
2339}
2340
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002341static struct ring_buffer_event *
Steven Rostedt62f0b3e2009-09-04 14:11:34 -04002342rb_reserve_next_event(struct ring_buffer *buffer,
2343 struct ring_buffer_per_cpu *cpu_buffer,
Steven Rostedt1cd8d732009-05-11 14:08:09 -04002344 unsigned long length)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002345{
2346 struct ring_buffer_event *event;
Steven Rostedt69d1b832010-10-07 18:18:05 -04002347 u64 ts, delta;
Steven Rostedt818e3dd2008-10-31 09:58:35 -04002348 int nr_loops = 0;
Steven Rostedt69d1b832010-10-07 18:18:05 -04002349 int add_timestamp;
Steven Rostedt140ff892010-10-08 10:50:30 -04002350 u64 diff;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002351
Steven Rostedtfa743952009-06-16 12:37:57 -04002352 rb_start_commit(cpu_buffer);
2353
Steven Rostedt85bac322009-09-04 14:24:40 -04002354#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
Steven Rostedt62f0b3e2009-09-04 14:11:34 -04002355 /*
2356 * Due to the ability to swap a cpu buffer from a buffer
2357 * it is possible it was swapped before we committed.
2358 * (committing stops a swap). We check for it here and
2359 * if it happened, we have to fail the write.
2360 */
2361 barrier();
2362 if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) {
2363 local_dec(&cpu_buffer->committing);
2364 local_dec(&cpu_buffer->commits);
2365 return NULL;
2366 }
Steven Rostedt85bac322009-09-04 14:24:40 -04002367#endif
Steven Rostedt62f0b3e2009-09-04 14:11:34 -04002368
Steven Rostedtbe957c42009-05-11 14:42:53 -04002369 length = rb_calculate_event_length(length);
Steven Rostedtbf41a152008-10-04 02:00:59 -04002370 again:
Steven Rostedt69d1b832010-10-07 18:18:05 -04002371 add_timestamp = 0;
2372 delta = 0;
2373
Steven Rostedt818e3dd2008-10-31 09:58:35 -04002374 /*
2375 * We allow for interrupts to reenter here and do a trace.
2376 * If one does, it will cause this original code to loop
2377 * back here. Even with heavy interrupts happening, this
2378 * should only happen a few times in a row. If this happens
2379 * 1000 times in a row, there must be either an interrupt
2380 * storm or we have something buggy.
2381 * Bail!
2382 */
Steven Rostedt3e89c7b2008-11-11 15:28:41 -05002383 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
Steven Rostedtfa743952009-06-16 12:37:57 -04002384 goto out_fail;
Steven Rostedt818e3dd2008-10-31 09:58:35 -04002385
Jiri Olsa6d3f1e12009-10-23 19:36:19 -04002386 ts = rb_time_stamp(cpu_buffer->buffer);
Steven Rostedt140ff892010-10-08 10:50:30 -04002387 diff = ts - cpu_buffer->write_stamp;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002388
Steven Rostedt140ff892010-10-08 10:50:30 -04002389 /* make sure this diff is calculated here */
2390 barrier();
Steven Rostedtbf41a152008-10-04 02:00:59 -04002391
Steven Rostedt140ff892010-10-08 10:50:30 -04002392 /* Did the write stamp get updated already? */
2393 if (likely(ts >= cpu_buffer->write_stamp)) {
Steven Rostedt168b6b12009-05-11 22:11:05 -04002394 delta = diff;
2395 if (unlikely(test_time_stamp(delta))) {
Jiri Olsa31274d72011-02-18 15:52:19 +01002396 int local_clock_stable = 1;
2397#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
2398 local_clock_stable = sched_clock_stable;
2399#endif
Steven Rostedt69d1b832010-10-07 18:18:05 -04002400 WARN_ONCE(delta > (1ULL << 59),
Jiri Olsa31274d72011-02-18 15:52:19 +01002401 KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s",
Steven Rostedt69d1b832010-10-07 18:18:05 -04002402 (unsigned long long)delta,
2403 (unsigned long long)ts,
Jiri Olsa31274d72011-02-18 15:52:19 +01002404 (unsigned long long)cpu_buffer->write_stamp,
2405 local_clock_stable ? "" :
2406 "If you just came from a suspend/resume,\n"
2407 "please switch to the trace global clock:\n"
2408 " echo global > /sys/kernel/debug/tracing/trace_clock\n");
Steven Rostedt69d1b832010-10-07 18:18:05 -04002409 add_timestamp = 1;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002410 }
Steven Rostedt168b6b12009-05-11 22:11:05 -04002411 }
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002412
Steven Rostedt69d1b832010-10-07 18:18:05 -04002413 event = __rb_reserve_next(cpu_buffer, length, ts,
2414 delta, add_timestamp);
Steven Rostedt168b6b12009-05-11 22:11:05 -04002415 if (unlikely(PTR_ERR(event) == -EAGAIN))
Steven Rostedtbf41a152008-10-04 02:00:59 -04002416 goto again;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002417
Steven Rostedtfa743952009-06-16 12:37:57 -04002418 if (!event)
2419 goto out_fail;
Steven Rostedtbf41a152008-10-04 02:00:59 -04002420
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002421 return event;
Steven Rostedtfa743952009-06-16 12:37:57 -04002422
2423 out_fail:
2424 rb_end_commit(cpu_buffer);
2425 return NULL;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002426}
2427
Paul Mundt1155de42009-06-25 14:30:12 +09002428#ifdef CONFIG_TRACING
2429
Steven Rostedtaa18efb2009-04-20 16:16:11 -04002430#define TRACE_RECURSIVE_DEPTH 16
Steven Rostedt261842b2009-04-16 21:41:52 -04002431
Steven Rostedtd9abde22010-10-19 13:17:08 -04002432/* Keep this code out of the fast path cache */
2433static noinline void trace_recursive_fail(void)
Steven Rostedt261842b2009-04-16 21:41:52 -04002434{
Steven Rostedtaa18efb2009-04-20 16:16:11 -04002435 /* Disable all tracing before we do anything else */
2436 tracing_off_permanent();
Frederic Weisbeckere057a5e2009-04-19 23:38:12 +02002437
Steven Rostedt7d7d2b82009-04-27 12:37:49 -04002438 printk_once(KERN_WARNING "Tracing recursion: depth[%ld]:"
Steven Rostedtaa18efb2009-04-20 16:16:11 -04002439 "HC[%lu]:SC[%lu]:NMI[%lu]\n",
Steven Rostedtb1cff0a2011-05-25 14:27:43 -04002440 trace_recursion_buffer(),
Steven Rostedtaa18efb2009-04-20 16:16:11 -04002441 hardirq_count() >> HARDIRQ_SHIFT,
2442 softirq_count() >> SOFTIRQ_SHIFT,
2443 in_nmi());
Frederic Weisbeckere057a5e2009-04-19 23:38:12 +02002444
Steven Rostedtaa18efb2009-04-20 16:16:11 -04002445 WARN_ON_ONCE(1);
Steven Rostedtd9abde22010-10-19 13:17:08 -04002446}
2447
2448static inline int trace_recursive_lock(void)
2449{
Steven Rostedtb1cff0a2011-05-25 14:27:43 -04002450 trace_recursion_inc();
Steven Rostedtd9abde22010-10-19 13:17:08 -04002451
Steven Rostedtb1cff0a2011-05-25 14:27:43 -04002452 if (likely(trace_recursion_buffer() < TRACE_RECURSIVE_DEPTH))
Steven Rostedtd9abde22010-10-19 13:17:08 -04002453 return 0;
2454
2455 trace_recursive_fail();
2456
Steven Rostedtaa18efb2009-04-20 16:16:11 -04002457 return -1;
Steven Rostedt261842b2009-04-16 21:41:52 -04002458}
2459
Steven Rostedtd9abde22010-10-19 13:17:08 -04002460static inline void trace_recursive_unlock(void)
Steven Rostedt261842b2009-04-16 21:41:52 -04002461{
Steven Rostedtb1cff0a2011-05-25 14:27:43 -04002462 WARN_ON_ONCE(!trace_recursion_buffer());
Steven Rostedt261842b2009-04-16 21:41:52 -04002463
Steven Rostedtb1cff0a2011-05-25 14:27:43 -04002464 trace_recursion_dec();
Steven Rostedt261842b2009-04-16 21:41:52 -04002465}
2466
Paul Mundt1155de42009-06-25 14:30:12 +09002467#else
2468
2469#define trace_recursive_lock() (0)
2470#define trace_recursive_unlock() do { } while (0)
2471
2472#endif
2473
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002474/**
2475 * ring_buffer_lock_reserve - reserve a part of the buffer
2476 * @buffer: the ring buffer to reserve from
2477 * @length: the length of the data to reserve (excluding event header)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002478 *
2479 * Returns a reseverd event on the ring buffer to copy directly to.
2480 * The user of this interface will need to get the body to write into
2481 * and can use the ring_buffer_event_data() interface.
2482 *
2483 * The length is the length of the data needed, not the event length
2484 * which also includes the event header.
2485 *
2486 * Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
2487 * If NULL is returned, then nothing has been allocated or locked.
2488 */
2489struct ring_buffer_event *
Arnaldo Carvalho de Melo0a987752009-02-05 16:12:56 -02002490ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002491{
2492 struct ring_buffer_per_cpu *cpu_buffer;
2493 struct ring_buffer_event *event;
Steven Rostedt5168ae52010-06-03 09:36:50 -04002494 int cpu;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002495
Steven Rostedt033601a2008-11-21 12:41:55 -05002496 if (ring_buffer_flags != RB_BUFFERS_ON)
Steven Rostedta3583242008-11-11 15:01:42 -05002497 return NULL;
2498
Steven Rostedtbf41a152008-10-04 02:00:59 -04002499 /* If we are tracing schedule, we don't want to recurse */
Steven Rostedt5168ae52010-06-03 09:36:50 -04002500 preempt_disable_notrace();
Steven Rostedtbf41a152008-10-04 02:00:59 -04002501
Lai Jiangshan52fbe9c2010-03-08 14:50:43 +08002502 if (atomic_read(&buffer->record_disabled))
2503 goto out_nocheck;
2504
Steven Rostedt261842b2009-04-16 21:41:52 -04002505 if (trace_recursive_lock())
2506 goto out_nocheck;
2507
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002508 cpu = raw_smp_processor_id();
2509
Rusty Russell9e01c1b2009-01-01 10:12:22 +10302510 if (!cpumask_test_cpu(cpu, buffer->cpumask))
Steven Rostedtd7690412008-10-01 00:29:53 -04002511 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002512
2513 cpu_buffer = buffer->buffers[cpu];
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002514
2515 if (atomic_read(&cpu_buffer->record_disabled))
Steven Rostedtd7690412008-10-01 00:29:53 -04002516 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002517
Steven Rostedtbe957c42009-05-11 14:42:53 -04002518 if (length > BUF_MAX_DATA_SIZE)
Steven Rostedtbf41a152008-10-04 02:00:59 -04002519 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002520
Steven Rostedt62f0b3e2009-09-04 14:11:34 -04002521 event = rb_reserve_next_event(buffer, cpu_buffer, length);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002522 if (!event)
Steven Rostedtd7690412008-10-01 00:29:53 -04002523 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002524
2525 return event;
2526
Steven Rostedtd7690412008-10-01 00:29:53 -04002527 out:
Steven Rostedt261842b2009-04-16 21:41:52 -04002528 trace_recursive_unlock();
2529
2530 out_nocheck:
Steven Rostedt5168ae52010-06-03 09:36:50 -04002531 preempt_enable_notrace();
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002532 return NULL;
2533}
Robert Richterc4f50182008-12-11 16:49:22 +01002534EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002535
Steven Rostedta1863c22009-09-03 10:23:58 -04002536static void
2537rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002538 struct ring_buffer_event *event)
2539{
Steven Rostedt69d1b832010-10-07 18:18:05 -04002540 u64 delta;
2541
Steven Rostedtfa743952009-06-16 12:37:57 -04002542 /*
2543 * The event first in the commit queue updates the
2544 * time stamp.
2545 */
Steven Rostedt69d1b832010-10-07 18:18:05 -04002546 if (rb_event_is_commit(cpu_buffer, event)) {
2547 /*
2548 * A commit event that is first on a page
2549 * updates the write timestamp with the page stamp
2550 */
2551 if (!rb_event_index(event))
2552 cpu_buffer->write_stamp =
2553 cpu_buffer->commit_page->page->time_stamp;
2554 else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) {
2555 delta = event->array[0];
2556 delta <<= TS_SHIFT;
2557 delta += event->time_delta;
2558 cpu_buffer->write_stamp += delta;
2559 } else
2560 cpu_buffer->write_stamp += event->time_delta;
2561 }
Steven Rostedta1863c22009-09-03 10:23:58 -04002562}
Steven Rostedtbf41a152008-10-04 02:00:59 -04002563
Steven Rostedta1863c22009-09-03 10:23:58 -04002564static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
2565 struct ring_buffer_event *event)
2566{
2567 local_inc(&cpu_buffer->entries);
2568 rb_update_write_stamp(cpu_buffer, event);
Steven Rostedtfa743952009-06-16 12:37:57 -04002569 rb_end_commit(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002570}
2571
2572/**
2573 * ring_buffer_unlock_commit - commit a reserved
2574 * @buffer: The buffer to commit to
2575 * @event: The event pointer to commit.
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002576 *
2577 * This commits the data to the ring buffer, and releases any locks held.
2578 *
2579 * Must be paired with ring_buffer_lock_reserve.
2580 */
2581int ring_buffer_unlock_commit(struct ring_buffer *buffer,
Arnaldo Carvalho de Melo0a987752009-02-05 16:12:56 -02002582 struct ring_buffer_event *event)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002583{
2584 struct ring_buffer_per_cpu *cpu_buffer;
2585 int cpu = raw_smp_processor_id();
2586
2587 cpu_buffer = buffer->buffers[cpu];
2588
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002589 rb_commit(cpu_buffer, event);
2590
Steven Rostedt261842b2009-04-16 21:41:52 -04002591 trace_recursive_unlock();
2592
Steven Rostedt5168ae52010-06-03 09:36:50 -04002593 preempt_enable_notrace();
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002594
2595 return 0;
2596}
Robert Richterc4f50182008-12-11 16:49:22 +01002597EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002598
Frederic Weisbeckerf3b9aae2009-04-19 23:39:33 +02002599static inline void rb_event_discard(struct ring_buffer_event *event)
2600{
Steven Rostedt69d1b832010-10-07 18:18:05 -04002601 if (event->type_len == RINGBUF_TYPE_TIME_EXTEND)
2602 event = skip_time_extend(event);
2603
Lai Jiangshan334d4162009-04-24 11:27:05 +08002604 /* array[0] holds the actual length for the discarded event */
2605 event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
2606 event->type_len = RINGBUF_TYPE_PADDING;
Frederic Weisbeckerf3b9aae2009-04-19 23:39:33 +02002607 /* time delta must be non zero */
2608 if (!event->time_delta)
2609 event->time_delta = 1;
2610}
2611
Steven Rostedta1863c22009-09-03 10:23:58 -04002612/*
2613 * Decrement the entries to the page that an event is on.
2614 * The event does not even need to exist, only the pointer
2615 * to the page it is on. This may only be called before the commit
2616 * takes place.
2617 */
2618static inline void
2619rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
2620 struct ring_buffer_event *event)
2621{
2622 unsigned long addr = (unsigned long)event;
2623 struct buffer_page *bpage = cpu_buffer->commit_page;
2624 struct buffer_page *start;
2625
2626 addr &= PAGE_MASK;
2627
2628 /* Do the likely case first */
2629 if (likely(bpage->page == (void *)addr)) {
2630 local_dec(&bpage->entries);
2631 return;
2632 }
2633
2634 /*
2635 * Because the commit page may be on the reader page we
2636 * start with the next page and check the end loop there.
2637 */
2638 rb_inc_page(cpu_buffer, &bpage);
2639 start = bpage;
2640 do {
2641 if (bpage->page == (void *)addr) {
2642 local_dec(&bpage->entries);
2643 return;
2644 }
2645 rb_inc_page(cpu_buffer, &bpage);
2646 } while (bpage != start);
2647
2648 /* commit not part of this buffer?? */
2649 RB_WARN_ON(cpu_buffer, 1);
2650}
2651
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002652/**
Steven Rostedtfa1b47d2009-04-02 00:09:41 -04002653 * ring_buffer_commit_discard - discard an event that has not been committed
2654 * @buffer: the ring buffer
2655 * @event: non committed event to discard
2656 *
Steven Rostedtdc892f72009-09-03 15:33:41 -04002657 * Sometimes an event that is in the ring buffer needs to be ignored.
2658 * This function lets the user discard an event in the ring buffer
2659 * and then that event will not be read later.
2660 *
2661 * This function only works if it is called before the the item has been
2662 * committed. It will try to free the event from the ring buffer
Steven Rostedtfa1b47d2009-04-02 00:09:41 -04002663 * if another event has not been added behind it.
2664 *
2665 * If another event has been added behind it, it will set the event
2666 * up as discarded, and perform the commit.
2667 *
2668 * If this function is called, do not call ring_buffer_unlock_commit on
2669 * the event.
2670 */
2671void ring_buffer_discard_commit(struct ring_buffer *buffer,
2672 struct ring_buffer_event *event)
2673{
2674 struct ring_buffer_per_cpu *cpu_buffer;
Steven Rostedtfa1b47d2009-04-02 00:09:41 -04002675 int cpu;
2676
2677 /* The event is discarded regardless */
Frederic Weisbeckerf3b9aae2009-04-19 23:39:33 +02002678 rb_event_discard(event);
Steven Rostedtfa1b47d2009-04-02 00:09:41 -04002679
Steven Rostedtfa743952009-06-16 12:37:57 -04002680 cpu = smp_processor_id();
2681 cpu_buffer = buffer->buffers[cpu];
2682
Steven Rostedtfa1b47d2009-04-02 00:09:41 -04002683 /*
2684 * This must only be called if the event has not been
2685 * committed yet. Thus we can assume that preemption
2686 * is still disabled.
2687 */
Steven Rostedtfa743952009-06-16 12:37:57 -04002688 RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
Steven Rostedtfa1b47d2009-04-02 00:09:41 -04002689
Steven Rostedta1863c22009-09-03 10:23:58 -04002690 rb_decrement_entry(cpu_buffer, event);
Steven Rostedt0f2541d2009-08-05 12:02:48 -04002691 if (rb_try_to_discard(cpu_buffer, event))
Steven Rostedtedd813bf2009-06-02 23:00:53 -04002692 goto out;
Steven Rostedtfa1b47d2009-04-02 00:09:41 -04002693
2694 /*
2695 * The commit is still visible by the reader, so we
Steven Rostedta1863c22009-09-03 10:23:58 -04002696 * must still update the timestamp.
Steven Rostedtfa1b47d2009-04-02 00:09:41 -04002697 */
Steven Rostedta1863c22009-09-03 10:23:58 -04002698 rb_update_write_stamp(cpu_buffer, event);
Steven Rostedtfa1b47d2009-04-02 00:09:41 -04002699 out:
Steven Rostedtfa743952009-06-16 12:37:57 -04002700 rb_end_commit(cpu_buffer);
Steven Rostedtfa1b47d2009-04-02 00:09:41 -04002701
Frederic Weisbeckerf3b9aae2009-04-19 23:39:33 +02002702 trace_recursive_unlock();
2703
Steven Rostedt5168ae52010-06-03 09:36:50 -04002704 preempt_enable_notrace();
Steven Rostedtfa1b47d2009-04-02 00:09:41 -04002705
2706}
2707EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
2708
2709/**
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002710 * ring_buffer_write - write data to the buffer without reserving
2711 * @buffer: The ring buffer to write to.
2712 * @length: The length of the data being written (excluding the event header)
2713 * @data: The data to write to the buffer.
2714 *
2715 * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
2716 * one function. If you already have the data to write to the buffer, it
2717 * may be easier to simply call this function.
2718 *
2719 * Note, like ring_buffer_lock_reserve, the length is the length of the data
2720 * and not the length of the event which would hold the header.
2721 */
2722int ring_buffer_write(struct ring_buffer *buffer,
2723 unsigned long length,
2724 void *data)
2725{
2726 struct ring_buffer_per_cpu *cpu_buffer;
2727 struct ring_buffer_event *event;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002728 void *body;
2729 int ret = -EBUSY;
Steven Rostedt5168ae52010-06-03 09:36:50 -04002730 int cpu;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002731
Steven Rostedt033601a2008-11-21 12:41:55 -05002732 if (ring_buffer_flags != RB_BUFFERS_ON)
Steven Rostedta3583242008-11-11 15:01:42 -05002733 return -EBUSY;
2734
Steven Rostedt5168ae52010-06-03 09:36:50 -04002735 preempt_disable_notrace();
Steven Rostedtbf41a152008-10-04 02:00:59 -04002736
Lai Jiangshan52fbe9c2010-03-08 14:50:43 +08002737 if (atomic_read(&buffer->record_disabled))
2738 goto out;
2739
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002740 cpu = raw_smp_processor_id();
2741
Rusty Russell9e01c1b2009-01-01 10:12:22 +10302742 if (!cpumask_test_cpu(cpu, buffer->cpumask))
Steven Rostedtd7690412008-10-01 00:29:53 -04002743 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002744
2745 cpu_buffer = buffer->buffers[cpu];
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002746
2747 if (atomic_read(&cpu_buffer->record_disabled))
2748 goto out;
2749
Steven Rostedtbe957c42009-05-11 14:42:53 -04002750 if (length > BUF_MAX_DATA_SIZE)
2751 goto out;
2752
Steven Rostedt62f0b3e2009-09-04 14:11:34 -04002753 event = rb_reserve_next_event(buffer, cpu_buffer, length);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002754 if (!event)
2755 goto out;
2756
2757 body = rb_event_data(event);
2758
2759 memcpy(body, data, length);
2760
2761 rb_commit(cpu_buffer, event);
2762
2763 ret = 0;
2764 out:
Steven Rostedt5168ae52010-06-03 09:36:50 -04002765 preempt_enable_notrace();
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002766
2767 return ret;
2768}
Robert Richterc4f50182008-12-11 16:49:22 +01002769EXPORT_SYMBOL_GPL(ring_buffer_write);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002770
Andrew Morton34a148b2009-01-09 12:27:09 -08002771static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
Steven Rostedtbf41a152008-10-04 02:00:59 -04002772{
2773 struct buffer_page *reader = cpu_buffer->reader_page;
Steven Rostedt77ae3652009-03-27 11:00:29 -04002774 struct buffer_page *head = rb_set_head_page(cpu_buffer);
Steven Rostedtbf41a152008-10-04 02:00:59 -04002775 struct buffer_page *commit = cpu_buffer->commit_page;
2776
Steven Rostedt77ae3652009-03-27 11:00:29 -04002777 /* In case of error, head will be NULL */
2778 if (unlikely(!head))
2779 return 1;
2780
Steven Rostedtbf41a152008-10-04 02:00:59 -04002781 return reader->read == rb_page_commit(reader) &&
2782 (commit == reader ||
2783 (commit == head &&
2784 head->read == rb_page_commit(commit)));
2785}
2786
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002787/**
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002788 * ring_buffer_record_disable - stop all writes into the buffer
2789 * @buffer: The ring buffer to stop writes to.
2790 *
2791 * This prevents all writes to the buffer. Any attempt to write
2792 * to the buffer after this will fail and return NULL.
2793 *
2794 * The caller should call synchronize_sched() after this.
2795 */
2796void ring_buffer_record_disable(struct ring_buffer *buffer)
2797{
2798 atomic_inc(&buffer->record_disabled);
2799}
Robert Richterc4f50182008-12-11 16:49:22 +01002800EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002801
2802/**
2803 * ring_buffer_record_enable - enable writes to the buffer
2804 * @buffer: The ring buffer to enable writes
2805 *
2806 * Note, multiple disables will need the same number of enables
Adam Buchbinderc41b20e2009-12-11 16:35:39 -05002807 * to truly enable the writing (much like preempt_disable).
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002808 */
2809void ring_buffer_record_enable(struct ring_buffer *buffer)
2810{
2811 atomic_dec(&buffer->record_disabled);
2812}
Robert Richterc4f50182008-12-11 16:49:22 +01002813EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002814
2815/**
Steven Rostedt499e5472012-02-22 15:50:28 -05002816 * ring_buffer_record_off - stop all writes into the buffer
2817 * @buffer: The ring buffer to stop writes to.
2818 *
2819 * This prevents all writes to the buffer. Any attempt to write
2820 * to the buffer after this will fail and return NULL.
2821 *
2822 * This is different than ring_buffer_record_disable() as
Wang Tianhong87abb3b2012-08-02 14:02:00 +08002823 * it works like an on/off switch, where as the disable() version
Steven Rostedt499e5472012-02-22 15:50:28 -05002824 * must be paired with a enable().
2825 */
2826void ring_buffer_record_off(struct ring_buffer *buffer)
2827{
2828 unsigned int rd;
2829 unsigned int new_rd;
2830
2831 do {
2832 rd = atomic_read(&buffer->record_disabled);
2833 new_rd = rd | RB_BUFFER_OFF;
2834 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
2835}
2836EXPORT_SYMBOL_GPL(ring_buffer_record_off);
2837
2838/**
2839 * ring_buffer_record_on - restart writes into the buffer
2840 * @buffer: The ring buffer to start writes to.
2841 *
2842 * This enables all writes to the buffer that was disabled by
2843 * ring_buffer_record_off().
2844 *
2845 * This is different than ring_buffer_record_enable() as
Wang Tianhong87abb3b2012-08-02 14:02:00 +08002846 * it works like an on/off switch, where as the enable() version
Steven Rostedt499e5472012-02-22 15:50:28 -05002847 * must be paired with a disable().
2848 */
2849void ring_buffer_record_on(struct ring_buffer *buffer)
2850{
2851 unsigned int rd;
2852 unsigned int new_rd;
2853
2854 do {
2855 rd = atomic_read(&buffer->record_disabled);
2856 new_rd = rd & ~RB_BUFFER_OFF;
2857 } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
2858}
2859EXPORT_SYMBOL_GPL(ring_buffer_record_on);
2860
2861/**
2862 * ring_buffer_record_is_on - return true if the ring buffer can write
2863 * @buffer: The ring buffer to see if write is enabled
2864 *
2865 * Returns true if the ring buffer is in a state that it accepts writes.
2866 */
2867int ring_buffer_record_is_on(struct ring_buffer *buffer)
2868{
2869 return !atomic_read(&buffer->record_disabled);
2870}
2871
2872/**
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002873 * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
2874 * @buffer: The ring buffer to stop writes to.
2875 * @cpu: The CPU buffer to stop
2876 *
2877 * This prevents all writes to the buffer. Any attempt to write
2878 * to the buffer after this will fail and return NULL.
2879 *
2880 * The caller should call synchronize_sched() after this.
2881 */
2882void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
2883{
2884 struct ring_buffer_per_cpu *cpu_buffer;
2885
Rusty Russell9e01c1b2009-01-01 10:12:22 +10302886 if (!cpumask_test_cpu(cpu, buffer->cpumask))
Steven Rostedt8aabee52009-03-12 13:13:49 -04002887 return;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002888
2889 cpu_buffer = buffer->buffers[cpu];
2890 atomic_inc(&cpu_buffer->record_disabled);
2891}
Robert Richterc4f50182008-12-11 16:49:22 +01002892EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002893
2894/**
2895 * ring_buffer_record_enable_cpu - enable writes to the buffer
2896 * @buffer: The ring buffer to enable writes
2897 * @cpu: The CPU to enable.
2898 *
2899 * Note, multiple disables will need the same number of enables
Adam Buchbinderc41b20e2009-12-11 16:35:39 -05002900 * to truly enable the writing (much like preempt_disable).
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002901 */
2902void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
2903{
2904 struct ring_buffer_per_cpu *cpu_buffer;
2905
Rusty Russell9e01c1b2009-01-01 10:12:22 +10302906 if (!cpumask_test_cpu(cpu, buffer->cpumask))
Steven Rostedt8aabee52009-03-12 13:13:49 -04002907 return;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002908
2909 cpu_buffer = buffer->buffers[cpu];
2910 atomic_dec(&cpu_buffer->record_disabled);
2911}
Robert Richterc4f50182008-12-11 16:49:22 +01002912EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002913
Steven Rostedtf6195aa2010-09-01 12:23:12 -04002914/*
2915 * The total entries in the ring buffer is the running counter
2916 * of entries entered into the ring buffer, minus the sum of
2917 * the entries read from the ring buffer and the number of
2918 * entries that were overwritten.
2919 */
2920static inline unsigned long
2921rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
2922{
2923 return local_read(&cpu_buffer->entries) -
2924 (local_read(&cpu_buffer->overrun) + cpu_buffer->read);
2925}
2926
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002927/**
Vaibhav Nagarnaikc64e1482011-08-16 14:46:16 -07002928 * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
2929 * @buffer: The ring buffer
2930 * @cpu: The per CPU buffer to read from.
2931 */
2932unsigned long ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu)
2933{
2934 unsigned long flags;
2935 struct ring_buffer_per_cpu *cpu_buffer;
2936 struct buffer_page *bpage;
2937 unsigned long ret;
2938
2939 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2940 return 0;
2941
2942 cpu_buffer = buffer->buffers[cpu];
Linus Torvalds7115e3f2011-10-26 17:03:38 +02002943 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
Vaibhav Nagarnaikc64e1482011-08-16 14:46:16 -07002944 /*
2945 * if the tail is on reader_page, oldest time stamp is on the reader
2946 * page
2947 */
2948 if (cpu_buffer->tail_page == cpu_buffer->reader_page)
2949 bpage = cpu_buffer->reader_page;
2950 else
2951 bpage = rb_set_head_page(cpu_buffer);
2952 ret = bpage->page->time_stamp;
Linus Torvalds7115e3f2011-10-26 17:03:38 +02002953 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
Vaibhav Nagarnaikc64e1482011-08-16 14:46:16 -07002954
2955 return ret;
2956}
2957EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
2958
2959/**
2960 * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer
2961 * @buffer: The ring buffer
2962 * @cpu: The per CPU buffer to read from.
2963 */
2964unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu)
2965{
2966 struct ring_buffer_per_cpu *cpu_buffer;
2967 unsigned long ret;
2968
2969 if (!cpumask_test_cpu(cpu, buffer->cpumask))
2970 return 0;
2971
2972 cpu_buffer = buffer->buffers[cpu];
2973 ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
2974
2975 return ret;
2976}
2977EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
2978
2979/**
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002980 * ring_buffer_entries_cpu - get the number of entries in a cpu buffer
2981 * @buffer: The ring buffer
2982 * @cpu: The per CPU buffer to get the entries from.
2983 */
2984unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
2985{
2986 struct ring_buffer_per_cpu *cpu_buffer;
2987
Rusty Russell9e01c1b2009-01-01 10:12:22 +10302988 if (!cpumask_test_cpu(cpu, buffer->cpumask))
Steven Rostedt8aabee52009-03-12 13:13:49 -04002989 return 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002990
2991 cpu_buffer = buffer->buffers[cpu];
Steven Rostedt554f7862009-03-11 22:00:13 -04002992
Steven Rostedtf6195aa2010-09-01 12:23:12 -04002993 return rb_num_of_entries(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002994}
Robert Richterc4f50182008-12-11 16:49:22 +01002995EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04002996
2997/**
2998 * ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
2999 * @buffer: The ring buffer
3000 * @cpu: The per CPU buffer to get the number of overruns from
3001 */
3002unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
3003{
3004 struct ring_buffer_per_cpu *cpu_buffer;
Steven Rostedt8aabee52009-03-12 13:13:49 -04003005 unsigned long ret;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003006
Rusty Russell9e01c1b2009-01-01 10:12:22 +10303007 if (!cpumask_test_cpu(cpu, buffer->cpumask))
Steven Rostedt8aabee52009-03-12 13:13:49 -04003008 return 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003009
3010 cpu_buffer = buffer->buffers[cpu];
Steven Rostedt77ae3652009-03-27 11:00:29 -04003011 ret = local_read(&cpu_buffer->overrun);
Steven Rostedt554f7862009-03-11 22:00:13 -04003012
3013 return ret;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003014}
Robert Richterc4f50182008-12-11 16:49:22 +01003015EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003016
3017/**
Steven Rostedtf0d2c682009-04-29 13:43:37 -04003018 * ring_buffer_commit_overrun_cpu - get the number of overruns caused by commits
3019 * @buffer: The ring buffer
3020 * @cpu: The per CPU buffer to get the number of overruns from
3021 */
3022unsigned long
3023ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
3024{
3025 struct ring_buffer_per_cpu *cpu_buffer;
3026 unsigned long ret;
3027
3028 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3029 return 0;
3030
3031 cpu_buffer = buffer->buffers[cpu];
Steven Rostedt77ae3652009-03-27 11:00:29 -04003032 ret = local_read(&cpu_buffer->commit_overrun);
Steven Rostedtf0d2c682009-04-29 13:43:37 -04003033
3034 return ret;
3035}
3036EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
3037
3038/**
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003039 * ring_buffer_entries - get the number of entries in a buffer
3040 * @buffer: The ring buffer
3041 *
3042 * Returns the total number of entries in the ring buffer
3043 * (all CPU entries)
3044 */
3045unsigned long ring_buffer_entries(struct ring_buffer *buffer)
3046{
3047 struct ring_buffer_per_cpu *cpu_buffer;
3048 unsigned long entries = 0;
3049 int cpu;
3050
3051 /* if you care about this being correct, lock the buffer */
3052 for_each_buffer_cpu(buffer, cpu) {
3053 cpu_buffer = buffer->buffers[cpu];
Steven Rostedtf6195aa2010-09-01 12:23:12 -04003054 entries += rb_num_of_entries(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003055 }
3056
3057 return entries;
3058}
Robert Richterc4f50182008-12-11 16:49:22 +01003059EXPORT_SYMBOL_GPL(ring_buffer_entries);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003060
3061/**
Jiri Olsa67b394f2009-10-23 19:36:18 -04003062 * ring_buffer_overruns - get the number of overruns in buffer
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003063 * @buffer: The ring buffer
3064 *
3065 * Returns the total number of overruns in the ring buffer
3066 * (all CPU entries)
3067 */
3068unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
3069{
3070 struct ring_buffer_per_cpu *cpu_buffer;
3071 unsigned long overruns = 0;
3072 int cpu;
3073
3074 /* if you care about this being correct, lock the buffer */
3075 for_each_buffer_cpu(buffer, cpu) {
3076 cpu_buffer = buffer->buffers[cpu];
Steven Rostedt77ae3652009-03-27 11:00:29 -04003077 overruns += local_read(&cpu_buffer->overrun);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003078 }
3079
3080 return overruns;
3081}
Robert Richterc4f50182008-12-11 16:49:22 +01003082EXPORT_SYMBOL_GPL(ring_buffer_overruns);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003083
Steven Rostedt642edba2008-11-12 00:01:26 -05003084static void rb_iter_reset(struct ring_buffer_iter *iter)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003085{
3086 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3087
Steven Rostedtd7690412008-10-01 00:29:53 -04003088 /* Iterator usage is expected to have record disabled */
3089 if (list_empty(&cpu_buffer->reader_page->list)) {
Steven Rostedt77ae3652009-03-27 11:00:29 -04003090 iter->head_page = rb_set_head_page(cpu_buffer);
3091 if (unlikely(!iter->head_page))
3092 return;
3093 iter->head = iter->head_page->read;
Steven Rostedtd7690412008-10-01 00:29:53 -04003094 } else {
3095 iter->head_page = cpu_buffer->reader_page;
Steven Rostedt6f807ac2008-10-04 02:00:58 -04003096 iter->head = cpu_buffer->reader_page->read;
Steven Rostedtd7690412008-10-01 00:29:53 -04003097 }
3098 if (iter->head)
3099 iter->read_stamp = cpu_buffer->read_stamp;
3100 else
Steven Rostedtabc9b562008-12-02 15:34:06 -05003101 iter->read_stamp = iter->head_page->page->time_stamp;
Steven Rostedt492a74f2010-01-25 15:17:47 -05003102 iter->cache_reader_page = cpu_buffer->reader_page;
3103 iter->cache_read = cpu_buffer->read;
Steven Rostedt642edba2008-11-12 00:01:26 -05003104}
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003105
Steven Rostedt642edba2008-11-12 00:01:26 -05003106/**
3107 * ring_buffer_iter_reset - reset an iterator
3108 * @iter: The iterator to reset
3109 *
3110 * Resets the iterator, so that it will start from the beginning
3111 * again.
3112 */
3113void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
3114{
Steven Rostedt554f7862009-03-11 22:00:13 -04003115 struct ring_buffer_per_cpu *cpu_buffer;
Steven Rostedt642edba2008-11-12 00:01:26 -05003116 unsigned long flags;
3117
Steven Rostedt554f7862009-03-11 22:00:13 -04003118 if (!iter)
3119 return;
3120
3121 cpu_buffer = iter->cpu_buffer;
3122
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003123 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
Steven Rostedt642edba2008-11-12 00:01:26 -05003124 rb_iter_reset(iter);
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003125 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003126}
Robert Richterc4f50182008-12-11 16:49:22 +01003127EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003128
3129/**
3130 * ring_buffer_iter_empty - check if an iterator has no more to read
3131 * @iter: The iterator to check
3132 */
3133int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
3134{
3135 struct ring_buffer_per_cpu *cpu_buffer;
3136
3137 cpu_buffer = iter->cpu_buffer;
3138
Steven Rostedtbf41a152008-10-04 02:00:59 -04003139 return iter->head_page == cpu_buffer->commit_page &&
3140 iter->head == rb_commit_index(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003141}
Robert Richterc4f50182008-12-11 16:49:22 +01003142EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003143
3144static void
3145rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
3146 struct ring_buffer_event *event)
3147{
3148 u64 delta;
3149
Lai Jiangshan334d4162009-04-24 11:27:05 +08003150 switch (event->type_len) {
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003151 case RINGBUF_TYPE_PADDING:
3152 return;
3153
3154 case RINGBUF_TYPE_TIME_EXTEND:
3155 delta = event->array[0];
3156 delta <<= TS_SHIFT;
3157 delta += event->time_delta;
3158 cpu_buffer->read_stamp += delta;
3159 return;
3160
3161 case RINGBUF_TYPE_TIME_STAMP:
3162 /* FIXME: not implemented */
3163 return;
3164
3165 case RINGBUF_TYPE_DATA:
3166 cpu_buffer->read_stamp += event->time_delta;
3167 return;
3168
3169 default:
3170 BUG();
3171 }
3172 return;
3173}
3174
3175static void
3176rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
3177 struct ring_buffer_event *event)
3178{
3179 u64 delta;
3180
Lai Jiangshan334d4162009-04-24 11:27:05 +08003181 switch (event->type_len) {
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003182 case RINGBUF_TYPE_PADDING:
3183 return;
3184
3185 case RINGBUF_TYPE_TIME_EXTEND:
3186 delta = event->array[0];
3187 delta <<= TS_SHIFT;
3188 delta += event->time_delta;
3189 iter->read_stamp += delta;
3190 return;
3191
3192 case RINGBUF_TYPE_TIME_STAMP:
3193 /* FIXME: not implemented */
3194 return;
3195
3196 case RINGBUF_TYPE_DATA:
3197 iter->read_stamp += event->time_delta;
3198 return;
3199
3200 default:
3201 BUG();
3202 }
3203 return;
3204}
3205
Steven Rostedtd7690412008-10-01 00:29:53 -04003206static struct buffer_page *
3207rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003208{
Steven Rostedtd7690412008-10-01 00:29:53 -04003209 struct buffer_page *reader = NULL;
Steven Rostedt66a8cb92010-03-31 13:21:56 -04003210 unsigned long overwrite;
Steven Rostedtd7690412008-10-01 00:29:53 -04003211 unsigned long flags;
Steven Rostedt818e3dd2008-10-31 09:58:35 -04003212 int nr_loops = 0;
Steven Rostedt77ae3652009-03-27 11:00:29 -04003213 int ret;
Steven Rostedtd7690412008-10-01 00:29:53 -04003214
Steven Rostedt3e03fb72008-11-06 00:09:43 -05003215 local_irq_save(flags);
Thomas Gleixner0199c4e2009-12-02 20:01:25 +01003216 arch_spin_lock(&cpu_buffer->lock);
Steven Rostedtd7690412008-10-01 00:29:53 -04003217
3218 again:
Steven Rostedt818e3dd2008-10-31 09:58:35 -04003219 /*
3220 * This should normally only loop twice. But because the
3221 * start of the reader inserts an empty page, it causes
3222 * a case where we will loop three times. There should be no
3223 * reason to loop four times (that I know of).
3224 */
Steven Rostedt3e89c7b2008-11-11 15:28:41 -05003225 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
Steven Rostedt818e3dd2008-10-31 09:58:35 -04003226 reader = NULL;
3227 goto out;
3228 }
3229
Steven Rostedtd7690412008-10-01 00:29:53 -04003230 reader = cpu_buffer->reader_page;
3231
3232 /* If there's more to read, return this page */
Steven Rostedtbf41a152008-10-04 02:00:59 -04003233 if (cpu_buffer->reader_page->read < rb_page_size(reader))
Steven Rostedtd7690412008-10-01 00:29:53 -04003234 goto out;
3235
3236 /* Never should we have an index greater than the size */
Steven Rostedt3e89c7b2008-11-11 15:28:41 -05003237 if (RB_WARN_ON(cpu_buffer,
3238 cpu_buffer->reader_page->read > rb_page_size(reader)))
3239 goto out;
Steven Rostedtd7690412008-10-01 00:29:53 -04003240
3241 /* check if we caught up to the tail */
3242 reader = NULL;
Steven Rostedtbf41a152008-10-04 02:00:59 -04003243 if (cpu_buffer->commit_page == cpu_buffer->reader_page)
Steven Rostedtd7690412008-10-01 00:29:53 -04003244 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003245
Steven Rostedta5fb8332012-06-28 13:35:04 -04003246 /* Don't bother swapping if the ring buffer is empty */
3247 if (rb_num_of_entries(cpu_buffer) == 0)
3248 goto out;
3249
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003250 /*
Steven Rostedtd7690412008-10-01 00:29:53 -04003251 * Reset the reader page to size zero.
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003252 */
Steven Rostedt77ae3652009-03-27 11:00:29 -04003253 local_set(&cpu_buffer->reader_page->write, 0);
3254 local_set(&cpu_buffer->reader_page->entries, 0);
3255 local_set(&cpu_buffer->reader_page->page->commit, 0);
Steven Rostedtff0ff842010-03-31 22:11:42 -04003256 cpu_buffer->reader_page->real_end = 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003257
Steven Rostedt77ae3652009-03-27 11:00:29 -04003258 spin:
3259 /*
3260 * Splice the empty reader page into the list around the head.
3261 */
3262 reader = rb_set_head_page(cpu_buffer);
Steven Rostedt0e1ff5d2010-01-06 20:40:44 -05003263 cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
Steven Rostedtd7690412008-10-01 00:29:53 -04003264 cpu_buffer->reader_page->list.prev = reader->list.prev;
Steven Rostedtbf41a152008-10-04 02:00:59 -04003265
Steven Rostedt3adc54f2009-03-30 15:32:01 -04003266 /*
3267 * cpu_buffer->pages just needs to point to the buffer, it
3268 * has no specific buffer page to point to. Lets move it out
Lucas De Marchi25985ed2011-03-30 22:57:33 -03003269 * of our way so we don't accidentally swap it.
Steven Rostedt3adc54f2009-03-30 15:32:01 -04003270 */
3271 cpu_buffer->pages = reader->list.prev;
3272
Steven Rostedt77ae3652009-03-27 11:00:29 -04003273 /* The reader page will be pointing to the new head */
3274 rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
Steven Rostedtd7690412008-10-01 00:29:53 -04003275
3276 /*
Steven Rostedt66a8cb92010-03-31 13:21:56 -04003277 * We want to make sure we read the overruns after we set up our
3278 * pointers to the next object. The writer side does a
3279 * cmpxchg to cross pages which acts as the mb on the writer
3280 * side. Note, the reader will constantly fail the swap
3281 * while the writer is updating the pointers, so this
3282 * guarantees that the overwrite recorded here is the one we
3283 * want to compare with the last_overrun.
3284 */
3285 smp_mb();
3286 overwrite = local_read(&(cpu_buffer->overrun));
3287
3288 /*
Steven Rostedt77ae3652009-03-27 11:00:29 -04003289 * Here's the tricky part.
3290 *
3291 * We need to move the pointer past the header page.
3292 * But we can only do that if a writer is not currently
3293 * moving it. The page before the header page has the
3294 * flag bit '1' set if it is pointing to the page we want.
3295 * but if the writer is in the process of moving it
3296 * than it will be '2' or already moved '0'.
Steven Rostedtd7690412008-10-01 00:29:53 -04003297 */
Steven Rostedtd7690412008-10-01 00:29:53 -04003298
Steven Rostedt77ae3652009-03-27 11:00:29 -04003299 ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
3300
3301 /*
3302 * If we did not convert it, then we must try again.
3303 */
3304 if (!ret)
3305 goto spin;
3306
3307 /*
3308 * Yeah! We succeeded in replacing the page.
3309 *
3310 * Now make the new head point back to the reader page.
3311 */
David Sharp5ded3dc62010-01-06 17:12:07 -08003312 rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
Steven Rostedt77ae3652009-03-27 11:00:29 -04003313 rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
Steven Rostedtd7690412008-10-01 00:29:53 -04003314
3315 /* Finally update the reader page to the new head */
3316 cpu_buffer->reader_page = reader;
3317 rb_reset_reader_page(cpu_buffer);
3318
Steven Rostedt66a8cb92010-03-31 13:21:56 -04003319 if (overwrite != cpu_buffer->last_overrun) {
3320 cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
3321 cpu_buffer->last_overrun = overwrite;
3322 }
3323
Steven Rostedtd7690412008-10-01 00:29:53 -04003324 goto again;
3325
3326 out:
Thomas Gleixner0199c4e2009-12-02 20:01:25 +01003327 arch_spin_unlock(&cpu_buffer->lock);
Steven Rostedt3e03fb72008-11-06 00:09:43 -05003328 local_irq_restore(flags);
Steven Rostedtd7690412008-10-01 00:29:53 -04003329
3330 return reader;
3331}
3332
3333static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
3334{
3335 struct ring_buffer_event *event;
3336 struct buffer_page *reader;
3337 unsigned length;
3338
3339 reader = rb_get_reader_page(cpu_buffer);
3340
3341 /* This function should not be called when buffer is empty */
Steven Rostedt3e89c7b2008-11-11 15:28:41 -05003342 if (RB_WARN_ON(cpu_buffer, !reader))
3343 return;
Steven Rostedtd7690412008-10-01 00:29:53 -04003344
3345 event = rb_reader_event(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003346
Steven Rostedta1863c22009-09-03 10:23:58 -04003347 if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
Steven Rostedte4906ef2009-04-30 20:49:44 -04003348 cpu_buffer->read++;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003349
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003350 rb_update_read_stamp(cpu_buffer, event);
3351
Steven Rostedtd7690412008-10-01 00:29:53 -04003352 length = rb_event_length(event);
Steven Rostedt6f807ac2008-10-04 02:00:58 -04003353 cpu_buffer->reader_page->read += length;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003354}
3355
3356static void rb_advance_iter(struct ring_buffer_iter *iter)
3357{
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003358 struct ring_buffer_per_cpu *cpu_buffer;
3359 struct ring_buffer_event *event;
3360 unsigned length;
3361
3362 cpu_buffer = iter->cpu_buffer;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003363
3364 /*
3365 * Check if we are at the end of the buffer.
3366 */
Steven Rostedtbf41a152008-10-04 02:00:59 -04003367 if (iter->head >= rb_page_size(iter->head_page)) {
Steven Rostedtea05b572009-06-03 09:30:10 -04003368 /* discarded commits can make the page empty */
3369 if (iter->head_page == cpu_buffer->commit_page)
Steven Rostedt3e89c7b2008-11-11 15:28:41 -05003370 return;
Steven Rostedtd7690412008-10-01 00:29:53 -04003371 rb_inc_iter(iter);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003372 return;
3373 }
3374
3375 event = rb_iter_head_event(iter);
3376
3377 length = rb_event_length(event);
3378
3379 /*
3380 * This should not be called to advance the header if we are
3381 * at the tail of the buffer.
3382 */
Steven Rostedt3e89c7b2008-11-11 15:28:41 -05003383 if (RB_WARN_ON(cpu_buffer,
Steven Rostedtf536aaf2008-11-10 23:07:30 -05003384 (iter->head_page == cpu_buffer->commit_page) &&
Steven Rostedt3e89c7b2008-11-11 15:28:41 -05003385 (iter->head + length > rb_commit_index(cpu_buffer))))
3386 return;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003387
3388 rb_update_iter_read_stamp(iter, event);
3389
3390 iter->head += length;
3391
3392 /* check for end of page padding */
Steven Rostedtbf41a152008-10-04 02:00:59 -04003393 if ((iter->head >= rb_page_size(iter->head_page)) &&
3394 (iter->head_page != cpu_buffer->commit_page))
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003395 rb_advance_iter(iter);
3396}
3397
Steven Rostedt66a8cb92010-03-31 13:21:56 -04003398static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
3399{
3400 return cpu_buffer->lost_events;
3401}
3402
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003403static struct ring_buffer_event *
Steven Rostedt66a8cb92010-03-31 13:21:56 -04003404rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
3405 unsigned long *lost_events)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003406{
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003407 struct ring_buffer_event *event;
Steven Rostedtd7690412008-10-01 00:29:53 -04003408 struct buffer_page *reader;
Steven Rostedt818e3dd2008-10-31 09:58:35 -04003409 int nr_loops = 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003410
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003411 again:
Steven Rostedt818e3dd2008-10-31 09:58:35 -04003412 /*
Steven Rostedt69d1b832010-10-07 18:18:05 -04003413 * We repeat when a time extend is encountered.
3414 * Since the time extend is always attached to a data event,
3415 * we should never loop more than once.
3416 * (We never hit the following condition more than twice).
Steven Rostedt818e3dd2008-10-31 09:58:35 -04003417 */
Steven Rostedt69d1b832010-10-07 18:18:05 -04003418 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
Steven Rostedt818e3dd2008-10-31 09:58:35 -04003419 return NULL;
Steven Rostedt818e3dd2008-10-31 09:58:35 -04003420
Steven Rostedtd7690412008-10-01 00:29:53 -04003421 reader = rb_get_reader_page(cpu_buffer);
3422 if (!reader)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003423 return NULL;
3424
Steven Rostedtd7690412008-10-01 00:29:53 -04003425 event = rb_reader_event(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003426
Lai Jiangshan334d4162009-04-24 11:27:05 +08003427 switch (event->type_len) {
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003428 case RINGBUF_TYPE_PADDING:
Tom Zanussi2d622712009-03-22 03:30:49 -05003429 if (rb_null_event(event))
3430 RB_WARN_ON(cpu_buffer, 1);
3431 /*
3432 * Because the writer could be discarding every
3433 * event it creates (which would probably be bad)
3434 * if we were to go back to "again" then we may never
3435 * catch up, and will trigger the warn on, or lock
3436 * the box. Return the padding, and we will release
3437 * the current locks, and try again.
3438 */
Tom Zanussi2d622712009-03-22 03:30:49 -05003439 return event;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003440
3441 case RINGBUF_TYPE_TIME_EXTEND:
3442 /* Internal data, OK to advance */
Steven Rostedtd7690412008-10-01 00:29:53 -04003443 rb_advance_reader(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003444 goto again;
3445
3446 case RINGBUF_TYPE_TIME_STAMP:
3447 /* FIXME: not implemented */
Steven Rostedtd7690412008-10-01 00:29:53 -04003448 rb_advance_reader(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003449 goto again;
3450
3451 case RINGBUF_TYPE_DATA:
3452 if (ts) {
3453 *ts = cpu_buffer->read_stamp + event->time_delta;
Robert Richterd8eeb2d2009-07-31 14:58:04 +02003454 ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
Steven Rostedt37886f62009-03-17 17:22:06 -04003455 cpu_buffer->cpu, ts);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003456 }
Steven Rostedt66a8cb92010-03-31 13:21:56 -04003457 if (lost_events)
3458 *lost_events = rb_lost_events(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003459 return event;
3460
3461 default:
3462 BUG();
3463 }
3464
3465 return NULL;
3466}
Robert Richterc4f50182008-12-11 16:49:22 +01003467EXPORT_SYMBOL_GPL(ring_buffer_peek);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003468
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003469static struct ring_buffer_event *
3470rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003471{
3472 struct ring_buffer *buffer;
3473 struct ring_buffer_per_cpu *cpu_buffer;
3474 struct ring_buffer_event *event;
Steven Rostedt818e3dd2008-10-31 09:58:35 -04003475 int nr_loops = 0;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003476
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003477 cpu_buffer = iter->cpu_buffer;
3478 buffer = cpu_buffer->buffer;
3479
Steven Rostedt492a74f2010-01-25 15:17:47 -05003480 /*
3481 * Check if someone performed a consuming read to
3482 * the buffer. A consuming read invalidates the iterator
3483 * and we need to reset the iterator in this case.
3484 */
3485 if (unlikely(iter->cache_read != cpu_buffer->read ||
3486 iter->cache_reader_page != cpu_buffer->reader_page))
3487 rb_iter_reset(iter);
3488
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003489 again:
Steven Rostedt3c05d742010-01-26 16:14:08 -05003490 if (ring_buffer_iter_empty(iter))
3491 return NULL;
3492
Steven Rostedt818e3dd2008-10-31 09:58:35 -04003493 /*
Steven Rostedt69d1b832010-10-07 18:18:05 -04003494 * We repeat when a time extend is encountered.
3495 * Since the time extend is always attached to a data event,
3496 * we should never loop more than once.
3497 * (We never hit the following condition more than twice).
Steven Rostedt818e3dd2008-10-31 09:58:35 -04003498 */
Steven Rostedt69d1b832010-10-07 18:18:05 -04003499 if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
Steven Rostedt818e3dd2008-10-31 09:58:35 -04003500 return NULL;
Steven Rostedt818e3dd2008-10-31 09:58:35 -04003501
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003502 if (rb_per_cpu_empty(cpu_buffer))
3503 return NULL;
3504
Steven Rostedt3c05d742010-01-26 16:14:08 -05003505 if (iter->head >= local_read(&iter->head_page->page->commit)) {
3506 rb_inc_iter(iter);
3507 goto again;
3508 }
3509
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003510 event = rb_iter_head_event(iter);
3511
Lai Jiangshan334d4162009-04-24 11:27:05 +08003512 switch (event->type_len) {
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003513 case RINGBUF_TYPE_PADDING:
Tom Zanussi2d622712009-03-22 03:30:49 -05003514 if (rb_null_event(event)) {
3515 rb_inc_iter(iter);
3516 goto again;
3517 }
3518 rb_advance_iter(iter);
3519 return event;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003520
3521 case RINGBUF_TYPE_TIME_EXTEND:
3522 /* Internal data, OK to advance */
3523 rb_advance_iter(iter);
3524 goto again;
3525
3526 case RINGBUF_TYPE_TIME_STAMP:
3527 /* FIXME: not implemented */
3528 rb_advance_iter(iter);
3529 goto again;
3530
3531 case RINGBUF_TYPE_DATA:
3532 if (ts) {
3533 *ts = iter->read_stamp + event->time_delta;
Steven Rostedt37886f62009-03-17 17:22:06 -04003534 ring_buffer_normalize_time_stamp(buffer,
3535 cpu_buffer->cpu, ts);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003536 }
3537 return event;
3538
3539 default:
3540 BUG();
3541 }
3542
3543 return NULL;
3544}
Robert Richterc4f50182008-12-11 16:49:22 +01003545EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003546
Steven Rostedt8d707e82009-06-16 21:22:48 -04003547static inline int rb_ok_to_lock(void)
3548{
3549 /*
3550 * If an NMI die dumps out the content of the ring buffer
3551 * do not grab locks. We also permanently disable the ring
3552 * buffer too. A one time deal is all you get from reading
3553 * the ring buffer from an NMI.
3554 */
Steven Rostedt464e85e2009-08-05 15:26:37 -04003555 if (likely(!in_nmi()))
Steven Rostedt8d707e82009-06-16 21:22:48 -04003556 return 1;
3557
3558 tracing_off_permanent();
3559 return 0;
3560}
3561
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003562/**
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003563 * ring_buffer_peek - peek at the next event to be read
3564 * @buffer: The ring buffer to read
3565 * @cpu: The cpu to peak at
3566 * @ts: The timestamp counter of this event.
Steven Rostedt66a8cb92010-03-31 13:21:56 -04003567 * @lost_events: a variable to store if events were lost (may be NULL)
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003568 *
3569 * This will return the event that will be read next, but does
3570 * not consume the data.
3571 */
3572struct ring_buffer_event *
Steven Rostedt66a8cb92010-03-31 13:21:56 -04003573ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
3574 unsigned long *lost_events)
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003575{
3576 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
Steven Rostedt8aabee52009-03-12 13:13:49 -04003577 struct ring_buffer_event *event;
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003578 unsigned long flags;
Steven Rostedt8d707e82009-06-16 21:22:48 -04003579 int dolock;
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003580
Steven Rostedt554f7862009-03-11 22:00:13 -04003581 if (!cpumask_test_cpu(cpu, buffer->cpumask))
Steven Rostedt8aabee52009-03-12 13:13:49 -04003582 return NULL;
Steven Rostedt554f7862009-03-11 22:00:13 -04003583
Steven Rostedt8d707e82009-06-16 21:22:48 -04003584 dolock = rb_ok_to_lock();
Tom Zanussi2d622712009-03-22 03:30:49 -05003585 again:
Steven Rostedt8d707e82009-06-16 21:22:48 -04003586 local_irq_save(flags);
3587 if (dolock)
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003588 raw_spin_lock(&cpu_buffer->reader_lock);
Steven Rostedt66a8cb92010-03-31 13:21:56 -04003589 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
Robert Richter469535a2009-07-30 19:19:18 +02003590 if (event && event->type_len == RINGBUF_TYPE_PADDING)
3591 rb_advance_reader(cpu_buffer);
Steven Rostedt8d707e82009-06-16 21:22:48 -04003592 if (dolock)
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003593 raw_spin_unlock(&cpu_buffer->reader_lock);
Steven Rostedt8d707e82009-06-16 21:22:48 -04003594 local_irq_restore(flags);
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003595
Steven Rostedt1b959e12009-09-03 10:12:13 -04003596 if (event && event->type_len == RINGBUF_TYPE_PADDING)
Tom Zanussi2d622712009-03-22 03:30:49 -05003597 goto again;
Tom Zanussi2d622712009-03-22 03:30:49 -05003598
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003599 return event;
3600}
3601
3602/**
3603 * ring_buffer_iter_peek - peek at the next event to be read
3604 * @iter: The ring buffer iterator
3605 * @ts: The timestamp counter of this event.
3606 *
3607 * This will return the event that will be read next, but does
3608 * not increment the iterator.
3609 */
3610struct ring_buffer_event *
3611ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
3612{
3613 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3614 struct ring_buffer_event *event;
3615 unsigned long flags;
3616
Tom Zanussi2d622712009-03-22 03:30:49 -05003617 again:
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003618 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003619 event = rb_iter_peek(iter, ts);
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003620 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003621
Steven Rostedt1b959e12009-09-03 10:12:13 -04003622 if (event && event->type_len == RINGBUF_TYPE_PADDING)
Tom Zanussi2d622712009-03-22 03:30:49 -05003623 goto again;
Tom Zanussi2d622712009-03-22 03:30:49 -05003624
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003625 return event;
3626}
3627
3628/**
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003629 * ring_buffer_consume - return an event and consume it
3630 * @buffer: The ring buffer to get the next event from
Steven Rostedt66a8cb92010-03-31 13:21:56 -04003631 * @cpu: the cpu to read the buffer from
3632 * @ts: a variable to store the timestamp (may be NULL)
3633 * @lost_events: a variable to store if events were lost (may be NULL)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003634 *
3635 * Returns the next event in the ring buffer, and that event is consumed.
3636 * Meaning, that sequential reads will keep returning a different event,
3637 * and eventually empty the ring buffer if the producer is slower.
3638 */
3639struct ring_buffer_event *
Steven Rostedt66a8cb92010-03-31 13:21:56 -04003640ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts,
3641 unsigned long *lost_events)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003642{
Steven Rostedt554f7862009-03-11 22:00:13 -04003643 struct ring_buffer_per_cpu *cpu_buffer;
3644 struct ring_buffer_event *event = NULL;
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003645 unsigned long flags;
Steven Rostedt8d707e82009-06-16 21:22:48 -04003646 int dolock;
3647
3648 dolock = rb_ok_to_lock();
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003649
Tom Zanussi2d622712009-03-22 03:30:49 -05003650 again:
Steven Rostedt554f7862009-03-11 22:00:13 -04003651 /* might be called in atomic */
3652 preempt_disable();
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003653
Steven Rostedt554f7862009-03-11 22:00:13 -04003654 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3655 goto out;
3656
3657 cpu_buffer = buffer->buffers[cpu];
Steven Rostedt8d707e82009-06-16 21:22:48 -04003658 local_irq_save(flags);
3659 if (dolock)
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003660 raw_spin_lock(&cpu_buffer->reader_lock);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003661
Steven Rostedt66a8cb92010-03-31 13:21:56 -04003662 event = rb_buffer_peek(cpu_buffer, ts, lost_events);
3663 if (event) {
3664 cpu_buffer->lost_events = 0;
Robert Richter469535a2009-07-30 19:19:18 +02003665 rb_advance_reader(cpu_buffer);
Steven Rostedt66a8cb92010-03-31 13:21:56 -04003666 }
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003667
Steven Rostedt8d707e82009-06-16 21:22:48 -04003668 if (dolock)
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003669 raw_spin_unlock(&cpu_buffer->reader_lock);
Steven Rostedt8d707e82009-06-16 21:22:48 -04003670 local_irq_restore(flags);
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003671
Steven Rostedt554f7862009-03-11 22:00:13 -04003672 out:
3673 preempt_enable();
3674
Steven Rostedt1b959e12009-09-03 10:12:13 -04003675 if (event && event->type_len == RINGBUF_TYPE_PADDING)
Tom Zanussi2d622712009-03-22 03:30:49 -05003676 goto again;
Tom Zanussi2d622712009-03-22 03:30:49 -05003677
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003678 return event;
3679}
Robert Richterc4f50182008-12-11 16:49:22 +01003680EXPORT_SYMBOL_GPL(ring_buffer_consume);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003681
3682/**
David Miller72c9ddf2010-04-20 15:47:11 -07003683 * ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003684 * @buffer: The ring buffer to read from
3685 * @cpu: The cpu buffer to iterate over
3686 *
David Miller72c9ddf2010-04-20 15:47:11 -07003687 * This performs the initial preparations necessary to iterate
3688 * through the buffer. Memory is allocated, buffer recording
3689 * is disabled, and the iterator pointer is returned to the caller.
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003690 *
David Miller72c9ddf2010-04-20 15:47:11 -07003691 * Disabling buffer recordng prevents the reading from being
3692 * corrupted. This is not a consuming read, so a producer is not
3693 * expected.
3694 *
3695 * After a sequence of ring_buffer_read_prepare calls, the user is
3696 * expected to make at least one call to ring_buffer_prepare_sync.
3697 * Afterwards, ring_buffer_read_start is invoked to get things going
3698 * for real.
3699 *
3700 * This overall must be paired with ring_buffer_finish.
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003701 */
3702struct ring_buffer_iter *
David Miller72c9ddf2010-04-20 15:47:11 -07003703ring_buffer_read_prepare(struct ring_buffer *buffer, int cpu)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003704{
3705 struct ring_buffer_per_cpu *cpu_buffer;
Steven Rostedt8aabee52009-03-12 13:13:49 -04003706 struct ring_buffer_iter *iter;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003707
Rusty Russell9e01c1b2009-01-01 10:12:22 +10303708 if (!cpumask_test_cpu(cpu, buffer->cpumask))
Steven Rostedt8aabee52009-03-12 13:13:49 -04003709 return NULL;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003710
3711 iter = kmalloc(sizeof(*iter), GFP_KERNEL);
3712 if (!iter)
Steven Rostedt8aabee52009-03-12 13:13:49 -04003713 return NULL;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003714
3715 cpu_buffer = buffer->buffers[cpu];
3716
3717 iter->cpu_buffer = cpu_buffer;
3718
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07003719 atomic_inc(&buffer->resize_disabled);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003720 atomic_inc(&cpu_buffer->record_disabled);
David Miller72c9ddf2010-04-20 15:47:11 -07003721
3722 return iter;
3723}
3724EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
3725
3726/**
3727 * ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
3728 *
3729 * All previously invoked ring_buffer_read_prepare calls to prepare
3730 * iterators will be synchronized. Afterwards, read_buffer_read_start
3731 * calls on those iterators are allowed.
3732 */
3733void
3734ring_buffer_read_prepare_sync(void)
3735{
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003736 synchronize_sched();
David Miller72c9ddf2010-04-20 15:47:11 -07003737}
3738EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
3739
3740/**
3741 * ring_buffer_read_start - start a non consuming read of the buffer
3742 * @iter: The iterator returned by ring_buffer_read_prepare
3743 *
3744 * This finalizes the startup of an iteration through the buffer.
3745 * The iterator comes from a call to ring_buffer_read_prepare and
3746 * an intervening ring_buffer_read_prepare_sync must have been
3747 * performed.
3748 *
3749 * Must be paired with ring_buffer_finish.
3750 */
3751void
3752ring_buffer_read_start(struct ring_buffer_iter *iter)
3753{
3754 struct ring_buffer_per_cpu *cpu_buffer;
3755 unsigned long flags;
3756
3757 if (!iter)
3758 return;
3759
3760 cpu_buffer = iter->cpu_buffer;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003761
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003762 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
Thomas Gleixner0199c4e2009-12-02 20:01:25 +01003763 arch_spin_lock(&cpu_buffer->lock);
Steven Rostedt642edba2008-11-12 00:01:26 -05003764 rb_iter_reset(iter);
Thomas Gleixner0199c4e2009-12-02 20:01:25 +01003765 arch_spin_unlock(&cpu_buffer->lock);
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003766 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003767}
Robert Richterc4f50182008-12-11 16:49:22 +01003768EXPORT_SYMBOL_GPL(ring_buffer_read_start);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003769
3770/**
3771 * ring_buffer_finish - finish reading the iterator of the buffer
3772 * @iter: The iterator retrieved by ring_buffer_start
3773 *
3774 * This re-enables the recording to the buffer, and frees the
3775 * iterator.
3776 */
3777void
3778ring_buffer_read_finish(struct ring_buffer_iter *iter)
3779{
3780 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3781
Steven Rostedt659f4512012-05-14 17:02:33 -04003782 /*
3783 * Ring buffer is disabled from recording, here's a good place
3784 * to check the integrity of the ring buffer.
3785 */
3786 rb_check_pages(cpu_buffer);
3787
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003788 atomic_dec(&cpu_buffer->record_disabled);
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07003789 atomic_dec(&cpu_buffer->buffer->resize_disabled);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003790 kfree(iter);
3791}
Robert Richterc4f50182008-12-11 16:49:22 +01003792EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003793
3794/**
3795 * ring_buffer_read - read the next item in the ring buffer by the iterator
3796 * @iter: The ring buffer iterator
3797 * @ts: The time stamp of the event read.
3798 *
3799 * This reads the next event in the ring buffer and increments the iterator.
3800 */
3801struct ring_buffer_event *
3802ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
3803{
3804 struct ring_buffer_event *event;
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003805 struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
3806 unsigned long flags;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003807
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003808 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
Steven Rostedt7e9391c2009-09-03 10:02:09 -04003809 again:
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003810 event = rb_iter_peek(iter, ts);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003811 if (!event)
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003812 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003813
Steven Rostedt7e9391c2009-09-03 10:02:09 -04003814 if (event->type_len == RINGBUF_TYPE_PADDING)
3815 goto again;
3816
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003817 rb_advance_iter(iter);
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003818 out:
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003819 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003820
3821 return event;
3822}
Robert Richterc4f50182008-12-11 16:49:22 +01003823EXPORT_SYMBOL_GPL(ring_buffer_read);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003824
3825/**
3826 * ring_buffer_size - return the size of the ring buffer (in bytes)
3827 * @buffer: The ring buffer.
3828 */
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08003829unsigned long ring_buffer_size(struct ring_buffer *buffer, int cpu)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003830{
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08003831 /*
3832 * Earlier, this method returned
3833 * BUF_PAGE_SIZE * buffer->nr_pages
3834 * Since the nr_pages field is now removed, we have converted this to
3835 * return the per cpu buffer value.
3836 */
3837 if (!cpumask_test_cpu(cpu, buffer->cpumask))
3838 return 0;
3839
3840 return BUF_PAGE_SIZE * buffer->buffers[cpu]->nr_pages;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003841}
Robert Richterc4f50182008-12-11 16:49:22 +01003842EXPORT_SYMBOL_GPL(ring_buffer_size);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003843
3844static void
3845rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
3846{
Steven Rostedt77ae3652009-03-27 11:00:29 -04003847 rb_head_page_deactivate(cpu_buffer);
3848
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003849 cpu_buffer->head_page
Steven Rostedt3adc54f2009-03-30 15:32:01 -04003850 = list_entry(cpu_buffer->pages, struct buffer_page, list);
Steven Rostedtbf41a152008-10-04 02:00:59 -04003851 local_set(&cpu_buffer->head_page->write, 0);
Steven Rostedt778c55d2009-05-01 18:44:45 -04003852 local_set(&cpu_buffer->head_page->entries, 0);
Steven Rostedtabc9b562008-12-02 15:34:06 -05003853 local_set(&cpu_buffer->head_page->page->commit, 0);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003854
Steven Rostedt6f807ac2008-10-04 02:00:58 -04003855 cpu_buffer->head_page->read = 0;
Steven Rostedtbf41a152008-10-04 02:00:59 -04003856
3857 cpu_buffer->tail_page = cpu_buffer->head_page;
3858 cpu_buffer->commit_page = cpu_buffer->head_page;
3859
3860 INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
Vaibhav Nagarnaik5040b4b2012-05-03 18:59:51 -07003861 INIT_LIST_HEAD(&cpu_buffer->new_pages);
Steven Rostedtbf41a152008-10-04 02:00:59 -04003862 local_set(&cpu_buffer->reader_page->write, 0);
Steven Rostedt778c55d2009-05-01 18:44:45 -04003863 local_set(&cpu_buffer->reader_page->entries, 0);
Steven Rostedtabc9b562008-12-02 15:34:06 -05003864 local_set(&cpu_buffer->reader_page->page->commit, 0);
Steven Rostedt6f807ac2008-10-04 02:00:58 -04003865 cpu_buffer->reader_page->read = 0;
Steven Rostedtd7690412008-10-01 00:29:53 -04003866
Steven Rostedt77ae3652009-03-27 11:00:29 -04003867 local_set(&cpu_buffer->commit_overrun, 0);
Vaibhav Nagarnaikc64e1482011-08-16 14:46:16 -07003868 local_set(&cpu_buffer->entries_bytes, 0);
Steven Rostedt77ae3652009-03-27 11:00:29 -04003869 local_set(&cpu_buffer->overrun, 0);
Steven Rostedte4906ef2009-04-30 20:49:44 -04003870 local_set(&cpu_buffer->entries, 0);
Steven Rostedtfa743952009-06-16 12:37:57 -04003871 local_set(&cpu_buffer->committing, 0);
3872 local_set(&cpu_buffer->commits, 0);
Steven Rostedt77ae3652009-03-27 11:00:29 -04003873 cpu_buffer->read = 0;
Vaibhav Nagarnaikc64e1482011-08-16 14:46:16 -07003874 cpu_buffer->read_bytes = 0;
Steven Rostedt69507c02009-01-21 18:45:57 -05003875
3876 cpu_buffer->write_stamp = 0;
3877 cpu_buffer->read_stamp = 0;
Steven Rostedt77ae3652009-03-27 11:00:29 -04003878
Steven Rostedt66a8cb92010-03-31 13:21:56 -04003879 cpu_buffer->lost_events = 0;
3880 cpu_buffer->last_overrun = 0;
3881
Steven Rostedt77ae3652009-03-27 11:00:29 -04003882 rb_head_page_activate(cpu_buffer);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003883}
3884
3885/**
3886 * ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
3887 * @buffer: The ring buffer to reset a per cpu buffer of
3888 * @cpu: The CPU buffer to be reset
3889 */
3890void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
3891{
3892 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
3893 unsigned long flags;
3894
Rusty Russell9e01c1b2009-01-01 10:12:22 +10303895 if (!cpumask_test_cpu(cpu, buffer->cpumask))
Steven Rostedt8aabee52009-03-12 13:13:49 -04003896 return;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003897
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07003898 atomic_inc(&buffer->resize_disabled);
Steven Rostedt41ede232009-05-01 20:26:54 -04003899 atomic_inc(&cpu_buffer->record_disabled);
3900
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07003901 /* Make sure all commits have finished */
3902 synchronize_sched();
3903
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003904 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003905
Steven Rostedt41b6a952009-09-02 09:59:48 -04003906 if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
3907 goto out;
3908
Thomas Gleixner0199c4e2009-12-02 20:01:25 +01003909 arch_spin_lock(&cpu_buffer->lock);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003910
3911 rb_reset_cpu(cpu_buffer);
3912
Thomas Gleixner0199c4e2009-12-02 20:01:25 +01003913 arch_spin_unlock(&cpu_buffer->lock);
Steven Rostedtf83c9d02008-11-11 18:47:44 +01003914
Steven Rostedt41b6a952009-09-02 09:59:48 -04003915 out:
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003916 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
Steven Rostedt41ede232009-05-01 20:26:54 -04003917
3918 atomic_dec(&cpu_buffer->record_disabled);
Vaibhav Nagarnaik83f40312012-05-03 18:59:50 -07003919 atomic_dec(&buffer->resize_disabled);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003920}
Robert Richterc4f50182008-12-11 16:49:22 +01003921EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003922
3923/**
3924 * ring_buffer_reset - reset a ring buffer
3925 * @buffer: The ring buffer to reset all cpu buffers
3926 */
3927void ring_buffer_reset(struct ring_buffer *buffer)
3928{
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003929 int cpu;
3930
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003931 for_each_buffer_cpu(buffer, cpu)
Steven Rostedtd7690412008-10-01 00:29:53 -04003932 ring_buffer_reset_cpu(buffer, cpu);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003933}
Robert Richterc4f50182008-12-11 16:49:22 +01003934EXPORT_SYMBOL_GPL(ring_buffer_reset);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003935
3936/**
3937 * rind_buffer_empty - is the ring buffer empty?
3938 * @buffer: The ring buffer to test
3939 */
3940int ring_buffer_empty(struct ring_buffer *buffer)
3941{
3942 struct ring_buffer_per_cpu *cpu_buffer;
Steven Rostedtd4788202009-06-17 00:39:43 -04003943 unsigned long flags;
Steven Rostedt8d707e82009-06-16 21:22:48 -04003944 int dolock;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003945 int cpu;
Steven Rostedtd4788202009-06-17 00:39:43 -04003946 int ret;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003947
Steven Rostedt8d707e82009-06-16 21:22:48 -04003948 dolock = rb_ok_to_lock();
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003949
3950 /* yes this is racy, but if you don't like the race, lock the buffer */
3951 for_each_buffer_cpu(buffer, cpu) {
3952 cpu_buffer = buffer->buffers[cpu];
Steven Rostedt8d707e82009-06-16 21:22:48 -04003953 local_irq_save(flags);
3954 if (dolock)
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003955 raw_spin_lock(&cpu_buffer->reader_lock);
Steven Rostedtd4788202009-06-17 00:39:43 -04003956 ret = rb_per_cpu_empty(cpu_buffer);
Steven Rostedt8d707e82009-06-16 21:22:48 -04003957 if (dolock)
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003958 raw_spin_unlock(&cpu_buffer->reader_lock);
Steven Rostedt8d707e82009-06-16 21:22:48 -04003959 local_irq_restore(flags);
3960
Steven Rostedtd4788202009-06-17 00:39:43 -04003961 if (!ret)
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003962 return 0;
3963 }
Steven Rostedt554f7862009-03-11 22:00:13 -04003964
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003965 return 1;
3966}
Robert Richterc4f50182008-12-11 16:49:22 +01003967EXPORT_SYMBOL_GPL(ring_buffer_empty);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003968
3969/**
3970 * ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
3971 * @buffer: The ring buffer
3972 * @cpu: The CPU buffer to test
3973 */
3974int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
3975{
3976 struct ring_buffer_per_cpu *cpu_buffer;
Steven Rostedtd4788202009-06-17 00:39:43 -04003977 unsigned long flags;
Steven Rostedt8d707e82009-06-16 21:22:48 -04003978 int dolock;
Steven Rostedt8aabee52009-03-12 13:13:49 -04003979 int ret;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003980
Rusty Russell9e01c1b2009-01-01 10:12:22 +10303981 if (!cpumask_test_cpu(cpu, buffer->cpumask))
Steven Rostedt8aabee52009-03-12 13:13:49 -04003982 return 1;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003983
Steven Rostedt8d707e82009-06-16 21:22:48 -04003984 dolock = rb_ok_to_lock();
Steven Rostedt554f7862009-03-11 22:00:13 -04003985
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003986 cpu_buffer = buffer->buffers[cpu];
Steven Rostedt8d707e82009-06-16 21:22:48 -04003987 local_irq_save(flags);
3988 if (dolock)
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003989 raw_spin_lock(&cpu_buffer->reader_lock);
Steven Rostedt554f7862009-03-11 22:00:13 -04003990 ret = rb_per_cpu_empty(cpu_buffer);
Steven Rostedt8d707e82009-06-16 21:22:48 -04003991 if (dolock)
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02003992 raw_spin_unlock(&cpu_buffer->reader_lock);
Steven Rostedt8d707e82009-06-16 21:22:48 -04003993 local_irq_restore(flags);
Steven Rostedt554f7862009-03-11 22:00:13 -04003994
3995 return ret;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003996}
Robert Richterc4f50182008-12-11 16:49:22 +01003997EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04003998
Steven Rostedt85bac322009-09-04 14:24:40 -04003999#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04004000/**
4001 * ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
4002 * @buffer_a: One buffer to swap with
4003 * @buffer_b: The other buffer to swap with
4004 *
4005 * This function is useful for tracers that want to take a "snapshot"
4006 * of a CPU buffer and has another back up buffer lying around.
4007 * it is expected that the tracer handles the cpu buffer not being
4008 * used at the moment.
4009 */
4010int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
4011 struct ring_buffer *buffer_b, int cpu)
4012{
4013 struct ring_buffer_per_cpu *cpu_buffer_a;
4014 struct ring_buffer_per_cpu *cpu_buffer_b;
Steven Rostedt554f7862009-03-11 22:00:13 -04004015 int ret = -EINVAL;
4016
Rusty Russell9e01c1b2009-01-01 10:12:22 +10304017 if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
4018 !cpumask_test_cpu(cpu, buffer_b->cpumask))
Steven Rostedt554f7862009-03-11 22:00:13 -04004019 goto out;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04004020
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08004021 cpu_buffer_a = buffer_a->buffers[cpu];
4022 cpu_buffer_b = buffer_b->buffers[cpu];
4023
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04004024 /* At least make sure the two buffers are somewhat the same */
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08004025 if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
Steven Rostedt554f7862009-03-11 22:00:13 -04004026 goto out;
4027
4028 ret = -EAGAIN;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04004029
Steven Rostedt97b17ef2009-01-21 15:24:56 -05004030 if (ring_buffer_flags != RB_BUFFERS_ON)
Steven Rostedt554f7862009-03-11 22:00:13 -04004031 goto out;
Steven Rostedt97b17ef2009-01-21 15:24:56 -05004032
4033 if (atomic_read(&buffer_a->record_disabled))
Steven Rostedt554f7862009-03-11 22:00:13 -04004034 goto out;
Steven Rostedt97b17ef2009-01-21 15:24:56 -05004035
4036 if (atomic_read(&buffer_b->record_disabled))
Steven Rostedt554f7862009-03-11 22:00:13 -04004037 goto out;
Steven Rostedt97b17ef2009-01-21 15:24:56 -05004038
Steven Rostedt97b17ef2009-01-21 15:24:56 -05004039 if (atomic_read(&cpu_buffer_a->record_disabled))
Steven Rostedt554f7862009-03-11 22:00:13 -04004040 goto out;
Steven Rostedt97b17ef2009-01-21 15:24:56 -05004041
4042 if (atomic_read(&cpu_buffer_b->record_disabled))
Steven Rostedt554f7862009-03-11 22:00:13 -04004043 goto out;
Steven Rostedt97b17ef2009-01-21 15:24:56 -05004044
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04004045 /*
4046 * We can't do a synchronize_sched here because this
4047 * function can be called in atomic context.
4048 * Normally this will be called from the same CPU as cpu.
4049 * If not it's up to the caller to protect this.
4050 */
4051 atomic_inc(&cpu_buffer_a->record_disabled);
4052 atomic_inc(&cpu_buffer_b->record_disabled);
4053
Steven Rostedt98277992009-09-02 10:56:15 -04004054 ret = -EBUSY;
4055 if (local_read(&cpu_buffer_a->committing))
4056 goto out_dec;
4057 if (local_read(&cpu_buffer_b->committing))
4058 goto out_dec;
4059
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04004060 buffer_a->buffers[cpu] = cpu_buffer_b;
4061 buffer_b->buffers[cpu] = cpu_buffer_a;
4062
4063 cpu_buffer_b->buffer = buffer_a;
4064 cpu_buffer_a->buffer = buffer_b;
4065
Steven Rostedt98277992009-09-02 10:56:15 -04004066 ret = 0;
4067
4068out_dec:
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04004069 atomic_dec(&cpu_buffer_a->record_disabled);
4070 atomic_dec(&cpu_buffer_b->record_disabled);
Steven Rostedt554f7862009-03-11 22:00:13 -04004071out:
Steven Rostedt554f7862009-03-11 22:00:13 -04004072 return ret;
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04004073}
Robert Richterc4f50182008-12-11 16:49:22 +01004074EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
Steven Rostedt85bac322009-09-04 14:24:40 -04004075#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
Steven Rostedt7a8e76a2008-09-29 23:02:38 -04004076
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004077/**
4078 * ring_buffer_alloc_read_page - allocate a page to read from buffer
4079 * @buffer: the buffer to allocate for.
4080 *
4081 * This function is used in conjunction with ring_buffer_read_page.
4082 * When reading a full page from the ring buffer, these functions
4083 * can be used to speed up the process. The calling function should
4084 * allocate a few pages first with this function. Then when it
4085 * needs to get pages from the ring buffer, it passes the result
4086 * of this function into ring_buffer_read_page, which will swap
4087 * the page that was allocated, with the read page of the buffer.
4088 *
4089 * Returns:
4090 * The page allocated, or NULL on error.
4091 */
Vaibhav Nagarnaik7ea59062011-05-03 17:56:42 -07004092void *ring_buffer_alloc_read_page(struct ring_buffer *buffer, int cpu)
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004093{
Steven Rostedt044fa782008-12-02 23:50:03 -05004094 struct buffer_data_page *bpage;
Vaibhav Nagarnaik7ea59062011-05-03 17:56:42 -07004095 struct page *page;
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004096
Vaibhav Nagarnaikd7ec4bf2011-06-07 17:01:42 -07004097 page = alloc_pages_node(cpu_to_node(cpu),
4098 GFP_KERNEL | __GFP_NORETRY, 0);
Vaibhav Nagarnaik7ea59062011-05-03 17:56:42 -07004099 if (!page)
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004100 return NULL;
4101
Vaibhav Nagarnaik7ea59062011-05-03 17:56:42 -07004102 bpage = page_address(page);
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004103
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004104 rb_init_page(bpage);
4105
Steven Rostedt044fa782008-12-02 23:50:03 -05004106 return bpage;
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004107}
Steven Rostedtd6ce96d2009-05-05 01:15:24 -04004108EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004109
4110/**
4111 * ring_buffer_free_read_page - free an allocated read page
4112 * @buffer: the buffer the page was allocate for
4113 * @data: the page to free
4114 *
4115 * Free a page allocated from ring_buffer_alloc_read_page.
4116 */
4117void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
4118{
4119 free_page((unsigned long)data);
4120}
Steven Rostedtd6ce96d2009-05-05 01:15:24 -04004121EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004122
4123/**
4124 * ring_buffer_read_page - extract a page from the ring buffer
4125 * @buffer: buffer to extract from
4126 * @data_page: the page to use allocated from ring_buffer_alloc_read_page
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004127 * @len: amount to extract
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004128 * @cpu: the cpu of the buffer to extract
4129 * @full: should the extraction only happen when the page is full.
4130 *
4131 * This function will pull out a page from the ring buffer and consume it.
4132 * @data_page must be the address of the variable that was returned
4133 * from ring_buffer_alloc_read_page. This is because the page might be used
4134 * to swap with a page in the ring buffer.
4135 *
4136 * for example:
Lai Jiangshanb85fa012009-02-09 14:21:14 +08004137 * rpage = ring_buffer_alloc_read_page(buffer);
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004138 * if (!rpage)
4139 * return error;
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004140 * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
Lai Jiangshan667d2412009-02-09 14:21:17 +08004141 * if (ret >= 0)
4142 * process_page(rpage, ret);
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004143 *
4144 * When @full is set, the function will not return true unless
4145 * the writer is off the reader page.
4146 *
4147 * Note: it is up to the calling functions to handle sleeps and wakeups.
4148 * The ring buffer can be used anywhere in the kernel and can not
4149 * blindly call wake_up. The layer that uses the ring buffer must be
4150 * responsible for that.
4151 *
4152 * Returns:
Lai Jiangshan667d2412009-02-09 14:21:17 +08004153 * >=0 if data has been transferred, returns the offset of consumed data.
4154 * <0 if no data has been transferred.
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004155 */
4156int ring_buffer_read_page(struct ring_buffer *buffer,
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004157 void **data_page, size_t len, int cpu, int full)
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004158{
4159 struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
4160 struct ring_buffer_event *event;
Steven Rostedt044fa782008-12-02 23:50:03 -05004161 struct buffer_data_page *bpage;
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004162 struct buffer_page *reader;
Steven Rostedtff0ff842010-03-31 22:11:42 -04004163 unsigned long missed_events;
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004164 unsigned long flags;
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004165 unsigned int commit;
Lai Jiangshan667d2412009-02-09 14:21:17 +08004166 unsigned int read;
Steven Rostedt4f3640f2009-03-03 23:52:42 -05004167 u64 save_timestamp;
Lai Jiangshan667d2412009-02-09 14:21:17 +08004168 int ret = -1;
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004169
Steven Rostedt554f7862009-03-11 22:00:13 -04004170 if (!cpumask_test_cpu(cpu, buffer->cpumask))
4171 goto out;
4172
Steven Rostedt474d32b2009-03-03 19:51:40 -05004173 /*
4174 * If len is not big enough to hold the page header, then
4175 * we can not copy anything.
4176 */
4177 if (len <= BUF_PAGE_HDR_SIZE)
Steven Rostedt554f7862009-03-11 22:00:13 -04004178 goto out;
Steven Rostedt474d32b2009-03-03 19:51:40 -05004179
4180 len -= BUF_PAGE_HDR_SIZE;
4181
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004182 if (!data_page)
Steven Rostedt554f7862009-03-11 22:00:13 -04004183 goto out;
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004184
Steven Rostedt044fa782008-12-02 23:50:03 -05004185 bpage = *data_page;
4186 if (!bpage)
Steven Rostedt554f7862009-03-11 22:00:13 -04004187 goto out;
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004188
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02004189 raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004190
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004191 reader = rb_get_reader_page(cpu_buffer);
4192 if (!reader)
Steven Rostedt554f7862009-03-11 22:00:13 -04004193 goto out_unlock;
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004194
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004195 event = rb_reader_event(cpu_buffer);
Lai Jiangshan667d2412009-02-09 14:21:17 +08004196
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004197 read = reader->read;
4198 commit = rb_page_commit(reader);
4199
Steven Rostedt66a8cb92010-03-31 13:21:56 -04004200 /* Check if any events were dropped */
Steven Rostedtff0ff842010-03-31 22:11:42 -04004201 missed_events = cpu_buffer->lost_events;
Steven Rostedt66a8cb92010-03-31 13:21:56 -04004202
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004203 /*
Steven Rostedt474d32b2009-03-03 19:51:40 -05004204 * If this page has been partially read or
4205 * if len is not big enough to read the rest of the page or
4206 * a writer is still on the page, then
4207 * we must copy the data from the page to the buffer.
4208 * Otherwise, we can simply swap the page with the one passed in.
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004209 */
Steven Rostedt474d32b2009-03-03 19:51:40 -05004210 if (read || (len < (commit - read)) ||
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004211 cpu_buffer->reader_page == cpu_buffer->commit_page) {
Lai Jiangshan667d2412009-02-09 14:21:17 +08004212 struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
Steven Rostedt474d32b2009-03-03 19:51:40 -05004213 unsigned int rpos = read;
4214 unsigned int pos = 0;
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004215 unsigned int size;
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004216
4217 if (full)
Steven Rostedt554f7862009-03-11 22:00:13 -04004218 goto out_unlock;
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004219
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004220 if (len > (commit - read))
4221 len = (commit - read);
4222
Steven Rostedt69d1b832010-10-07 18:18:05 -04004223 /* Always keep the time extend and data together */
4224 size = rb_event_ts_length(event);
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004225
4226 if (len < size)
Steven Rostedt554f7862009-03-11 22:00:13 -04004227 goto out_unlock;
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004228
Steven Rostedt4f3640f2009-03-03 23:52:42 -05004229 /* save the current timestamp, since the user will need it */
4230 save_timestamp = cpu_buffer->read_stamp;
4231
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004232 /* Need to copy one event at a time */
4233 do {
David Sharpe1e35922010-12-22 16:38:24 -08004234 /* We need the size of one event, because
4235 * rb_advance_reader only advances by one event,
4236 * whereas rb_event_ts_length may include the size of
4237 * one or two events.
4238 * We have already ensured there's enough space if this
4239 * is a time extend. */
4240 size = rb_event_length(event);
Steven Rostedt474d32b2009-03-03 19:51:40 -05004241 memcpy(bpage->data + pos, rpage->data + rpos, size);
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004242
4243 len -= size;
4244
4245 rb_advance_reader(cpu_buffer);
Steven Rostedt474d32b2009-03-03 19:51:40 -05004246 rpos = reader->read;
4247 pos += size;
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004248
Huang Ying18fab912010-07-28 14:14:01 +08004249 if (rpos >= commit)
4250 break;
4251
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004252 event = rb_reader_event(cpu_buffer);
Steven Rostedt69d1b832010-10-07 18:18:05 -04004253 /* Always keep the time extend and data together */
4254 size = rb_event_ts_length(event);
David Sharpe1e35922010-12-22 16:38:24 -08004255 } while (len >= size);
Lai Jiangshan667d2412009-02-09 14:21:17 +08004256
4257 /* update bpage */
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004258 local_set(&bpage->commit, pos);
Steven Rostedt4f3640f2009-03-03 23:52:42 -05004259 bpage->time_stamp = save_timestamp;
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004260
Steven Rostedt474d32b2009-03-03 19:51:40 -05004261 /* we copied everything to the beginning */
4262 read = 0;
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004263 } else {
Steven Rostedtafbab762009-05-01 19:40:05 -04004264 /* update the entry counter */
Steven Rostedt77ae3652009-03-27 11:00:29 -04004265 cpu_buffer->read += rb_page_entries(reader);
Vaibhav Nagarnaikc64e1482011-08-16 14:46:16 -07004266 cpu_buffer->read_bytes += BUF_PAGE_SIZE;
Steven Rostedtafbab762009-05-01 19:40:05 -04004267
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004268 /* swap the pages */
Steven Rostedt044fa782008-12-02 23:50:03 -05004269 rb_init_page(bpage);
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004270 bpage = reader->page;
4271 reader->page = *data_page;
4272 local_set(&reader->write, 0);
Steven Rostedt778c55d2009-05-01 18:44:45 -04004273 local_set(&reader->entries, 0);
Steven Rostedtef7a4a12009-03-03 00:27:49 -05004274 reader->read = 0;
Steven Rostedt044fa782008-12-02 23:50:03 -05004275 *data_page = bpage;
Steven Rostedtff0ff842010-03-31 22:11:42 -04004276
4277 /*
4278 * Use the real_end for the data size,
4279 * This gives us a chance to store the lost events
4280 * on the page.
4281 */
4282 if (reader->real_end)
4283 local_set(&bpage->commit, reader->real_end);
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004284 }
Lai Jiangshan667d2412009-02-09 14:21:17 +08004285 ret = read;
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004286
Steven Rostedt66a8cb92010-03-31 13:21:56 -04004287 cpu_buffer->lost_events = 0;
Steven Rostedt2711ca22010-05-21 13:32:26 -04004288
4289 commit = local_read(&bpage->commit);
Steven Rostedt66a8cb92010-03-31 13:21:56 -04004290 /*
4291 * Set a flag in the commit field if we lost events
4292 */
Steven Rostedtff0ff842010-03-31 22:11:42 -04004293 if (missed_events) {
Steven Rostedtff0ff842010-03-31 22:11:42 -04004294 /* If there is room at the end of the page to save the
4295 * missed events, then record it there.
4296 */
4297 if (BUF_PAGE_SIZE - commit >= sizeof(missed_events)) {
4298 memcpy(&bpage->data[commit], &missed_events,
4299 sizeof(missed_events));
4300 local_add(RB_MISSED_STORED, &bpage->commit);
Steven Rostedt2711ca22010-05-21 13:32:26 -04004301 commit += sizeof(missed_events);
Steven Rostedtff0ff842010-03-31 22:11:42 -04004302 }
Steven Rostedt66a8cb92010-03-31 13:21:56 -04004303 local_add(RB_MISSED_EVENTS, &bpage->commit);
Steven Rostedtff0ff842010-03-31 22:11:42 -04004304 }
Steven Rostedt66a8cb92010-03-31 13:21:56 -04004305
Steven Rostedt2711ca22010-05-21 13:32:26 -04004306 /*
4307 * This page may be off to user land. Zero it out here.
4308 */
4309 if (commit < BUF_PAGE_SIZE)
4310 memset(&bpage->data[commit], 0, BUF_PAGE_SIZE - commit);
4311
Steven Rostedt554f7862009-03-11 22:00:13 -04004312 out_unlock:
Thomas Gleixner5389f6f2009-07-25 17:13:33 +02004313 raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004314
Steven Rostedt554f7862009-03-11 22:00:13 -04004315 out:
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004316 return ret;
4317}
Steven Rostedtd6ce96d2009-05-05 01:15:24 -04004318EXPORT_SYMBOL_GPL(ring_buffer_read_page);
Steven Rostedt8789a9e2008-12-02 15:34:07 -05004319
Steven Rostedt59222ef2009-03-12 11:46:03 -04004320#ifdef CONFIG_HOTPLUG_CPU
Frederic Weisbecker09c9e842009-03-21 04:33:36 +01004321static int rb_cpu_notify(struct notifier_block *self,
4322 unsigned long action, void *hcpu)
Steven Rostedt554f7862009-03-11 22:00:13 -04004323{
4324 struct ring_buffer *buffer =
4325 container_of(self, struct ring_buffer, cpu_notify);
4326 long cpu = (long)hcpu;
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08004327 int cpu_i, nr_pages_same;
4328 unsigned int nr_pages;
Steven Rostedt554f7862009-03-11 22:00:13 -04004329
4330 switch (action) {
4331 case CPU_UP_PREPARE:
4332 case CPU_UP_PREPARE_FROZEN:
Rusty Russell3f237a72009-06-12 21:15:30 +09304333 if (cpumask_test_cpu(cpu, buffer->cpumask))
Steven Rostedt554f7862009-03-11 22:00:13 -04004334 return NOTIFY_OK;
4335
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08004336 nr_pages = 0;
4337 nr_pages_same = 1;
4338 /* check if all cpu sizes are same */
4339 for_each_buffer_cpu(buffer, cpu_i) {
4340 /* fill in the size from first enabled cpu */
4341 if (nr_pages == 0)
4342 nr_pages = buffer->buffers[cpu_i]->nr_pages;
4343 if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
4344 nr_pages_same = 0;
4345 break;
4346 }
4347 }
4348 /* allocate minimum pages, user can later expand it */
4349 if (!nr_pages_same)
4350 nr_pages = 2;
Steven Rostedt554f7862009-03-11 22:00:13 -04004351 buffer->buffers[cpu] =
Vaibhav Nagarnaik438ced12012-02-02 12:00:41 -08004352 rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
Steven Rostedt554f7862009-03-11 22:00:13 -04004353 if (!buffer->buffers[cpu]) {
4354 WARN(1, "failed to allocate ring buffer on CPU %ld\n",
4355 cpu);
4356 return NOTIFY_OK;
4357 }
4358 smp_wmb();
Rusty Russell3f237a72009-06-12 21:15:30 +09304359 cpumask_set_cpu(cpu, buffer->cpumask);
Steven Rostedt554f7862009-03-11 22:00:13 -04004360 break;
4361 case CPU_DOWN_PREPARE:
4362 case CPU_DOWN_PREPARE_FROZEN:
4363 /*
4364 * Do nothing.
4365 * If we were to free the buffer, then the user would
4366 * lose any trace that was in the buffer.
4367 */
4368 break;
4369 default:
4370 break;
4371 }
4372 return NOTIFY_OK;
4373}
4374#endif