oprofile: modify op_cpu_buffer_read_entry()
[linux-2.6.git] / drivers / oprofile / cpu_buffer.c
1 /**
2  * @file cpu_buffer.c
3  *
4  * @remark Copyright 2002-2009 OProfile authors
5  * @remark Read the file COPYING
6  *
7  * @author John Levon <levon@movementarian.org>
8  * @author Barry Kasindorf <barry.kasindorf@amd.com>
9  * @author Robert Richter <robert.richter@amd.com>
10  *
11  * Each CPU has a local buffer that stores PC value/event
12  * pairs. We also log context switches when we notice them.
13  * Eventually each CPU's buffer is processed into the global
14  * event buffer by sync_buffer().
15  *
16  * We use a local buffer for two reasons: an NMI or similar
17  * interrupt cannot synchronise, and high sampling rates
18  * would lead to catastrophic global synchronisation if
19  * a global buffer was used.
20  */
21
22 #include <linux/sched.h>
23 #include <linux/oprofile.h>
24 #include <linux/vmalloc.h>
25 #include <linux/errno.h>
26
27 #include "event_buffer.h"
28 #include "cpu_buffer.h"
29 #include "buffer_sync.h"
30 #include "oprof.h"
31
32 #define OP_BUFFER_FLAGS 0
33
34 /*
35  * Read and write access is using spin locking. Thus, writing to the
36  * buffer by NMI handler (x86) could occur also during critical
37  * sections when reading the buffer. To avoid this, there are 2
38  * buffers for independent read and write access. Read access is in
39  * process context only, write access only in the NMI handler. If the
40  * read buffer runs empty, both buffers are swapped atomically. There
41  * is potentially a small window during swapping where the buffers are
42  * disabled and samples could be lost.
43  *
44  * Using 2 buffers is a little bit overhead, but the solution is clear
45  * and does not require changes in the ring buffer implementation. It
46  * can be changed to a single buffer solution when the ring buffer
47  * access is implemented as non-locking atomic code.
48  */
49 static struct ring_buffer *op_ring_buffer_read;
50 static struct ring_buffer *op_ring_buffer_write;
51 DEFINE_PER_CPU(struct oprofile_cpu_buffer, cpu_buffer);
52
53 static void wq_sync_buffer(struct work_struct *work);
54
55 #define DEFAULT_TIMER_EXPIRE (HZ / 10)
56 static int work_enabled;
57
58 unsigned long oprofile_get_cpu_buffer_size(void)
59 {
60         return oprofile_cpu_buffer_size;
61 }
62
63 void oprofile_cpu_buffer_inc_smpl_lost(void)
64 {
65         struct oprofile_cpu_buffer *cpu_buf
66                 = &__get_cpu_var(cpu_buffer);
67
68         cpu_buf->sample_lost_overflow++;
69 }
70
71 void free_cpu_buffers(void)
72 {
73         if (op_ring_buffer_read)
74                 ring_buffer_free(op_ring_buffer_read);
75         op_ring_buffer_read = NULL;
76         if (op_ring_buffer_write)
77                 ring_buffer_free(op_ring_buffer_write);
78         op_ring_buffer_write = NULL;
79 }
80
81 int alloc_cpu_buffers(void)
82 {
83         int i;
84
85         unsigned long buffer_size = oprofile_cpu_buffer_size;
86
87         op_ring_buffer_read = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS);
88         if (!op_ring_buffer_read)
89                 goto fail;
90         op_ring_buffer_write = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS);
91         if (!op_ring_buffer_write)
92                 goto fail;
93
94         for_each_possible_cpu(i) {
95                 struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
96
97                 b->last_task = NULL;
98                 b->last_is_kernel = -1;
99                 b->tracing = 0;
100                 b->buffer_size = buffer_size;
101                 b->sample_received = 0;
102                 b->sample_lost_overflow = 0;
103                 b->backtrace_aborted = 0;
104                 b->sample_invalid_eip = 0;
105                 b->cpu = i;
106                 INIT_DELAYED_WORK(&b->work, wq_sync_buffer);
107         }
108         return 0;
109
110 fail:
111         free_cpu_buffers();
112         return -ENOMEM;
113 }
114
115 void start_cpu_work(void)
116 {
117         int i;
118
119         work_enabled = 1;
120
121         for_each_online_cpu(i) {
122                 struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
123
124                 /*
125                  * Spread the work by 1 jiffy per cpu so they dont all
126                  * fire at once.
127                  */
128                 schedule_delayed_work_on(i, &b->work, DEFAULT_TIMER_EXPIRE + i);
129         }
130 }
131
132 void end_cpu_work(void)
133 {
134         int i;
135
136         work_enabled = 0;
137
138         for_each_online_cpu(i) {
139                 struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
140
141                 cancel_delayed_work(&b->work);
142         }
143
144         flush_scheduled_work();
145 }
146
147 /*
148  * This function prepares the cpu buffer to write a sample.
149  *
150  * Struct op_entry is used during operations on the ring buffer while
151  * struct op_sample contains the data that is stored in the ring
152  * buffer. Struct entry can be uninitialized. The function reserves a
153  * data array that is specified by size. Use
154  * op_cpu_buffer_write_commit() after preparing the sample. In case of
155  * errors a null pointer is returned, otherwise the pointer to the
156  * sample.
157  *
158  */
159 struct op_sample
160 *op_cpu_buffer_write_reserve(struct op_entry *entry, unsigned long size)
161 {
162         entry->event = ring_buffer_lock_reserve
163                 (op_ring_buffer_write, sizeof(struct op_sample) +
164                  size * sizeof(entry->sample->data[0]), &entry->irq_flags);
165         if (entry->event)
166                 entry->sample = ring_buffer_event_data(entry->event);
167         else
168                 entry->sample = NULL;
169
170         if (!entry->sample)
171                 return NULL;
172
173         entry->size = size;
174         entry->data = entry->sample->data;
175
176         return entry->sample;
177 }
178
179 int op_cpu_buffer_write_commit(struct op_entry *entry)
180 {
181         return ring_buffer_unlock_commit(op_ring_buffer_write, entry->event,
182                                          entry->irq_flags);
183 }
184
185 struct op_sample *op_cpu_buffer_read_entry(struct op_entry *entry, int cpu)
186 {
187         struct ring_buffer_event *e;
188         e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL);
189         if (e)
190                 goto event;
191         if (ring_buffer_swap_cpu(op_ring_buffer_read,
192                                  op_ring_buffer_write,
193                                  cpu))
194                 return NULL;
195         e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL);
196         if (e)
197                 goto event;
198         return NULL;
199
200 event:
201         entry->event = e;
202         entry->sample = ring_buffer_event_data(e);
203         entry->size = (ring_buffer_event_length(e) - sizeof(struct op_sample))
204                 / sizeof(entry->sample->data[0]);
205         entry->data = entry->sample->data;
206         return entry->sample;
207 }
208
209 unsigned long op_cpu_buffer_entries(int cpu)
210 {
211         return ring_buffer_entries_cpu(op_ring_buffer_read, cpu)
212                 + ring_buffer_entries_cpu(op_ring_buffer_write, cpu);
213 }
214
215 static inline int
216 op_add_sample(struct oprofile_cpu_buffer *cpu_buf,
217               unsigned long pc, unsigned long event)
218 {
219         struct op_entry entry;
220         struct op_sample *sample;
221
222         sample = op_cpu_buffer_write_reserve(&entry, 0);
223         if (!sample)
224                 return -ENOMEM;
225
226         sample->eip = pc;
227         sample->event = event;
228
229         return op_cpu_buffer_write_commit(&entry);
230 }
231
232 static inline int
233 add_code(struct oprofile_cpu_buffer *buffer, unsigned long value)
234 {
235         return op_add_sample(buffer, ESCAPE_CODE, value);
236 }
237
238 /* This must be safe from any context. It's safe writing here
239  * because of the head/tail separation of the writer and reader
240  * of the CPU buffer.
241  *
242  * is_kernel is needed because on some architectures you cannot
243  * tell if you are in kernel or user space simply by looking at
244  * pc. We tag this in the buffer by generating kernel enter/exit
245  * events whenever is_kernel changes
246  */
247 static int log_sample(struct oprofile_cpu_buffer *cpu_buf, unsigned long pc,
248                       int is_kernel, unsigned long event)
249 {
250         struct task_struct *task;
251
252         cpu_buf->sample_received++;
253
254         if (pc == ESCAPE_CODE) {
255                 cpu_buf->sample_invalid_eip++;
256                 return 0;
257         }
258
259         is_kernel = !!is_kernel;
260
261         task = current;
262
263         /* notice a switch from user->kernel or vice versa */
264         if (cpu_buf->last_is_kernel != is_kernel) {
265                 cpu_buf->last_is_kernel = is_kernel;
266                 if (add_code(cpu_buf, is_kernel))
267                         goto fail;
268         }
269
270         /* notice a task switch */
271         if (cpu_buf->last_task != task) {
272                 cpu_buf->last_task = task;
273                 if (add_code(cpu_buf, (unsigned long)task))
274                         goto fail;
275         }
276
277         if (op_add_sample(cpu_buf, pc, event))
278                 goto fail;
279
280         return 1;
281
282 fail:
283         cpu_buf->sample_lost_overflow++;
284         return 0;
285 }
286
287 static inline void oprofile_begin_trace(struct oprofile_cpu_buffer *cpu_buf)
288 {
289         add_code(cpu_buf, CPU_TRACE_BEGIN);
290         cpu_buf->tracing = 1;
291 }
292
293 static inline void oprofile_end_trace(struct oprofile_cpu_buffer *cpu_buf)
294 {
295         cpu_buf->tracing = 0;
296 }
297
298 static inline void
299 __oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
300                           unsigned long event, int is_kernel)
301 {
302         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
303
304         if (!oprofile_backtrace_depth) {
305                 log_sample(cpu_buf, pc, is_kernel, event);
306                 return;
307         }
308
309         oprofile_begin_trace(cpu_buf);
310
311         /*
312          * if log_sample() fail we can't backtrace since we lost the
313          * source of this event
314          */
315         if (log_sample(cpu_buf, pc, is_kernel, event))
316                 oprofile_ops.backtrace(regs, oprofile_backtrace_depth);
317
318         oprofile_end_trace(cpu_buf);
319 }
320
321 void oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
322                              unsigned long event, int is_kernel)
323 {
324         __oprofile_add_ext_sample(pc, regs, event, is_kernel);
325 }
326
327 void oprofile_add_sample(struct pt_regs * const regs, unsigned long event)
328 {
329         int is_kernel = !user_mode(regs);
330         unsigned long pc = profile_pc(regs);
331
332         __oprofile_add_ext_sample(pc, regs, event, is_kernel);
333 }
334
335 #ifdef CONFIG_OPROFILE_IBS
336
337 void oprofile_add_ibs_sample(struct pt_regs * const regs,
338                              unsigned int * const ibs_sample, int ibs_code)
339 {
340         int is_kernel = !user_mode(regs);
341         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
342         struct task_struct *task;
343         int fail = 0;
344
345         cpu_buf->sample_received++;
346
347         /* notice a switch from user->kernel or vice versa */
348         if (cpu_buf->last_is_kernel != is_kernel) {
349                 if (add_code(cpu_buf, is_kernel))
350                         goto fail;
351                 cpu_buf->last_is_kernel = is_kernel;
352         }
353
354         /* notice a task switch */
355         if (!is_kernel) {
356                 task = current;
357                 if (cpu_buf->last_task != task) {
358                         if (add_code(cpu_buf, (unsigned long)task))
359                                 goto fail;
360                         cpu_buf->last_task = task;
361                 }
362         }
363
364         fail = fail || add_code(cpu_buf, ibs_code);
365         fail = fail || op_add_sample(cpu_buf, ibs_sample[0], ibs_sample[1]);
366         fail = fail || op_add_sample(cpu_buf, ibs_sample[2], ibs_sample[3]);
367         fail = fail || op_add_sample(cpu_buf, ibs_sample[4], ibs_sample[5]);
368
369         if (ibs_code == IBS_OP_BEGIN) {
370                 fail = fail || op_add_sample(cpu_buf, ibs_sample[6], ibs_sample[7]);
371                 fail = fail || op_add_sample(cpu_buf, ibs_sample[8], ibs_sample[9]);
372                 fail = fail || op_add_sample(cpu_buf, ibs_sample[10], ibs_sample[11]);
373         }
374
375         if (!fail)
376                 return;
377
378 fail:
379         cpu_buf->sample_lost_overflow++;
380 }
381
382 #endif
383
384 void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event)
385 {
386         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
387         log_sample(cpu_buf, pc, is_kernel, event);
388 }
389
390 void oprofile_add_trace(unsigned long pc)
391 {
392         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
393
394         if (!cpu_buf->tracing)
395                 return;
396
397         /*
398          * broken frame can give an eip with the same value as an
399          * escape code, abort the trace if we get it
400          */
401         if (pc == ESCAPE_CODE)
402                 goto fail;
403
404         if (op_add_sample(cpu_buf, pc, 0))
405                 goto fail;
406
407         return;
408 fail:
409         cpu_buf->tracing = 0;
410         cpu_buf->backtrace_aborted++;
411         return;
412 }
413
414 /*
415  * This serves to avoid cpu buffer overflow, and makes sure
416  * the task mortuary progresses
417  *
418  * By using schedule_delayed_work_on and then schedule_delayed_work
419  * we guarantee this will stay on the correct cpu
420  */
421 static void wq_sync_buffer(struct work_struct *work)
422 {
423         struct oprofile_cpu_buffer *b =
424                 container_of(work, struct oprofile_cpu_buffer, work.work);
425         if (b->cpu != smp_processor_id()) {
426                 printk(KERN_DEBUG "WQ on CPU%d, prefer CPU%d\n",
427                        smp_processor_id(), b->cpu);
428
429                 if (!cpu_online(b->cpu)) {
430                         cancel_delayed_work(&b->work);
431                         return;
432                 }
433         }
434         sync_buffer(b->cpu);
435
436         /* don't re-add the work if we're shutting down */
437         if (work_enabled)
438                 schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE);
439 }