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