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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/**
2 * @file buffer_sync.c
3 *
4 * @remark Copyright 2002 OProfile authors
5 * @remark Read the file COPYING
6 *
7 * @author John Levon <levon@movementarian.org>
8 *
9 * This is the core of the buffer management. Each
10 * CPU buffer is processed and entered into the
11 * global event buffer. Such processing is necessary
12 * in several circumstances, mentioned below.
13 *
14 * The processing does the job of converting the
15 * transitory EIP value into a persistent dentry/offset
16 * value that the profiler can record at its leisure.
17 *
18 * See fs/dcookies.c for a description of the dentry/offset
19 * objects.
20 */
21
22#include <linux/mm.h>
23#include <linux/workqueue.h>
24#include <linux/notifier.h>
25#include <linux/dcookies.h>
26#include <linux/profile.h>
27#include <linux/module.h>
28#include <linux/fs.h>
Alexey Dobriyane8edc6e2007-05-21 01:22:52 +040029#include <linux/sched.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070030
31#include "oprofile_stats.h"
32#include "event_buffer.h"
33#include "cpu_buffer.h"
34#include "buffer_sync.h"
35
36static LIST_HEAD(dying_tasks);
37static LIST_HEAD(dead_tasks);
38static cpumask_t marked_cpus = CPU_MASK_NONE;
39static DEFINE_SPINLOCK(task_mortuary);
40static void process_task_mortuary(void);
41
42
43/* Take ownership of the task struct and place it on the
44 * list for processing. Only after two full buffer syncs
45 * does the task eventually get freed, because by then
46 * we are sure we will not reference it again.
Paul E. McKenney4369ef32006-01-08 01:01:35 -080047 * Can be invoked from softirq via RCU callback due to
48 * call_rcu() of the task struct, hence the _irqsave.
Linus Torvalds1da177e2005-04-16 15:20:36 -070049 */
50static int task_free_notify(struct notifier_block * self, unsigned long val, void * data)
51{
Paul E. McKenney4369ef32006-01-08 01:01:35 -080052 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 struct task_struct * task = data;
Paul E. McKenney4369ef32006-01-08 01:01:35 -080054 spin_lock_irqsave(&task_mortuary, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -070055 list_add(&task->tasks, &dying_tasks);
Paul E. McKenney4369ef32006-01-08 01:01:35 -080056 spin_unlock_irqrestore(&task_mortuary, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -070057 return NOTIFY_OK;
58}
59
60
61/* The task is on its way out. A sync of the buffer means we can catch
62 * any remaining samples for this task.
63 */
64static int task_exit_notify(struct notifier_block * self, unsigned long val, void * data)
65{
66 /* To avoid latency problems, we only process the current CPU,
67 * hoping that most samples for the task are on this CPU
68 */
Ingo Molnar39c715b2005-06-21 17:14:34 -070069 sync_buffer(raw_smp_processor_id());
Linus Torvalds1da177e2005-04-16 15:20:36 -070070 return 0;
71}
72
73
74/* The task is about to try a do_munmap(). We peek at what it's going to
75 * do, and if it's an executable region, process the samples first, so
76 * we don't lose any. This does not have to be exact, it's a QoI issue
77 * only.
78 */
79static int munmap_notify(struct notifier_block * self, unsigned long val, void * data)
80{
81 unsigned long addr = (unsigned long)data;
82 struct mm_struct * mm = current->mm;
83 struct vm_area_struct * mpnt;
84
85 down_read(&mm->mmap_sem);
86
87 mpnt = find_vma(mm, addr);
88 if (mpnt && mpnt->vm_file && (mpnt->vm_flags & VM_EXEC)) {
89 up_read(&mm->mmap_sem);
90 /* To avoid latency problems, we only process the current CPU,
91 * hoping that most samples for the task are on this CPU
92 */
Ingo Molnar39c715b2005-06-21 17:14:34 -070093 sync_buffer(raw_smp_processor_id());
Linus Torvalds1da177e2005-04-16 15:20:36 -070094 return 0;
95 }
96
97 up_read(&mm->mmap_sem);
98 return 0;
99}
100
101
102/* We need to be told about new modules so we don't attribute to a previously
103 * loaded module, or drop the samples on the floor.
104 */
105static int module_load_notify(struct notifier_block * self, unsigned long val, void * data)
106{
107#ifdef CONFIG_MODULES
108 if (val != MODULE_STATE_COMING)
109 return 0;
110
111 /* FIXME: should we process all CPU buffers ? */
Markus Armbruster59cc1852006-06-25 05:47:33 -0700112 mutex_lock(&buffer_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113 add_event_entry(ESCAPE_CODE);
114 add_event_entry(MODULE_LOADED_CODE);
Markus Armbruster59cc1852006-06-25 05:47:33 -0700115 mutex_unlock(&buffer_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116#endif
117 return 0;
118}
119
120
121static struct notifier_block task_free_nb = {
122 .notifier_call = task_free_notify,
123};
124
125static struct notifier_block task_exit_nb = {
126 .notifier_call = task_exit_notify,
127};
128
129static struct notifier_block munmap_nb = {
130 .notifier_call = munmap_notify,
131};
132
133static struct notifier_block module_load_nb = {
134 .notifier_call = module_load_notify,
135};
136
137
138static void end_sync(void)
139{
140 end_cpu_work();
141 /* make sure we don't leak task structs */
142 process_task_mortuary();
143 process_task_mortuary();
144}
145
146
147int sync_start(void)
148{
149 int err;
150
151 start_cpu_work();
152
153 err = task_handoff_register(&task_free_nb);
154 if (err)
155 goto out1;
156 err = profile_event_register(PROFILE_TASK_EXIT, &task_exit_nb);
157 if (err)
158 goto out2;
159 err = profile_event_register(PROFILE_MUNMAP, &munmap_nb);
160 if (err)
161 goto out3;
162 err = register_module_notifier(&module_load_nb);
163 if (err)
164 goto out4;
165
166out:
167 return err;
168out4:
169 profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
170out3:
171 profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
172out2:
173 task_handoff_unregister(&task_free_nb);
174out1:
175 end_sync();
176 goto out;
177}
178
179
180void sync_stop(void)
181{
182 unregister_module_notifier(&module_load_nb);
183 profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
184 profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
185 task_handoff_unregister(&task_free_nb);
186 end_sync();
187}
188
189
190/* Optimisation. We can manage without taking the dcookie sem
191 * because we cannot reach this code without at least one
192 * dcookie user still being registered (namely, the reader
193 * of the event buffer). */
194static inline unsigned long fast_get_dcookie(struct dentry * dentry,
195 struct vfsmount * vfsmnt)
196{
197 unsigned long cookie;
198
199 if (dentry->d_cookie)
200 return (unsigned long)dentry;
201 get_dcookie(dentry, vfsmnt, &cookie);
202 return cookie;
203}
204
205
206/* Look up the dcookie for the task's first VM_EXECUTABLE mapping,
207 * which corresponds loosely to "application name". This is
208 * not strictly necessary but allows oprofile to associate
209 * shared-library samples with particular applications
210 */
211static unsigned long get_exec_dcookie(struct mm_struct * mm)
212{
John Levon0c0a4002005-06-23 22:02:47 -0700213 unsigned long cookie = NO_COOKIE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214 struct vm_area_struct * vma;
215
216 if (!mm)
217 goto out;
218
219 for (vma = mm->mmap; vma; vma = vma->vm_next) {
220 if (!vma->vm_file)
221 continue;
222 if (!(vma->vm_flags & VM_EXECUTABLE))
223 continue;
Josef Sipek1fb14302006-12-08 02:37:27 -0800224 cookie = fast_get_dcookie(vma->vm_file->f_path.dentry,
225 vma->vm_file->f_path.mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700226 break;
227 }
228
229out:
230 return cookie;
231}
232
233
234/* Convert the EIP value of a sample into a persistent dentry/offset
235 * pair that can then be added to the global event buffer. We make
236 * sure to do this lookup before a mm->mmap modification happens so
237 * we don't lose track.
238 */
239static unsigned long lookup_dcookie(struct mm_struct * mm, unsigned long addr, off_t * offset)
240{
John Levon0c0a4002005-06-23 22:02:47 -0700241 unsigned long cookie = NO_COOKIE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242 struct vm_area_struct * vma;
243
244 for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
245
Linus Torvalds1da177e2005-04-16 15:20:36 -0700246 if (addr < vma->vm_start || addr >= vma->vm_end)
247 continue;
248
John Levon0c0a4002005-06-23 22:02:47 -0700249 if (vma->vm_file) {
Josef Sipek1fb14302006-12-08 02:37:27 -0800250 cookie = fast_get_dcookie(vma->vm_file->f_path.dentry,
251 vma->vm_file->f_path.mnt);
John Levon0c0a4002005-06-23 22:02:47 -0700252 *offset = (vma->vm_pgoff << PAGE_SHIFT) + addr -
253 vma->vm_start;
254 } else {
255 /* must be an anonymous map */
256 *offset = addr;
257 }
258
Linus Torvalds1da177e2005-04-16 15:20:36 -0700259 break;
260 }
261
John Levon0c0a4002005-06-23 22:02:47 -0700262 if (!vma)
263 cookie = INVALID_COOKIE;
264
Linus Torvalds1da177e2005-04-16 15:20:36 -0700265 return cookie;
266}
267
268
John Levon0c0a4002005-06-23 22:02:47 -0700269static unsigned long last_cookie = INVALID_COOKIE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700270
271static void add_cpu_switch(int i)
272{
273 add_event_entry(ESCAPE_CODE);
274 add_event_entry(CPU_SWITCH_CODE);
275 add_event_entry(i);
John Levon0c0a4002005-06-23 22:02:47 -0700276 last_cookie = INVALID_COOKIE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700277}
278
279static void add_kernel_ctx_switch(unsigned int in_kernel)
280{
281 add_event_entry(ESCAPE_CODE);
282 if (in_kernel)
283 add_event_entry(KERNEL_ENTER_SWITCH_CODE);
284 else
285 add_event_entry(KERNEL_EXIT_SWITCH_CODE);
286}
287
288static void
289add_user_ctx_switch(struct task_struct const * task, unsigned long cookie)
290{
291 add_event_entry(ESCAPE_CODE);
292 add_event_entry(CTX_SWITCH_CODE);
293 add_event_entry(task->pid);
294 add_event_entry(cookie);
295 /* Another code for daemon back-compat */
296 add_event_entry(ESCAPE_CODE);
297 add_event_entry(CTX_TGID_CODE);
298 add_event_entry(task->tgid);
299}
300
301
302static void add_cookie_switch(unsigned long cookie)
303{
304 add_event_entry(ESCAPE_CODE);
305 add_event_entry(COOKIE_SWITCH_CODE);
306 add_event_entry(cookie);
307}
308
309
310static void add_trace_begin(void)
311{
312 add_event_entry(ESCAPE_CODE);
313 add_event_entry(TRACE_BEGIN_CODE);
314}
315
316
317static void add_sample_entry(unsigned long offset, unsigned long event)
318{
319 add_event_entry(offset);
320 add_event_entry(event);
321}
322
323
324static int add_us_sample(struct mm_struct * mm, struct op_sample * s)
325{
326 unsigned long cookie;
327 off_t offset;
328
329 cookie = lookup_dcookie(mm, s->eip, &offset);
330
John Levon0c0a4002005-06-23 22:02:47 -0700331 if (cookie == INVALID_COOKIE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700332 atomic_inc(&oprofile_stats.sample_lost_no_mapping);
333 return 0;
334 }
335
336 if (cookie != last_cookie) {
337 add_cookie_switch(cookie);
338 last_cookie = cookie;
339 }
340
341 add_sample_entry(offset, s->event);
342
343 return 1;
344}
345
346
347/* Add a sample to the global event buffer. If possible the
348 * sample is converted into a persistent dentry/offset pair
349 * for later lookup from userspace.
350 */
351static int
352add_sample(struct mm_struct * mm, struct op_sample * s, int in_kernel)
353{
354 if (in_kernel) {
355 add_sample_entry(s->eip, s->event);
356 return 1;
357 } else if (mm) {
358 return add_us_sample(mm, s);
359 } else {
360 atomic_inc(&oprofile_stats.sample_lost_no_mm);
361 }
362 return 0;
363}
364
365
366static void release_mm(struct mm_struct * mm)
367{
368 if (!mm)
369 return;
370 up_read(&mm->mmap_sem);
371 mmput(mm);
372}
373
374
375static struct mm_struct * take_tasks_mm(struct task_struct * task)
376{
377 struct mm_struct * mm = get_task_mm(task);
378 if (mm)
379 down_read(&mm->mmap_sem);
380 return mm;
381}
382
383
384static inline int is_code(unsigned long val)
385{
386 return val == ESCAPE_CODE;
387}
388
389
390/* "acquire" as many cpu buffer slots as we can */
391static unsigned long get_slots(struct oprofile_cpu_buffer * b)
392{
393 unsigned long head = b->head_pos;
394 unsigned long tail = b->tail_pos;
395
396 /*
397 * Subtle. This resets the persistent last_task
398 * and in_kernel values used for switching notes.
399 * BUT, there is a small window between reading
400 * head_pos, and this call, that means samples
401 * can appear at the new head position, but not
402 * be prefixed with the notes for switching
403 * kernel mode or a task switch. This small hole
404 * can lead to mis-attribution or samples where
405 * we don't know if it's in the kernel or not,
406 * at the start of an event buffer.
407 */
408 cpu_buffer_reset(b);
409
410 if (head >= tail)
411 return head - tail;
412
413 return head + (b->buffer_size - tail);
414}
415
416
417static void increment_tail(struct oprofile_cpu_buffer * b)
418{
419 unsigned long new_tail = b->tail_pos + 1;
420
421 rmb();
422
423 if (new_tail < b->buffer_size)
424 b->tail_pos = new_tail;
425 else
426 b->tail_pos = 0;
427}
428
429
430/* Move tasks along towards death. Any tasks on dead_tasks
431 * will definitely have no remaining references in any
432 * CPU buffers at this point, because we use two lists,
433 * and to have reached the list, it must have gone through
434 * one full sync already.
435 */
436static void process_task_mortuary(void)
437{
Paul E. McKenney4369ef32006-01-08 01:01:35 -0800438 unsigned long flags;
439 LIST_HEAD(local_dead_tasks);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700440 struct task_struct * task;
Paul E. McKenney4369ef32006-01-08 01:01:35 -0800441 struct task_struct * ttask;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700442
Paul E. McKenney4369ef32006-01-08 01:01:35 -0800443 spin_lock_irqsave(&task_mortuary, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700444
Paul E. McKenney4369ef32006-01-08 01:01:35 -0800445 list_splice_init(&dead_tasks, &local_dead_tasks);
446 list_splice_init(&dying_tasks, &dead_tasks);
447
448 spin_unlock_irqrestore(&task_mortuary, flags);
449
450 list_for_each_entry_safe(task, ttask, &local_dead_tasks, tasks) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700451 list_del(&task->tasks);
452 free_task(task);
453 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700454}
455
456
457static void mark_done(int cpu)
458{
459 int i;
460
461 cpu_set(cpu, marked_cpus);
462
463 for_each_online_cpu(i) {
464 if (!cpu_isset(i, marked_cpus))
465 return;
466 }
467
468 /* All CPUs have been processed at least once,
469 * we can process the mortuary once
470 */
471 process_task_mortuary();
472
473 cpus_clear(marked_cpus);
474}
475
476
477/* FIXME: this is not sufficient if we implement syscall barrier backtrace
478 * traversal, the code switch to sb_sample_start at first kernel enter/exit
479 * switch so we need a fifth state and some special handling in sync_buffer()
480 */
481typedef enum {
482 sb_bt_ignore = -2,
483 sb_buffer_start,
484 sb_bt_start,
485 sb_sample_start,
486} sync_buffer_state;
487
488/* Sync one of the CPU's buffers into the global event buffer.
489 * Here we need to go through each batch of samples punctuated
490 * by context switch notes, taking the task's mmap_sem and doing
491 * lookup in task->mm->mmap to convert EIP into dcookie/offset
492 * value.
493 */
494void sync_buffer(int cpu)
495{
496 struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[cpu];
497 struct mm_struct *mm = NULL;
498 struct task_struct * new;
499 unsigned long cookie = 0;
500 int in_kernel = 1;
501 unsigned int i;
502 sync_buffer_state state = sb_buffer_start;
503 unsigned long available;
504
Markus Armbruster59cc1852006-06-25 05:47:33 -0700505 mutex_lock(&buffer_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506
507 add_cpu_switch(cpu);
508
509 /* Remember, only we can modify tail_pos */
510
511 available = get_slots(cpu_buf);
512
513 for (i = 0; i < available; ++i) {
514 struct op_sample * s = &cpu_buf->buffer[cpu_buf->tail_pos];
515
516 if (is_code(s->eip)) {
517 if (s->event <= CPU_IS_KERNEL) {
518 /* kernel/userspace switch */
519 in_kernel = s->event;
520 if (state == sb_buffer_start)
521 state = sb_sample_start;
522 add_kernel_ctx_switch(s->event);
523 } else if (s->event == CPU_TRACE_BEGIN) {
524 state = sb_bt_start;
525 add_trace_begin();
526 } else {
527 struct mm_struct * oldmm = mm;
528
529 /* userspace context switch */
530 new = (struct task_struct *)s->event;
531
532 release_mm(oldmm);
533 mm = take_tasks_mm(new);
534 if (mm != oldmm)
535 cookie = get_exec_dcookie(mm);
536 add_user_ctx_switch(new, cookie);
537 }
538 } else {
539 if (state >= sb_bt_start &&
540 !add_sample(mm, s, in_kernel)) {
541 if (state == sb_bt_start) {
542 state = sb_bt_ignore;
543 atomic_inc(&oprofile_stats.bt_lost_no_mapping);
544 }
545 }
546 }
547
548 increment_tail(cpu_buf);
549 }
550 release_mm(mm);
551
552 mark_done(cpu);
553
Markus Armbruster59cc1852006-06-25 05:47:33 -0700554 mutex_unlock(&buffer_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700555}