blob: 531b0731314162e4afea759d8e52ada9bb11a1f8 [file] [log] [blame]
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>
29
30#include "oprofile_stats.h"
31#include "event_buffer.h"
32#include "cpu_buffer.h"
33#include "buffer_sync.h"
34
35static LIST_HEAD(dying_tasks);
36static LIST_HEAD(dead_tasks);
37static cpumask_t marked_cpus = CPU_MASK_NONE;
38static DEFINE_SPINLOCK(task_mortuary);
39static void process_task_mortuary(void);
40
41
42/* Take ownership of the task struct and place it on the
43 * list for processing. Only after two full buffer syncs
44 * does the task eventually get freed, because by then
45 * we are sure we will not reference it again.
46 */
47static int task_free_notify(struct notifier_block * self, unsigned long val, void * data)
48{
49 struct task_struct * task = data;
50 spin_lock(&task_mortuary);
51 list_add(&task->tasks, &dying_tasks);
52 spin_unlock(&task_mortuary);
53 return NOTIFY_OK;
54}
55
56
57/* The task is on its way out. A sync of the buffer means we can catch
58 * any remaining samples for this task.
59 */
60static int task_exit_notify(struct notifier_block * self, unsigned long val, void * data)
61{
62 /* To avoid latency problems, we only process the current CPU,
63 * hoping that most samples for the task are on this CPU
64 */
Ingo Molnar39c715b2005-06-21 17:14:34 -070065 sync_buffer(raw_smp_processor_id());
Linus Torvalds1da177e2005-04-16 15:20:36 -070066 return 0;
67}
68
69
70/* The task is about to try a do_munmap(). We peek at what it's going to
71 * do, and if it's an executable region, process the samples first, so
72 * we don't lose any. This does not have to be exact, it's a QoI issue
73 * only.
74 */
75static int munmap_notify(struct notifier_block * self, unsigned long val, void * data)
76{
77 unsigned long addr = (unsigned long)data;
78 struct mm_struct * mm = current->mm;
79 struct vm_area_struct * mpnt;
80
81 down_read(&mm->mmap_sem);
82
83 mpnt = find_vma(mm, addr);
84 if (mpnt && mpnt->vm_file && (mpnt->vm_flags & VM_EXEC)) {
85 up_read(&mm->mmap_sem);
86 /* To avoid latency problems, we only process the current CPU,
87 * hoping that most samples for the task are on this CPU
88 */
Ingo Molnar39c715b2005-06-21 17:14:34 -070089 sync_buffer(raw_smp_processor_id());
Linus Torvalds1da177e2005-04-16 15:20:36 -070090 return 0;
91 }
92
93 up_read(&mm->mmap_sem);
94 return 0;
95}
96
97
98/* We need to be told about new modules so we don't attribute to a previously
99 * loaded module, or drop the samples on the floor.
100 */
101static int module_load_notify(struct notifier_block * self, unsigned long val, void * data)
102{
103#ifdef CONFIG_MODULES
104 if (val != MODULE_STATE_COMING)
105 return 0;
106
107 /* FIXME: should we process all CPU buffers ? */
108 down(&buffer_sem);
109 add_event_entry(ESCAPE_CODE);
110 add_event_entry(MODULE_LOADED_CODE);
111 up(&buffer_sem);
112#endif
113 return 0;
114}
115
116
117static struct notifier_block task_free_nb = {
118 .notifier_call = task_free_notify,
119};
120
121static struct notifier_block task_exit_nb = {
122 .notifier_call = task_exit_notify,
123};
124
125static struct notifier_block munmap_nb = {
126 .notifier_call = munmap_notify,
127};
128
129static struct notifier_block module_load_nb = {
130 .notifier_call = module_load_notify,
131};
132
133
134static void end_sync(void)
135{
136 end_cpu_work();
137 /* make sure we don't leak task structs */
138 process_task_mortuary();
139 process_task_mortuary();
140}
141
142
143int sync_start(void)
144{
145 int err;
146
147 start_cpu_work();
148
149 err = task_handoff_register(&task_free_nb);
150 if (err)
151 goto out1;
152 err = profile_event_register(PROFILE_TASK_EXIT, &task_exit_nb);
153 if (err)
154 goto out2;
155 err = profile_event_register(PROFILE_MUNMAP, &munmap_nb);
156 if (err)
157 goto out3;
158 err = register_module_notifier(&module_load_nb);
159 if (err)
160 goto out4;
161
162out:
163 return err;
164out4:
165 profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
166out3:
167 profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
168out2:
169 task_handoff_unregister(&task_free_nb);
170out1:
171 end_sync();
172 goto out;
173}
174
175
176void sync_stop(void)
177{
178 unregister_module_notifier(&module_load_nb);
179 profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
180 profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
181 task_handoff_unregister(&task_free_nb);
182 end_sync();
183}
184
185
186/* Optimisation. We can manage without taking the dcookie sem
187 * because we cannot reach this code without at least one
188 * dcookie user still being registered (namely, the reader
189 * of the event buffer). */
190static inline unsigned long fast_get_dcookie(struct dentry * dentry,
191 struct vfsmount * vfsmnt)
192{
193 unsigned long cookie;
194
195 if (dentry->d_cookie)
196 return (unsigned long)dentry;
197 get_dcookie(dentry, vfsmnt, &cookie);
198 return cookie;
199}
200
201
202/* Look up the dcookie for the task's first VM_EXECUTABLE mapping,
203 * which corresponds loosely to "application name". This is
204 * not strictly necessary but allows oprofile to associate
205 * shared-library samples with particular applications
206 */
207static unsigned long get_exec_dcookie(struct mm_struct * mm)
208{
John Levon0c0a4002005-06-23 22:02:47 -0700209 unsigned long cookie = NO_COOKIE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700210 struct vm_area_struct * vma;
211
212 if (!mm)
213 goto out;
214
215 for (vma = mm->mmap; vma; vma = vma->vm_next) {
216 if (!vma->vm_file)
217 continue;
218 if (!(vma->vm_flags & VM_EXECUTABLE))
219 continue;
220 cookie = fast_get_dcookie(vma->vm_file->f_dentry,
221 vma->vm_file->f_vfsmnt);
222 break;
223 }
224
225out:
226 return cookie;
227}
228
229
230/* Convert the EIP value of a sample into a persistent dentry/offset
231 * pair that can then be added to the global event buffer. We make
232 * sure to do this lookup before a mm->mmap modification happens so
233 * we don't lose track.
234 */
235static unsigned long lookup_dcookie(struct mm_struct * mm, unsigned long addr, off_t * offset)
236{
John Levon0c0a4002005-06-23 22:02:47 -0700237 unsigned long cookie = NO_COOKIE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700238 struct vm_area_struct * vma;
239
240 for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
241
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242 if (addr < vma->vm_start || addr >= vma->vm_end)
243 continue;
244
John Levon0c0a4002005-06-23 22:02:47 -0700245 if (vma->vm_file) {
246 cookie = fast_get_dcookie(vma->vm_file->f_dentry,
247 vma->vm_file->f_vfsmnt);
248 *offset = (vma->vm_pgoff << PAGE_SHIFT) + addr -
249 vma->vm_start;
250 } else {
251 /* must be an anonymous map */
252 *offset = addr;
253 }
254
Linus Torvalds1da177e2005-04-16 15:20:36 -0700255 break;
256 }
257
John Levon0c0a4002005-06-23 22:02:47 -0700258 if (!vma)
259 cookie = INVALID_COOKIE;
260
Linus Torvalds1da177e2005-04-16 15:20:36 -0700261 return cookie;
262}
263
264
John Levon0c0a4002005-06-23 22:02:47 -0700265static unsigned long last_cookie = INVALID_COOKIE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266
267static void add_cpu_switch(int i)
268{
269 add_event_entry(ESCAPE_CODE);
270 add_event_entry(CPU_SWITCH_CODE);
271 add_event_entry(i);
John Levon0c0a4002005-06-23 22:02:47 -0700272 last_cookie = INVALID_COOKIE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700273}
274
275static void add_kernel_ctx_switch(unsigned int in_kernel)
276{
277 add_event_entry(ESCAPE_CODE);
278 if (in_kernel)
279 add_event_entry(KERNEL_ENTER_SWITCH_CODE);
280 else
281 add_event_entry(KERNEL_EXIT_SWITCH_CODE);
282}
283
284static void
285add_user_ctx_switch(struct task_struct const * task, unsigned long cookie)
286{
287 add_event_entry(ESCAPE_CODE);
288 add_event_entry(CTX_SWITCH_CODE);
289 add_event_entry(task->pid);
290 add_event_entry(cookie);
291 /* Another code for daemon back-compat */
292 add_event_entry(ESCAPE_CODE);
293 add_event_entry(CTX_TGID_CODE);
294 add_event_entry(task->tgid);
295}
296
297
298static void add_cookie_switch(unsigned long cookie)
299{
300 add_event_entry(ESCAPE_CODE);
301 add_event_entry(COOKIE_SWITCH_CODE);
302 add_event_entry(cookie);
303}
304
305
306static void add_trace_begin(void)
307{
308 add_event_entry(ESCAPE_CODE);
309 add_event_entry(TRACE_BEGIN_CODE);
310}
311
312
313static void add_sample_entry(unsigned long offset, unsigned long event)
314{
315 add_event_entry(offset);
316 add_event_entry(event);
317}
318
319
320static int add_us_sample(struct mm_struct * mm, struct op_sample * s)
321{
322 unsigned long cookie;
323 off_t offset;
324
325 cookie = lookup_dcookie(mm, s->eip, &offset);
326
John Levon0c0a4002005-06-23 22:02:47 -0700327 if (cookie == INVALID_COOKIE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700328 atomic_inc(&oprofile_stats.sample_lost_no_mapping);
329 return 0;
330 }
331
332 if (cookie != last_cookie) {
333 add_cookie_switch(cookie);
334 last_cookie = cookie;
335 }
336
337 add_sample_entry(offset, s->event);
338
339 return 1;
340}
341
342
343/* Add a sample to the global event buffer. If possible the
344 * sample is converted into a persistent dentry/offset pair
345 * for later lookup from userspace.
346 */
347static int
348add_sample(struct mm_struct * mm, struct op_sample * s, int in_kernel)
349{
350 if (in_kernel) {
351 add_sample_entry(s->eip, s->event);
352 return 1;
353 } else if (mm) {
354 return add_us_sample(mm, s);
355 } else {
356 atomic_inc(&oprofile_stats.sample_lost_no_mm);
357 }
358 return 0;
359}
360
361
362static void release_mm(struct mm_struct * mm)
363{
364 if (!mm)
365 return;
366 up_read(&mm->mmap_sem);
367 mmput(mm);
368}
369
370
371static struct mm_struct * take_tasks_mm(struct task_struct * task)
372{
373 struct mm_struct * mm = get_task_mm(task);
374 if (mm)
375 down_read(&mm->mmap_sem);
376 return mm;
377}
378
379
380static inline int is_code(unsigned long val)
381{
382 return val == ESCAPE_CODE;
383}
384
385
386/* "acquire" as many cpu buffer slots as we can */
387static unsigned long get_slots(struct oprofile_cpu_buffer * b)
388{
389 unsigned long head = b->head_pos;
390 unsigned long tail = b->tail_pos;
391
392 /*
393 * Subtle. This resets the persistent last_task
394 * and in_kernel values used for switching notes.
395 * BUT, there is a small window between reading
396 * head_pos, and this call, that means samples
397 * can appear at the new head position, but not
398 * be prefixed with the notes for switching
399 * kernel mode or a task switch. This small hole
400 * can lead to mis-attribution or samples where
401 * we don't know if it's in the kernel or not,
402 * at the start of an event buffer.
403 */
404 cpu_buffer_reset(b);
405
406 if (head >= tail)
407 return head - tail;
408
409 return head + (b->buffer_size - tail);
410}
411
412
413static void increment_tail(struct oprofile_cpu_buffer * b)
414{
415 unsigned long new_tail = b->tail_pos + 1;
416
417 rmb();
418
419 if (new_tail < b->buffer_size)
420 b->tail_pos = new_tail;
421 else
422 b->tail_pos = 0;
423}
424
425
426/* Move tasks along towards death. Any tasks on dead_tasks
427 * will definitely have no remaining references in any
428 * CPU buffers at this point, because we use two lists,
429 * and to have reached the list, it must have gone through
430 * one full sync already.
431 */
432static void process_task_mortuary(void)
433{
434 struct list_head * pos;
435 struct list_head * pos2;
436 struct task_struct * task;
437
438 spin_lock(&task_mortuary);
439
440 list_for_each_safe(pos, pos2, &dead_tasks) {
441 task = list_entry(pos, struct task_struct, tasks);
442 list_del(&task->tasks);
443 free_task(task);
444 }
445
446 list_for_each_safe(pos, pos2, &dying_tasks) {
447 task = list_entry(pos, struct task_struct, tasks);
448 list_del(&task->tasks);
449 list_add_tail(&task->tasks, &dead_tasks);
450 }
451
452 spin_unlock(&task_mortuary);
453}
454
455
456static void mark_done(int cpu)
457{
458 int i;
459
460 cpu_set(cpu, marked_cpus);
461
462 for_each_online_cpu(i) {
463 if (!cpu_isset(i, marked_cpus))
464 return;
465 }
466
467 /* All CPUs have been processed at least once,
468 * we can process the mortuary once
469 */
470 process_task_mortuary();
471
472 cpus_clear(marked_cpus);
473}
474
475
476/* FIXME: this is not sufficient if we implement syscall barrier backtrace
477 * traversal, the code switch to sb_sample_start at first kernel enter/exit
478 * switch so we need a fifth state and some special handling in sync_buffer()
479 */
480typedef enum {
481 sb_bt_ignore = -2,
482 sb_buffer_start,
483 sb_bt_start,
484 sb_sample_start,
485} sync_buffer_state;
486
487/* Sync one of the CPU's buffers into the global event buffer.
488 * Here we need to go through each batch of samples punctuated
489 * by context switch notes, taking the task's mmap_sem and doing
490 * lookup in task->mm->mmap to convert EIP into dcookie/offset
491 * value.
492 */
493void sync_buffer(int cpu)
494{
495 struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[cpu];
496 struct mm_struct *mm = NULL;
497 struct task_struct * new;
498 unsigned long cookie = 0;
499 int in_kernel = 1;
500 unsigned int i;
501 sync_buffer_state state = sb_buffer_start;
502 unsigned long available;
503
504 down(&buffer_sem);
505
506 add_cpu_switch(cpu);
507
508 /* Remember, only we can modify tail_pos */
509
510 available = get_slots(cpu_buf);
511
512 for (i = 0; i < available; ++i) {
513 struct op_sample * s = &cpu_buf->buffer[cpu_buf->tail_pos];
514
515 if (is_code(s->eip)) {
516 if (s->event <= CPU_IS_KERNEL) {
517 /* kernel/userspace switch */
518 in_kernel = s->event;
519 if (state == sb_buffer_start)
520 state = sb_sample_start;
521 add_kernel_ctx_switch(s->event);
522 } else if (s->event == CPU_TRACE_BEGIN) {
523 state = sb_bt_start;
524 add_trace_begin();
525 } else {
526 struct mm_struct * oldmm = mm;
527
528 /* userspace context switch */
529 new = (struct task_struct *)s->event;
530
531 release_mm(oldmm);
532 mm = take_tasks_mm(new);
533 if (mm != oldmm)
534 cookie = get_exec_dcookie(mm);
535 add_user_ctx_switch(new, cookie);
536 }
537 } else {
538 if (state >= sb_bt_start &&
539 !add_sample(mm, s, in_kernel)) {
540 if (state == sb_bt_start) {
541 state = sb_bt_ignore;
542 atomic_inc(&oprofile_stats.bt_lost_no_mapping);
543 }
544 }
545 }
546
547 increment_tail(cpu_buf);
548 }
549 release_mm(mm);
550
551 mark_done(cpu);
552
553 up(&buffer_sem);
554}