ia64/linux-2.6.18-xen.hg

view drivers/oprofile/buffer_sync.c @ 0:831230e53067

Import 2.6.18 from kernel.org tarball.
author Ian Campbell <ian.campbell@xensource.com>
date Wed Apr 11 14:15:44 2007 +0100 (2007-04-11)
parents
children 132f24200f4c
line source
1 /**
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 */
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>
30 #include "oprofile_stats.h"
31 #include "event_buffer.h"
32 #include "cpu_buffer.h"
33 #include "buffer_sync.h"
35 static LIST_HEAD(dying_tasks);
36 static LIST_HEAD(dead_tasks);
37 static cpumask_t marked_cpus = CPU_MASK_NONE;
38 static DEFINE_SPINLOCK(task_mortuary);
39 static void process_task_mortuary(void);
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 * Can be invoked from softirq via RCU callback due to
47 * call_rcu() of the task struct, hence the _irqsave.
48 */
49 static int task_free_notify(struct notifier_block * self, unsigned long val, void * data)
50 {
51 unsigned long flags;
52 struct task_struct * task = data;
53 spin_lock_irqsave(&task_mortuary, flags);
54 list_add(&task->tasks, &dying_tasks);
55 spin_unlock_irqrestore(&task_mortuary, flags);
56 return NOTIFY_OK;
57 }
60 /* The task is on its way out. A sync of the buffer means we can catch
61 * any remaining samples for this task.
62 */
63 static int task_exit_notify(struct notifier_block * self, unsigned long val, void * data)
64 {
65 /* To avoid latency problems, we only process the current CPU,
66 * hoping that most samples for the task are on this CPU
67 */
68 sync_buffer(raw_smp_processor_id());
69 return 0;
70 }
73 /* The task is about to try a do_munmap(). We peek at what it's going to
74 * do, and if it's an executable region, process the samples first, so
75 * we don't lose any. This does not have to be exact, it's a QoI issue
76 * only.
77 */
78 static int munmap_notify(struct notifier_block * self, unsigned long val, void * data)
79 {
80 unsigned long addr = (unsigned long)data;
81 struct mm_struct * mm = current->mm;
82 struct vm_area_struct * mpnt;
84 down_read(&mm->mmap_sem);
86 mpnt = find_vma(mm, addr);
87 if (mpnt && mpnt->vm_file && (mpnt->vm_flags & VM_EXEC)) {
88 up_read(&mm->mmap_sem);
89 /* To avoid latency problems, we only process the current CPU,
90 * hoping that most samples for the task are on this CPU
91 */
92 sync_buffer(raw_smp_processor_id());
93 return 0;
94 }
96 up_read(&mm->mmap_sem);
97 return 0;
98 }
101 /* We need to be told about new modules so we don't attribute to a previously
102 * loaded module, or drop the samples on the floor.
103 */
104 static int module_load_notify(struct notifier_block * self, unsigned long val, void * data)
105 {
106 #ifdef CONFIG_MODULES
107 if (val != MODULE_STATE_COMING)
108 return 0;
110 /* FIXME: should we process all CPU buffers ? */
111 mutex_lock(&buffer_mutex);
112 add_event_entry(ESCAPE_CODE);
113 add_event_entry(MODULE_LOADED_CODE);
114 mutex_unlock(&buffer_mutex);
115 #endif
116 return 0;
117 }
120 static struct notifier_block task_free_nb = {
121 .notifier_call = task_free_notify,
122 };
124 static struct notifier_block task_exit_nb = {
125 .notifier_call = task_exit_notify,
126 };
128 static struct notifier_block munmap_nb = {
129 .notifier_call = munmap_notify,
130 };
132 static struct notifier_block module_load_nb = {
133 .notifier_call = module_load_notify,
134 };
137 static void end_sync(void)
138 {
139 end_cpu_work();
140 /* make sure we don't leak task structs */
141 process_task_mortuary();
142 process_task_mortuary();
143 }
146 int sync_start(void)
147 {
148 int err;
150 start_cpu_work();
152 err = task_handoff_register(&task_free_nb);
153 if (err)
154 goto out1;
155 err = profile_event_register(PROFILE_TASK_EXIT, &task_exit_nb);
156 if (err)
157 goto out2;
158 err = profile_event_register(PROFILE_MUNMAP, &munmap_nb);
159 if (err)
160 goto out3;
161 err = register_module_notifier(&module_load_nb);
162 if (err)
163 goto out4;
165 out:
166 return err;
167 out4:
168 profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
169 out3:
170 profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
171 out2:
172 task_handoff_unregister(&task_free_nb);
173 out1:
174 end_sync();
175 goto out;
176 }
179 void sync_stop(void)
180 {
181 unregister_module_notifier(&module_load_nb);
182 profile_event_unregister(PROFILE_MUNMAP, &munmap_nb);
183 profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb);
184 task_handoff_unregister(&task_free_nb);
185 end_sync();
186 }
189 /* Optimisation. We can manage without taking the dcookie sem
190 * because we cannot reach this code without at least one
191 * dcookie user still being registered (namely, the reader
192 * of the event buffer). */
193 static inline unsigned long fast_get_dcookie(struct dentry * dentry,
194 struct vfsmount * vfsmnt)
195 {
196 unsigned long cookie;
198 if (dentry->d_cookie)
199 return (unsigned long)dentry;
200 get_dcookie(dentry, vfsmnt, &cookie);
201 return cookie;
202 }
205 /* Look up the dcookie for the task's first VM_EXECUTABLE mapping,
206 * which corresponds loosely to "application name". This is
207 * not strictly necessary but allows oprofile to associate
208 * shared-library samples with particular applications
209 */
210 static unsigned long get_exec_dcookie(struct mm_struct * mm)
211 {
212 unsigned long cookie = NO_COOKIE;
213 struct vm_area_struct * vma;
215 if (!mm)
216 goto out;
218 for (vma = mm->mmap; vma; vma = vma->vm_next) {
219 if (!vma->vm_file)
220 continue;
221 if (!(vma->vm_flags & VM_EXECUTABLE))
222 continue;
223 cookie = fast_get_dcookie(vma->vm_file->f_dentry,
224 vma->vm_file->f_vfsmnt);
225 break;
226 }
228 out:
229 return cookie;
230 }
233 /* Convert the EIP value of a sample into a persistent dentry/offset
234 * pair that can then be added to the global event buffer. We make
235 * sure to do this lookup before a mm->mmap modification happens so
236 * we don't lose track.
237 */
238 static unsigned long lookup_dcookie(struct mm_struct * mm, unsigned long addr, off_t * offset)
239 {
240 unsigned long cookie = NO_COOKIE;
241 struct vm_area_struct * vma;
243 for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
245 if (addr < vma->vm_start || addr >= vma->vm_end)
246 continue;
248 if (vma->vm_file) {
249 cookie = fast_get_dcookie(vma->vm_file->f_dentry,
250 vma->vm_file->f_vfsmnt);
251 *offset = (vma->vm_pgoff << PAGE_SHIFT) + addr -
252 vma->vm_start;
253 } else {
254 /* must be an anonymous map */
255 *offset = addr;
256 }
258 break;
259 }
261 if (!vma)
262 cookie = INVALID_COOKIE;
264 return cookie;
265 }
268 static unsigned long last_cookie = INVALID_COOKIE;
270 static void add_cpu_switch(int i)
271 {
272 add_event_entry(ESCAPE_CODE);
273 add_event_entry(CPU_SWITCH_CODE);
274 add_event_entry(i);
275 last_cookie = INVALID_COOKIE;
276 }
278 static void add_kernel_ctx_switch(unsigned int in_kernel)
279 {
280 add_event_entry(ESCAPE_CODE);
281 if (in_kernel)
282 add_event_entry(KERNEL_ENTER_SWITCH_CODE);
283 else
284 add_event_entry(KERNEL_EXIT_SWITCH_CODE);
285 }
287 static void
288 add_user_ctx_switch(struct task_struct const * task, unsigned long cookie)
289 {
290 add_event_entry(ESCAPE_CODE);
291 add_event_entry(CTX_SWITCH_CODE);
292 add_event_entry(task->pid);
293 add_event_entry(cookie);
294 /* Another code for daemon back-compat */
295 add_event_entry(ESCAPE_CODE);
296 add_event_entry(CTX_TGID_CODE);
297 add_event_entry(task->tgid);
298 }
301 static void add_cookie_switch(unsigned long cookie)
302 {
303 add_event_entry(ESCAPE_CODE);
304 add_event_entry(COOKIE_SWITCH_CODE);
305 add_event_entry(cookie);
306 }
309 static void add_trace_begin(void)
310 {
311 add_event_entry(ESCAPE_CODE);
312 add_event_entry(TRACE_BEGIN_CODE);
313 }
316 static void add_sample_entry(unsigned long offset, unsigned long event)
317 {
318 add_event_entry(offset);
319 add_event_entry(event);
320 }
323 static int add_us_sample(struct mm_struct * mm, struct op_sample * s)
324 {
325 unsigned long cookie;
326 off_t offset;
328 cookie = lookup_dcookie(mm, s->eip, &offset);
330 if (cookie == INVALID_COOKIE) {
331 atomic_inc(&oprofile_stats.sample_lost_no_mapping);
332 return 0;
333 }
335 if (cookie != last_cookie) {
336 add_cookie_switch(cookie);
337 last_cookie = cookie;
338 }
340 add_sample_entry(offset, s->event);
342 return 1;
343 }
346 /* Add a sample to the global event buffer. If possible the
347 * sample is converted into a persistent dentry/offset pair
348 * for later lookup from userspace.
349 */
350 static int
351 add_sample(struct mm_struct * mm, struct op_sample * s, int in_kernel)
352 {
353 if (in_kernel) {
354 add_sample_entry(s->eip, s->event);
355 return 1;
356 } else if (mm) {
357 return add_us_sample(mm, s);
358 } else {
359 atomic_inc(&oprofile_stats.sample_lost_no_mm);
360 }
361 return 0;
362 }
365 static void release_mm(struct mm_struct * mm)
366 {
367 if (!mm)
368 return;
369 up_read(&mm->mmap_sem);
370 mmput(mm);
371 }
374 static struct mm_struct * take_tasks_mm(struct task_struct * task)
375 {
376 struct mm_struct * mm = get_task_mm(task);
377 if (mm)
378 down_read(&mm->mmap_sem);
379 return mm;
380 }
383 static inline int is_code(unsigned long val)
384 {
385 return val == ESCAPE_CODE;
386 }
389 /* "acquire" as many cpu buffer slots as we can */
390 static unsigned long get_slots(struct oprofile_cpu_buffer * b)
391 {
392 unsigned long head = b->head_pos;
393 unsigned long tail = b->tail_pos;
395 /*
396 * Subtle. This resets the persistent last_task
397 * and in_kernel values used for switching notes.
398 * BUT, there is a small window between reading
399 * head_pos, and this call, that means samples
400 * can appear at the new head position, but not
401 * be prefixed with the notes for switching
402 * kernel mode or a task switch. This small hole
403 * can lead to mis-attribution or samples where
404 * we don't know if it's in the kernel or not,
405 * at the start of an event buffer.
406 */
407 cpu_buffer_reset(b);
409 if (head >= tail)
410 return head - tail;
412 return head + (b->buffer_size - tail);
413 }
416 static void increment_tail(struct oprofile_cpu_buffer * b)
417 {
418 unsigned long new_tail = b->tail_pos + 1;
420 rmb();
422 if (new_tail < b->buffer_size)
423 b->tail_pos = new_tail;
424 else
425 b->tail_pos = 0;
426 }
429 /* Move tasks along towards death. Any tasks on dead_tasks
430 * will definitely have no remaining references in any
431 * CPU buffers at this point, because we use two lists,
432 * and to have reached the list, it must have gone through
433 * one full sync already.
434 */
435 static void process_task_mortuary(void)
436 {
437 unsigned long flags;
438 LIST_HEAD(local_dead_tasks);
439 struct task_struct * task;
440 struct task_struct * ttask;
442 spin_lock_irqsave(&task_mortuary, flags);
444 list_splice_init(&dead_tasks, &local_dead_tasks);
445 list_splice_init(&dying_tasks, &dead_tasks);
447 spin_unlock_irqrestore(&task_mortuary, flags);
449 list_for_each_entry_safe(task, ttask, &local_dead_tasks, tasks) {
450 list_del(&task->tasks);
451 free_task(task);
452 }
453 }
456 static void mark_done(int cpu)
457 {
458 int i;
460 cpu_set(cpu, marked_cpus);
462 for_each_online_cpu(i) {
463 if (!cpu_isset(i, marked_cpus))
464 return;
465 }
467 /* All CPUs have been processed at least once,
468 * we can process the mortuary once
469 */
470 process_task_mortuary();
472 cpus_clear(marked_cpus);
473 }
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 */
480 typedef enum {
481 sb_bt_ignore = -2,
482 sb_buffer_start,
483 sb_bt_start,
484 sb_sample_start,
485 } sync_buffer_state;
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 */
493 void 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;
504 mutex_lock(&buffer_mutex);
506 add_cpu_switch(cpu);
508 /* Remember, only we can modify tail_pos */
510 available = get_slots(cpu_buf);
512 for (i = 0; i < available; ++i) {
513 struct op_sample * s = &cpu_buf->buffer[cpu_buf->tail_pos];
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;
528 /* userspace context switch */
529 new = (struct task_struct *)s->event;
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 }
547 increment_tail(cpu_buf);
548 }
549 release_mm(mm);
551 mark_done(cpu);
553 mutex_unlock(&buffer_mutex);
554 }