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authorLi Zefan <lizf@cn.fujitsu.com>2009-05-05 22:33:45 -0400
committerIngo Molnar <mingo@elte.hu>2009-05-06 04:38:19 -0400
commit20c8928abe70e204bd077ab6cfe23002d7788983 (patch)
treee161656f99c814ebdd69df8b5a79dab58f80065e /kernel/trace
parent2df75e415709ad12862028916c772c1f377f6a7c (diff)
tracing/events: fix concurrent access to ftrace_events list
A module will add/remove its trace events when it gets loaded/unloaded, so the ftrace_events list is not "const", and concurrent access needs to be protected. This patch thus fixes races between loading/unloding modules and read 'available_events' or read/write 'set_event', etc. Below shows how to reproduce the race: # for ((; ;)) { cat /mnt/tracing/available_events; } > /dev/null & # for ((; ;)) { insmod trace-events-sample.ko; rmmod sample; } & After a while: BUG: unable to handle kernel paging request at 0010011c IP: [<c1080f27>] t_next+0x1b/0x2d ... Call Trace: [<c10c90e6>] ? seq_read+0x217/0x30d [<c10c8ecf>] ? seq_read+0x0/0x30d [<c10b4c19>] ? vfs_read+0x8f/0x136 [<c10b4fc3>] ? sys_read+0x40/0x65 [<c1002a68>] ? sysenter_do_call+0x12/0x36 [ Impact: fix races when concurrent accessing ftrace_events list ] Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Tom Zanussi <tzanussi@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <4A00F709.3080800@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/trace.h1
-rw-r--r--kernel/trace/trace_event_profile.c19
-rw-r--r--kernel/trace/trace_events.c20
-rw-r--r--kernel/trace/trace_events_filter.c10
4 files changed, 33 insertions, 17 deletions
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 7736fe8c1b76..777c6c3a0cde 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -825,6 +825,7 @@ static int filter_pred_##size(struct filter_pred *pred, void *event, \
825 return match; \ 825 return match; \
826} 826}
827 827
828extern struct mutex event_mutex;
828extern struct list_head ftrace_events; 829extern struct list_head ftrace_events;
829 830
830extern const char *__start___trace_bprintk_fmt[]; 831extern const char *__start___trace_bprintk_fmt[];
diff --git a/kernel/trace/trace_event_profile.c b/kernel/trace/trace_event_profile.c
index 7bf2ad65eee5..5b5895afecfe 100644
--- a/kernel/trace/trace_event_profile.c
+++ b/kernel/trace/trace_event_profile.c
@@ -10,21 +10,30 @@
10int ftrace_profile_enable(int event_id) 10int ftrace_profile_enable(int event_id)
11{ 11{
12 struct ftrace_event_call *event; 12 struct ftrace_event_call *event;
13 int ret = -EINVAL;
13 14
15 mutex_lock(&event_mutex);
14 list_for_each_entry(event, &ftrace_events, list) { 16 list_for_each_entry(event, &ftrace_events, list) {
15 if (event->id == event_id) 17 if (event->id == event_id) {
16 return event->profile_enable(event); 18 ret = event->profile_enable(event);
19 break;
20 }
17 } 21 }
22 mutex_unlock(&event_mutex);
18 23
19 return -EINVAL; 24 return ret;
20} 25}
21 26
22void ftrace_profile_disable(int event_id) 27void ftrace_profile_disable(int event_id)
23{ 28{
24 struct ftrace_event_call *event; 29 struct ftrace_event_call *event;
25 30
31 mutex_lock(&event_mutex);
26 list_for_each_entry(event, &ftrace_events, list) { 32 list_for_each_entry(event, &ftrace_events, list) {
27 if (event->id == event_id) 33 if (event->id == event_id) {
28 return event->profile_disable(event); 34 event->profile_disable(event);
35 break;
36 }
29 } 37 }
38 mutex_unlock(&event_mutex);
30} 39}
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index f251a150e75e..8d579ff23610 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -21,7 +21,7 @@
21 21
22#define TRACE_SYSTEM "TRACE_SYSTEM" 22#define TRACE_SYSTEM "TRACE_SYSTEM"
23 23
24static DEFINE_MUTEX(event_mutex); 24DEFINE_MUTEX(event_mutex);
25 25
26LIST_HEAD(ftrace_events); 26LIST_HEAD(ftrace_events);
27 27
@@ -80,6 +80,7 @@ static void ftrace_clear_events(void)
80{ 80{
81 struct ftrace_event_call *call; 81 struct ftrace_event_call *call;
82 82
83 mutex_lock(&event_mutex);
83 list_for_each_entry(call, &ftrace_events, list) { 84 list_for_each_entry(call, &ftrace_events, list) {
84 85
85 if (call->enabled) { 86 if (call->enabled) {
@@ -87,6 +88,7 @@ static void ftrace_clear_events(void)
87 call->unregfunc(); 88 call->unregfunc();
88 } 89 }
89 } 90 }
91 mutex_unlock(&event_mutex);
90} 92}
91 93
92static void ftrace_event_enable_disable(struct ftrace_event_call *call, 94static void ftrace_event_enable_disable(struct ftrace_event_call *call,
@@ -274,6 +276,9 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
274 276
275static void *t_start(struct seq_file *m, loff_t *pos) 277static void *t_start(struct seq_file *m, loff_t *pos)
276{ 278{
279 mutex_lock(&event_mutex);
280 if (*pos == 0)
281 m->private = ftrace_events.next;
277 return t_next(m, NULL, pos); 282 return t_next(m, NULL, pos);
278} 283}
279 284
@@ -303,6 +308,9 @@ s_next(struct seq_file *m, void *v, loff_t *pos)
303 308
304static void *s_start(struct seq_file *m, loff_t *pos) 309static void *s_start(struct seq_file *m, loff_t *pos)
305{ 310{
311 mutex_lock(&event_mutex);
312 if (*pos == 0)
313 m->private = ftrace_events.next;
306 return s_next(m, NULL, pos); 314 return s_next(m, NULL, pos);
307} 315}
308 316
@@ -319,12 +327,12 @@ static int t_show(struct seq_file *m, void *v)
319 327
320static void t_stop(struct seq_file *m, void *p) 328static void t_stop(struct seq_file *m, void *p)
321{ 329{
330 mutex_unlock(&event_mutex);
322} 331}
323 332
324static int 333static int
325ftrace_event_seq_open(struct inode *inode, struct file *file) 334ftrace_event_seq_open(struct inode *inode, struct file *file)
326{ 335{
327 int ret;
328 const struct seq_operations *seq_ops; 336 const struct seq_operations *seq_ops;
329 337
330 if ((file->f_mode & FMODE_WRITE) && 338 if ((file->f_mode & FMODE_WRITE) &&
@@ -332,13 +340,7 @@ ftrace_event_seq_open(struct inode *inode, struct file *file)
332 ftrace_clear_events(); 340 ftrace_clear_events();
333 341
334 seq_ops = inode->i_private; 342 seq_ops = inode->i_private;
335 ret = seq_open(file, seq_ops); 343 return seq_open(file, seq_ops);
336 if (!ret) {
337 struct seq_file *m = file->private_data;
338
339 m->private = ftrace_events.next;
340 }
341 return ret;
342} 344}
343 345
344static ssize_t 346static ssize_t
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index ce07b8186710..7ac691085276 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -408,6 +408,7 @@ static void filter_free_subsystem_preds(struct event_subsystem *system)
408 filter->n_preds = 0; 408 filter->n_preds = 0;
409 } 409 }
410 410
411 mutex_lock(&event_mutex);
411 list_for_each_entry(call, &ftrace_events, list) { 412 list_for_each_entry(call, &ftrace_events, list) {
412 if (!call->define_fields) 413 if (!call->define_fields)
413 continue; 414 continue;
@@ -417,6 +418,7 @@ static void filter_free_subsystem_preds(struct event_subsystem *system)
417 remove_filter_string(call->filter); 418 remove_filter_string(call->filter);
418 } 419 }
419 } 420 }
421 mutex_unlock(&event_mutex);
420} 422}
421 423
422static int filter_add_pred_fn(struct filter_parse_state *ps, 424static int filter_add_pred_fn(struct filter_parse_state *ps,
@@ -567,6 +569,7 @@ static int filter_add_subsystem_pred(struct filter_parse_state *ps,
567{ 569{
568 struct event_filter *filter = system->filter; 570 struct event_filter *filter = system->filter;
569 struct ftrace_event_call *call; 571 struct ftrace_event_call *call;
572 int err = 0;
570 573
571 if (!filter->preds) { 574 if (!filter->preds) {
572 filter->preds = kzalloc(MAX_FILTER_PRED * sizeof(pred), 575 filter->preds = kzalloc(MAX_FILTER_PRED * sizeof(pred),
@@ -584,8 +587,8 @@ static int filter_add_subsystem_pred(struct filter_parse_state *ps,
584 filter->preds[filter->n_preds] = pred; 587 filter->preds[filter->n_preds] = pred;
585 filter->n_preds++; 588 filter->n_preds++;
586 589
590 mutex_lock(&event_mutex);
587 list_for_each_entry(call, &ftrace_events, list) { 591 list_for_each_entry(call, &ftrace_events, list) {
588 int err;
589 592
590 if (!call->define_fields) 593 if (!call->define_fields)
591 continue; 594 continue;
@@ -597,12 +600,13 @@ static int filter_add_subsystem_pred(struct filter_parse_state *ps,
597 if (err) { 600 if (err) {
598 filter_free_subsystem_preds(system); 601 filter_free_subsystem_preds(system);
599 parse_error(ps, FILT_ERR_BAD_SUBSYS_FILTER, 0); 602 parse_error(ps, FILT_ERR_BAD_SUBSYS_FILTER, 0);
600 return err; 603 break;
601 } 604 }
602 replace_filter_string(call->filter, filter_string); 605 replace_filter_string(call->filter, filter_string);
603 } 606 }
607 mutex_unlock(&event_mutex);
604 608
605 return 0; 609 return err;
606} 610}
607 611
608static void parse_init(struct filter_parse_state *ps, 612static void parse_init(struct filter_parse_state *ps,