aboutsummaryrefslogtreecommitdiffstats
path: root/kernel
diff options
context:
space:
mode:
authorLi Zefan <lizf@cn.fujitsu.com>2009-06-23 21:52:29 -0400
committerIngo Molnar <mingo@elte.hu>2009-06-24 05:02:49 -0400
commite1c7e2a6e67fe9db19dd15e71614526a31b5fdb1 (patch)
tree0b6eb8cf5e699592fc868a44b24e603ad8f3d6af /kernel
parent4e8a2372f9255a1464ef488ed925455f53fbdaa1 (diff)
tracing/events: Don't increment @pos in s_start()
While testing syscall tracepoints posted by Jason, I found 3 entries were missing when reading available_events. The output size of available_events is < 4 pages, which means we lost 1 entry per page. The cause is, it's wrong to increment @pos in s_start(). Actually there's another bug here -- reading avaiable_events/set_events can race with module unload: # cat available_events | s_start() | s_stop() | | # rmmod foo.ko s_start() | call = list_entry(m->private) | @call might be freed and accessing it will lead to crash. Reviewed-by: Liming Wang <liming.wang@windriver.com> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <4A4186DD.6090405@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace_events.c28
1 files changed, 22 insertions, 6 deletions
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index aa08be69a1b6..53c8fd376a88 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -300,10 +300,18 @@ t_next(struct seq_file *m, void *v, loff_t *pos)
300 300
301static void *t_start(struct seq_file *m, loff_t *pos) 301static void *t_start(struct seq_file *m, loff_t *pos)
302{ 302{
303 struct ftrace_event_call *call = NULL;
304 loff_t l;
305
303 mutex_lock(&event_mutex); 306 mutex_lock(&event_mutex);
304 if (*pos == 0) 307
305 m->private = ftrace_events.next; 308 m->private = ftrace_events.next;
306 return t_next(m, NULL, pos); 309 for (l = 0; l <= *pos; ) {
310 call = t_next(m, NULL, &l);
311 if (!call)
312 break;
313 }
314 return call;
307} 315}
308 316
309static void * 317static void *
@@ -332,10 +340,18 @@ s_next(struct seq_file *m, void *v, loff_t *pos)
332 340
333static void *s_start(struct seq_file *m, loff_t *pos) 341static void *s_start(struct seq_file *m, loff_t *pos)
334{ 342{
343 struct ftrace_event_call *call = NULL;
344 loff_t l;
345
335 mutex_lock(&event_mutex); 346 mutex_lock(&event_mutex);
336 if (*pos == 0) 347
337 m->private = ftrace_events.next; 348 m->private = ftrace_events.next;
338 return s_next(m, NULL, pos); 349 for (l = 0; l <= *pos; ) {
350 call = s_next(m, NULL, &l);
351 if (!call)
352 break;
353 }
354 return call;
339} 355}
340 356
341static int t_show(struct seq_file *m, void *v) 357static int t_show(struct seq_file *m, void *v)