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| author | Li Zefan <lizf@cn.fujitsu.com> | 2009-06-24 09:52:29 +0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-06-24 11:02:49 +0200 |
| commit | e1c7e2a6e67fe9db19dd15e71614526a31b5fdb1 (patch) | |
| tree | 0b6eb8cf5e699592fc868a44b24e603ad8f3d6af | |
| parent | 4e8a2372f9255a1464ef488ed925455f53fbdaa1 (diff) | |
| download | linux-e1c7e2a6e67fe9db19dd15e71614526a31b5fdb1.tar.gz linux-e1c7e2a6e67fe9db19dd15e71614526a31b5fdb1.tar.bz2 linux-e1c7e2a6e67fe9db19dd15e71614526a31b5fdb1.zip | |
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>
| -rw-r--r-- | kernel/trace/trace_events.c | 28 |
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) static void *t_start(struct seq_file *m, loff_t *pos) { + struct ftrace_event_call *call = NULL; + loff_t l; + mutex_lock(&event_mutex); - if (*pos == 0) - m->private = ftrace_events.next; - return t_next(m, NULL, pos); + + m->private = ftrace_events.next; + for (l = 0; l <= *pos; ) { + call = t_next(m, NULL, &l); + if (!call) + break; + } + return call; } static void * @@ -332,10 +340,18 @@ s_next(struct seq_file *m, void *v, loff_t *pos) static void *s_start(struct seq_file *m, loff_t *pos) { + struct ftrace_event_call *call = NULL; + loff_t l; + mutex_lock(&event_mutex); - if (*pos == 0) - m->private = ftrace_events.next; - return s_next(m, NULL, pos); + + m->private = ftrace_events.next; + for (l = 0; l <= *pos; ) { + call = s_next(m, NULL, &l); + if (!call) + break; + } + return call; } static int t_show(struct seq_file *m, void *v) |