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authorLi Zefan <lizf@cn.fujitsu.com>2009-06-24 09:52:29 +0800
committerIngo Molnar <mingo@elte.hu>2009-06-24 11:02:49 +0200
commite1c7e2a6e67fe9db19dd15e71614526a31b5fdb1 (patch)
tree0b6eb8cf5e699592fc868a44b24e603ad8f3d6af /kernel/trace
parent4e8a2372f9255a1464ef488ed925455f53fbdaa1 (diff)
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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/trace')
-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)
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)