tracing/events: don't use wake up for events
Impact: fix hard-lockup with sched switch events
Some ftrace events, such as sched wakeup, can be traced
while the runqueue lock is hold. Since they are using
trace_current_buffer_unlock_commit(), they call wake_up()
which can try to grab the runqueue lock too, resulting in
a deadlock.
Now for all event, we call a new helper:
trace_nowake_buffer_unlock_commit() which do pretty the same than
trace_current_buffer_unlock_commit() except than it doesn't call
trace_wake_up().
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1237759847-21025-4-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e6fac0f..6bad128 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -860,15 +860,25 @@
static void ftrace_trace_userstack(struct trace_array *tr,
unsigned long flags, int pc);
-void trace_buffer_unlock_commit(struct trace_array *tr,
- struct ring_buffer_event *event,
- unsigned long flags, int pc)
+static inline void __trace_buffer_unlock_commit(struct trace_array *tr,
+ struct ring_buffer_event *event,
+ unsigned long flags, int pc,
+ int wake)
{
ring_buffer_unlock_commit(tr->buffer, event);
ftrace_trace_stack(tr, flags, 6, pc);
ftrace_trace_userstack(tr, flags, pc);
- trace_wake_up();
+
+ if (wake)
+ trace_wake_up();
+}
+
+void trace_buffer_unlock_commit(struct trace_array *tr,
+ struct ring_buffer_event *event,
+ unsigned long flags, int pc)
+{
+ __trace_buffer_unlock_commit(tr, event, flags, pc, 1);
}
struct ring_buffer_event *
@@ -882,7 +892,13 @@
void trace_current_buffer_unlock_commit(struct ring_buffer_event *event,
unsigned long flags, int pc)
{
- return trace_buffer_unlock_commit(&global_trace, event, flags, pc);
+ return __trace_buffer_unlock_commit(&global_trace, event, flags, pc, 1);
+}
+
+void trace_nowake_buffer_unlock_commit(struct ring_buffer_event *event,
+ unsigned long flags, int pc)
+{
+ return __trace_buffer_unlock_commit(&global_trace, event, flags, pc, 0);
}
void