[PATCH 2/2] ring-buffer: no preempt for sched_clock

[Steven Rostedt <rostedt@goodmis.org>]

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Impact: disable preemption no calling sched_clock

The ring_buffer_time_stamp still uses sched_clock as its counter.
But it is a bug to call it with preemption enabled. This requirement
should not be pushed to the ring_buffer_time_stamp callers, so
the ring_buffer_time_stamp needs to disable preemption when calling
sched_clock.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
 kernel/trace/ring_buffer.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 86dc353..2d6c2cf 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -53,8 +53,14 @@ void tracing_off(void)
 /* FIXME!!! */
 u64 ring_buffer_time_stamp(int cpu)
 {
+	u64 time;
+
+	preempt_disable_notrace();
 	/* shift to debug/test normalization and TIME_EXTENTS */
-	return sched_clock() << DEBUG_SHIFT;
+	time = sched_clock() << DEBUG_SHIFT;
+	preempt_enable_notrace();
+
+	return time;
 }
 
 void ring_buffer_normalize_time_stamp(int cpu, u64 *ts)
-- 
1.5.6.5

--