tracing/ftrace: use preempt_enable_no_resched_notrace in ring_buffer_time_stamp()

Impact: prevent a trace recursion

After some tests with function graph tracer under x86-32, I saw some recursions
caused by ring_buffer_time_stamp() that calls preempt_enable_no_notrace() which
calls preempt_schedule() which is traced itself.

This patch re-enables preemption without rescheduling.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 7f69cfeaadf76a1bc002df343d2006ed20204a5e..eab81f918f6a0afe40cf5bcfb6f1e869213c26a4 100644 (file)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -107,7 +107,7 @@ u64 ring_buffer_time_stamp(int cpu)
        preempt_disable_notrace();
        /* shift to debug/test normalization and TIME_EXTENTS */
        time = sched_clock() << DEBUG_SHIFT;
-       preempt_enable_notrace();
+       preempt_enable_no_resched_notrace();
 
        return time;
 }