From: Frederic Weisbecker <fweisbec@gmail.com>
Date: Tue, 16 Dec 2008 21:08:58 +0000 (+0100)
Subject: tracing/ftrace: use preempt_enable_no_resched_notrace in ring_buffer_time_stamp()
X-Git-Tag: v2.6.29-rc1~586^2~11
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=2c2d7329d8afa9efa3ec24e19a53e7be9d14f242;p=linux-2.6-omap-h63xx.git

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 7f69cfeaadf..eab81f918f6 100644
--- 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;
 }