From: Steven Rostedt <rostedt@goodmis.org>
Date: Tue, 15 Jul 2008 13:53:37 +0000 (-0400)
Subject: ftrace: only trace preempt off with preempt tracer
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=1e01cb0c6ff7e9ddb6547551794c6aa82785a7cb;p=deliverable%2Flinux.git

ftrace: only trace preempt off with preempt tracer

When PREEMPT_TRACER and IRQSOFF_TRACER are both configured and irqsoff
tracer is running, the preempt_off sections might also be traced.

Thanks to Andrew Morton for pointing out my mistake of spin_lock disabling
interrupts while he was reviewing ftrace.txt. Seems that my example I used
actually hit this bug.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 421d6fe3650e..b1e4a89b08eb 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -337,12 +337,14 @@ EXPORT_SYMBOL(trace_hardirqs_off_caller);
 #ifdef CONFIG_PREEMPT_TRACER
 void trace_preempt_on(unsigned long a0, unsigned long a1)
 {
-	stop_critical_timing(a0, a1);
+	if (preempt_trace())
+		stop_critical_timing(a0, a1);
 }
 
 void trace_preempt_off(unsigned long a0, unsigned long a1)
 {
-	start_critical_timing(a0, a1);
+	if (preempt_trace())
+		start_critical_timing(a0, a1);
 }
 #endif /* CONFIG_PREEMPT_TRACER */