linux-kernel - [PATCH] tracing: Prevent wasting time evaluating parameters in trace_preempt

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Message-id: <4FA73510.7070705@samsung.com>
Date:	Mon, 07 May 2012 11:36:00 +0900
From:	Minho Ban <mhban@...sung.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Turner <pjt@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Josh Triplett <josh@...htriplett.org>
Subject: [PATCH] tracing: Prevent wasting time evaluating parameters in
 trace_preempt_on/off

This fixes spending time for evaluating parameters in trace_preempt_on/off when
the tracer config is off.

The patch mainly inspired by Steven Rostedt, thanks Steven.

Cc: Ingo Molnar <mingo@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Paul Turner <pjt@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Josh Triplett <josh@...htriplett.org>
Signed-off-by: Minho Ban <mhban@...sung.com>
Acked-by: Steven Rostedt <rostedt@...dmis.org>
---
 include/linux/ftrace.h |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 72a6cab..bc7af66 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -485,8 +485,12 @@ static inline void __ftrace_enabled_restore(int enabled)
   extern void trace_preempt_on(unsigned long a0, unsigned long a1);
   extern void trace_preempt_off(unsigned long a0, unsigned long a1);
 #else
-  static inline void trace_preempt_on(unsigned long a0, unsigned long a1) { }
-  static inline void trace_preempt_off(unsigned long a0, unsigned long a1) { }
+/*
+ * Use defines instead of static inlines because some arches will make code out
+ * of the CALLER_ADDR, when we really want these to be a real nop.
+ */
+# define trace_preempt_on(a0, a1) do { } while (0)
+# define trace_preempt_off(a0, a1) do { } while (0)
 #endif
 
 #ifdef CONFIG_FTRACE_MCOUNT_RECORD
-- 
1.7.5.4

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