From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758649Ab2DXXyW (ORCPT ); Tue, 24 Apr 2012 19:54:22 -0400 Received: from mailout4.samsung.com ([203.254.224.34]:33348 "EHLO mailout4.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753468Ab2DXXyV (ORCPT ); Tue, 24 Apr 2012 19:54:21 -0400 X-AuditID: cbfee61a-b7b8eae00000534b-ae-4f973d2b61c5 Message-id: <4F973D2B.7000205@samsung.com> Date: Wed, 25 Apr 2012 08:54:19 +0900 From: Minho Ban User-Agent: Mozilla/5.0 (X11; Linux i686; rv:11.0) Gecko/20120329 Thunderbird/11.0.1 MIME-version: 1.0 To: Steven Rostedt Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Frederic Weisbecker , Peter Zijlstra , Paul Turner , Thomas Gleixner , Hidetoshi Seto , "Paul E. McKenney" , Josh Triplett Subject: Re: [RFC/PATCH] Prevent wasting time to find out get_parent_ip References: <4F969E53.9080307@samsung.com> <1335291397.28106.142.camel@gandalf.stny.rr.com> In-reply-to: <1335291397.28106.142.camel@gandalf.stny.rr.com> Content-type: text/plain; charset=ISO-8859-15 Content-transfer-encoding: 7bit X-Brightmail-Tracker: AAAAAA== X-TM-AS-MML: No Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/25/2012 03:16 AM, Steven Rostedt wrote: > On Tue, 2012-04-24 at 21:36 +0900, Minho Ban wrote: >> trace_preempt_on/off looks empty if PREEMPT_TRACER is off. But actually it is >> spending time to find out get_parent_ip(even CALLER_ADDR for some ARCH) which is >> in argument. This seems not fair for those who expect to do nothing but increase >> or decrease count. >> > > Yuck what an ugly patch. Please don't uglify the C code with #ifdefs! > Yes, I agree. >> Cc: Thomas Gleixner >> Signed-off-by: Minho Ban >> --- >> include/linux/ftrace.h | 3 --- >> kernel/sched/core.c | 5 ++++- >> kernel/softirq.c | 3 ++- >> 3 files changed, 6 insertions(+), 5 deletions(-) >> >> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h >> index 72a6cab..7cd11fe 100644 >> --- a/include/linux/ftrace.h >> +++ b/include/linux/ftrace.h >> @@ -484,9 +484,6 @@ static inline void __ftrace_enabled_restore(int enabled) >> #ifdef CONFIG_PREEMPT_TRACER >> 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) { } > > If you want to hide the "CALLER_ADDR" for other archs, then simply do: > > # define trace_preempt_on(a0, a1) do { } while (0) > # define trace_preempt_off(a0, a1) do { } while (0) > > and be done with it. > > Oh, you should add a comment before these defines to the effect of: > > /* > * 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. > */ > > That way, you will document why we use defines instead of static > inlines. > > -- Steve > Very appreciate your explanation and detailed(even complete) sample code. I'll apply your code. >> #endif >> >> #ifdef CONFIG_FTRACE_MCOUNT_RECORD >> diff --git a/kernel/sched/core.c b/kernel/sched/core.c >> index 4603b9d..efdd5a0 100644 >> --- a/kernel/sched/core.c >> +++ b/kernel/sched/core.c >> @@ -3068,8 +3068,10 @@ void __kprobes add_preempt_count(int val) >> DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >= >> PREEMPT_MASK - 10); >> #endif >> +#ifdef CONFIG_PREEMPT_TRACER >> if (preempt_count() == val) >> trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1)); >> +#endif >> } >> EXPORT_SYMBOL(add_preempt_count); >> >> @@ -3088,9 +3090,10 @@ void __kprobes sub_preempt_count(int val) >> !(preempt_count() & PREEMPT_MASK))) >> return; >> #endif >> - >> +#ifdef CONFIG_PREEMPT_TRACER >> if (preempt_count() == val) >> trace_preempt_on(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1)); >> +#endif >> preempt_count() -= val; >> } >> EXPORT_SYMBOL(sub_preempt_count); >> diff --git a/kernel/softirq.c b/kernel/softirq.c >> index 671f959..e7c8336 100644 >> --- a/kernel/softirq.c >> +++ b/kernel/softirq.c >> @@ -112,9 +112,10 @@ static void __local_bh_disable(unsigned long ip, unsigned int cnt) >> if (softirq_count() == cnt) >> trace_softirqs_off(ip); >> raw_local_irq_restore(flags); >> - >> +#ifdef CONFIG_PREEMPT_TRACER >> if (preempt_count() == cnt) >> trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1)); >> +#endif >> } >> #else /* !CONFIG_TRACE_IRQFLAGS */ >> static inline void __local_bh_disable(unsigned long ip, unsigned int cnt) > > >