From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754219Ab3KELVh (ORCPT ); Tue, 5 Nov 2013 06:21:37 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:53699 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753475Ab3KELVf (ORCPT ); Tue, 5 Nov 2013 06:21:35 -0500 Date: Tue, 5 Nov 2013 03:21:30 -0800 From: "Paul E. McKenney" To: Steven Rostedt Cc: LKML Subject: Re: [PATCH] rcu: Do not trace rcu_is_watching() functions Message-ID: <20131105112130.GC3947@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20131104202736.72dd8e45@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131104202736.72dd8e45@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13110511-6688-0000-0000-0000032F0AAC Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 04, 2013 at 08:27:36PM -0500, Steven Rostedt wrote: > > Paul, > > As I added the rcu_is_watching() to the ftrace code to prevent perf > from tracing functions where RCU is not watching, I noticed that the > rcu_is_watching() functions can themselves be traced. I would say this > is a helper function and not something that we need to trace, as it can > cause a slowdown in function tracing (any recursion is detected, so it > only affects performance). > > I marked the functions with notrace. You can take this patch and push > it for 3.13 or I can take it if you give me an "Acked-by". As it only > affects performance and does not crash the code it's not a must have in > my tree. > > If you take it, I can write up a better change log too. > > -- Steve > > Signed-off-by: Steven Rostedt Given an improved commit log: Acked-by: Paul E. McKenney > diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c > index 0fa061d..590c8a8 100644 > --- a/kernel/rcutiny.c > +++ b/kernel/rcutiny.c > @@ -179,7 +179,7 @@ EXPORT_SYMBOL_GPL(rcu_irq_enter); > /* > * Test whether RCU thinks that the current CPU is idle. > */ > -bool __rcu_is_watching(void) > +bool notrace __rcu_is_watching(void) > { > return rcu_dynticks_nesting; > } > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index 981d0c1..499bb2b 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -662,7 +662,7 @@ void rcu_nmi_exit(void) > * rcu_is_watching(), the caller of __rcu_is_watching() must have at > * least disabled preemption. > */ > -bool __rcu_is_watching(void) > +bool notrace __rcu_is_watching(void) > { > return atomic_read(this_cpu_ptr(&rcu_dynticks.dynticks)) & 0x1; > } > @@ -673,7 +673,7 @@ bool __rcu_is_watching(void) > * If the current CPU is in its idle loop and is neither in an interrupt > * or NMI handler, return true. > */ > -bool rcu_is_watching(void) > +bool notrace rcu_is_watching(void) > { > int ret; > >