Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756431AbaDPSsD (ORCPT ); Wed, 16 Apr 2014 14:48:03 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:33542 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755352AbaDPSr7 (ORCPT ); Wed, 16 Apr 2014 14:47:59 -0400 Date: Wed, 16 Apr 2014 11:47:55 -0700 From: "Paul E. McKenney" To: Christoph Lameter Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, tj@kernel.org, grygorii.strashko@ti.com, peterz@infradead.org Subject: Re: How do I increment a per-CPU variable without warning? Message-ID: <20140416184755.GY4496@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20140415221755.GA27188@linux.vnet.ibm.com> <20140416160621.GX4496@linux.vnet.ibm.com> <20140416171230.GA8788@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14041618-1542-0000-0000-00000122EAFB Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 16, 2014 at 01:29:21PM -0500, Christoph Lameter wrote: > On Wed, 16 Apr 2014, Paul E. McKenney wrote: > > > On Wed, Apr 16, 2014 at 09:06:21AM -0700, Paul E. McKenney wrote: > > > On Wed, Apr 16, 2014 at 10:08:03AM -0500, Christoph Lameter wrote: > > > > On Tue, 15 Apr 2014, Paul E. McKenney wrote: > > > > > > > > > Hello, Christoph, > > > > > > > > > > I have a patch that currently uses __this_cpu_inc_return() to increment a > > > > > per-CPU variable, but without preemption disabled. Of course, given that > > > > > preemption is enabled, it might well end up picking up one CPU's counter, > > > > > adding one to it, then storing the result into some other CPU's counter. > > > > > But this is OK, the test can be probabilistic. And when I run this > > > > > against v3.14 and earlier, it works fine. > > > > > > > > We introduced raw_cpu_inc_return to squish these warnings. > > > > > > Cool, this is a good short-term fix. > > > > Or at least it is given the following patch. Was this the intent? > > Correct. Thanks for the fix. > > Acked-by: Christoph Lameter Queued, thank you. I don't need this until 3.16, but I am tempted to push it in this cycle in case others need it. Any objections? Thanx, Paul > > ------------------------------------------------------------------------ > > > > percpu: Fix raw_cpu_inc_return() > > > > The definition for raw_cpu_add_return() uses the operation prefix > > "raw_add_return_", but the definitions in the various percpu.h files > > expect "raw_cpu_add_return_". This commit therefore appropriately > > adjusts the definition of raw_cpu_add_return(). > > > > Signed-off-by: Paul E. McKenney > > Cc: Christoph Lameter > > > > diff --git a/include/linux/percpu.h b/include/linux/percpu.h > > index e7a0b95ed527..495c6543a8f2 100644 > > --- a/include/linux/percpu.h > > +++ b/include/linux/percpu.h > > @@ -639,7 +639,7 @@ do { \ > > # define raw_cpu_add_return_8(pcp, val) raw_cpu_generic_add_return(pcp, val) > > # endif > > # define raw_cpu_add_return(pcp, val) \ > > - __pcpu_size_call_return2(raw_add_return_, pcp, val) > > + __pcpu_size_call_return2(raw_cpu_add_return_, pcp, val) > > #endif > > > > #define raw_cpu_sub_return(pcp, val) raw_cpu_add_return(pcp, -(typeof(pcp))(val)) > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/