Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753369Ab1DRHnw (ORCPT ); Mon, 18 Apr 2011 03:43:52 -0400 Received: from mga02.intel.com ([134.134.136.20]:29987 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751246Ab1DRHns (ORCPT ); Mon, 18 Apr 2011 03:43:48 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.64,231,1301900400"; d="scan'208";a="734920275" Subject: Re: [patch v3 3/3] percpu_counter: use atomic64 for counter in SMP From: Shaohua Li To: Tejun Heo Cc: "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "cl@linux.com" , "eric.dumazet@gmail.com" In-Reply-To: <20110415041506.GC29512@mtj.dyndns.org> References: <20110414020447.979946152@sli10-conroe.sh.intel.com> <20110414020747.411215973@sli10-conroe.sh.intel.com> <20110415041506.GC29512@mtj.dyndns.org> Content-Type: text/plain; charset="UTF-8" Date: Mon, 18 Apr 2011 15:43:45 +0800 Message-ID: <1303112625.3981.191.camel@sli10-conroe> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1452 Lines: 40 On Fri, 2011-04-15 at 12:15 +0800, Tejun Heo wrote: > Hello, > > On Thu, Apr 14, 2011 at 10:04:50AM +0800, shaohua.li@intel.com wrote: > > Index: linux/lib/percpu_counter.c > > =================================================================== > > --- linux.orig/lib/percpu_counter.c 2011-04-14 09:53:04.000000000 +0800 > > +++ linux/lib/percpu_counter.c 2011-04-14 10:01:29.000000000 +0800 > > @@ -59,13 +59,17 @@ void percpu_counter_set(struct percpu_co > > { > > int cpu; > > > > - spin_lock(&fbc->lock); > > + /* > > + * Don't really need to disable preempt here, just make sure there is > > + * no big latency because of preemption > > + */ > > + preempt_disable(); > > for_each_possible_cpu(cpu) { > > s32 *pcount = per_cpu_ptr(fbc->counters, cpu); > > *pcount = 0; > > } > > - fbc->count = amount; > > - spin_unlock(&fbc->lock); > > + atomic64_set(&fbc->count, amount); > > + preempt_enable(); > > Disabling preemption here doesn't make any sense. > percpu_counter_set() inherently requires its users to guarantee that > no other user is modifying the percpu counter. ha, ok. should I still rebase the patch against Christoph's patch? Looks that one is still not settled down. -- 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/