Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755892AbYLJHM4 (ORCPT ); Wed, 10 Dec 2008 02:12:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754281AbYLJHMr (ORCPT ); Wed, 10 Dec 2008 02:12:47 -0500 Received: from viefep11-int.chello.at ([62.179.121.31]:54718 "EHLO viefep11-int.chello.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753607AbYLJHMr (ORCPT ); Wed, 10 Dec 2008 02:12:47 -0500 X-SourceIP: 213.46.9.244 Subject: Re: [PATCH] percpu_counter: Fix __percpu_counter_sum() From: Peter Zijlstra To: Eric Dumazet Cc: Theodore Tso , Andrew Morton , linux kernel , "David S. Miller" , Mingming Cao , linux-ext4@vger.kernel.org In-Reply-To: <493F4EF4.4080205@cosmosbay.com> References: <4936D287.6090206@cosmosbay.com> <4936EB04.8000609@cosmosbay.com> <20081206202233.3b74febc.akpm@linux-foundation.org> <493BCF60.1080409@cosmosbay.com> <20081207092854.f6bcbfae.akpm@linux-foundation.org> <493C0F40.7040304@cosmosbay.com> <20081207205250.dbb7fe4b.akpm@linux-foundation.org> <20081208221241.GA2501@mit.edu> <1228774836.16244.22.camel@lappy.programming.kicks-ass.net> <20081208230047.GC2501@mit.edu> <1228777500.12729.4.camel@twins> <493E2884.6010600@cosmosbay.com> <1228811653.6809.26.camel@twins> <493F4EF4.4080205@cosmosbay.com> Content-Type: text/plain Date: Wed, 10 Dec 2008 08:12:42 +0100 Message-Id: <1228893162.6978.25.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.24.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1380 Lines: 42 On Wed, 2008-12-10 at 06:09 +0100, Eric Dumazet wrote: > Now percpu_counter_sum() is 'fixed', what about "percpu_counter_add()" ? > > void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch) > { > s64 count; > s32 *pcount; > int cpu = get_cpu(); > > pcount = per_cpu_ptr(fbc->counters, cpu); > count = *pcount + amount; > if (count >= batch || count <= -batch) { > spin_lock(&fbc->lock); > fbc->count += count; > *pcount = 0; > spin_unlock(&fbc->lock); > } else { > *pcount = count; > } > put_cpu(); > } > > > If I read this well, this is not IRQ safe. > > get_cpu() only disables preemption IMHO > > For nr_files, nr_dentry, nr_inodes, it should not be a problem. > > But for network counters (only in net-next-2.6) > and lib/proportions.c, we have a problem ? Non of percpu_counter if irqsafe, for lib/proportions I disabled irqs by hand when needed - I don't think we ought to bother with local_t, esp as it basically sucks chunks on anything !x86. -- 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/