Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752239AbaLNBfU (ORCPT ); Sat, 13 Dec 2014 20:35:20 -0500 Received: from mail-qg0-f48.google.com ([209.85.192.48]:54882 "EHLO mail-qg0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751381AbaLNBfT (ORCPT ); Sat, 13 Dec 2014 20:35:19 -0500 MIME-Version: 1.0 In-Reply-To: <20141214003332.GQ22149@ZenIV.linux.org.uk> References: <20141213165915.GA12756@redhat.com> <20141213223616.GA22559@redhat.com> <20141213233508.GN22149@ZenIV.linux.org.uk> <20141213234730.GP22149@ZenIV.linux.org.uk> <20141214003332.GQ22149@ZenIV.linux.org.uk> Date: Sat, 13 Dec 2014 17:35:17 -0800 X-Google-Sender-Auth: ddRv0H_HfgRyRUlXeUSKHu1wW3c Message-ID: Subject: Re: frequent lockups in 3.18rc4 From: Linus Torvalds To: Al Viro Cc: Dave Jones , Chris Mason , Mike Galbraith , Ingo Molnar , Peter Zijlstra , =?UTF-8?Q?D=C3=A2niel_Fraga?= , Sasha Levin , "Paul E. McKenney" , Linux Kernel Mailing List , Thomas Gleixner Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Dec 13, 2014 at 4:33 PM, Al Viro wrote: > > So does SMP - this_cpu_dec() relies on preemption being disabled. No. really. It very much does not. Not on x86, not elsewhere. It's part of the whole point of "this_cpu_p()". They are preemption and interrupt safe. It's the "__this_cpu_op()" ones that need external protection. Linus -- 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/