Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752588AbaLNDOp (ORCPT ); Sat, 13 Dec 2014 22:14:45 -0500 Received: from zeniv.linux.org.uk ([195.92.253.2]:59566 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751361AbaLNDOo (ORCPT ); Sat, 13 Dec 2014 22:14:44 -0500 Date: Sun, 14 Dec 2014 03:14:29 +0000 From: Al Viro To: Linus Torvalds Cc: Dave Jones , Chris Mason , Mike Galbraith , Ingo Molnar , Peter Zijlstra , =?iso-8859-1?Q?D=E2niel?= Fraga , Sasha Levin , "Paul E. McKenney" , Linux Kernel Mailing List , Thomas Gleixner Subject: Re: frequent lockups in 3.18rc4 Message-ID: <20141214031429.GR22149@ZenIV.linux.org.uk> References: <20141213223616.GA22559@redhat.com> <20141213233508.GN22149@ZenIV.linux.org.uk> <20141213234730.GP22149@ZenIV.linux.org.uk> <20141214003332.GQ22149@ZenIV.linux.org.uk> 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) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Dec 13, 2014 at 05:35:17PM -0800, Linus Torvalds wrote: > 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. Right you are - I really need to get some coffee... Sorry... FWIW, do we need to disable interrupts there? After all, mnt_want_write() and mnt_drop_write() shouldn't be done from interrupt context - they can happen via schedule_delayed_work(), but that's it... -- 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/