Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756375AbXJ0TSN (ORCPT ); Sat, 27 Oct 2007 15:18:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752465AbXJ0TR4 (ORCPT ); Sat, 27 Oct 2007 15:17:56 -0400 Received: from netrider.rowland.org ([192.131.102.5]:3112 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751954AbXJ0TR4 (ORCPT ); Sat, 27 Oct 2007 15:17:56 -0400 Date: Sat, 27 Oct 2007 15:17:55 -0400 (EDT) From: Alan Stern X-X-Sender: stern@netrider.rowland.org To: Maxim Levitsky cc: linux-kernel@vger.kernel.org, , Subject: Re: [linux-pm] QUESTION: How to fix race between .suspend routine and watchdog timer In-Reply-To: <200710261348.42748.maximlevitsky@gmail.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1510 Lines: 31 On Fri, 26 Oct 2007, Maxim Levitsky wrote: > > > Looking through the dmfe code, I noticed yet another possible race. > > > A race between the .suspend, and a timer that serves both as a watchdog, and link state detector. > > > Again I need to prevent it from running during the suspend/resume, but how? > > > > > > I can use del_timer in .suspend, and mod_timer in .resume, but that doesn't protect against > > > race with already running timer. > > > I can use del_timer_sync, but it states that it is useless if timer re-enables itself, and I agree with that. > > > In dmfe case the timer does re-enable itself. > > > > That comment isn't right. del_timer_sync works perfectly well even if > > the timer routine re-enables itself, provided it stops doing so after a > > small number of iterations. > Thanks for the info. but.... > Due to the "don't access the hardware, while powered-off" rule, I must know that the timer isn't running. > and won't be. > So what function to use (if possible) to be sure that the timer won't run anymore? > (Taking in the account the fact that it re-enables itself) Use del_timer_sync(). It guarantees that when it returns, the timer will be stopped and the timer routine will no longer be running on any CPU. Alan Stern - 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/