From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxim Levitsky Subject: QUESTION: How to fix race between .suspend routine and watchdog timer Date: Thu, 25 Oct 2007 06:12:44 +0200 Message-ID: <200710250612.44296.maximlevitsky@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: linux-pm@lists.linux-foundation.org, netdev@vger.kernel.org To: linux-kernel@vger.kernel.org Return-path: Received: from ug-out-1314.google.com ([66.249.92.174]:9798 "EHLO ug-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753100AbXJYENb (ORCPT ); Thu, 25 Oct 2007 00:13:31 -0400 Received: by ug-out-1314.google.com with SMTP id z38so440619ugc for ; Wed, 24 Oct 2007 21:13:29 -0700 (PDT) Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Hi, Recently, trying to fix saa7134 suspend/resume problems I found that there is a race between IRQ handler and .suspend , and that I cant let driver access the device while its in D3 since it can lock up some systems. Now I am looking to fix those issues in two drivers that have my .suspend/.resume routines. the saa7134 capture chip and dmfe, the davicom network driver. 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. I can put checks in the timer for ->insuspend, and don't re enable it if set, but that opens a new can of worms with memory barriers, etc... So please tell me how properly to do that. By the way, this problem, together with synchronize_irq it very generic, since most drivers have and irq handler, and a timeout timer. Best regards, Maxim Levitsky