From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: question on resume() Date: Tue, 30 Jan 2007 23:32:25 +0100 Message-ID: <200701302332.26063.rjw@sisk.pl> References: <200701291206.39637.oneukum@suse.de> <200701301732.56444.rjw@sisk.pl> <200701301750.48196.oliver@neukum.name> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <200701301750.48196.oliver@neukum.name> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.osdl.org Errors-To: linux-pm-bounces@lists.osdl.org To: Oliver Neukum Cc: pm list , linux-kernel@vger.kernel.org List-Id: linux-pm@vger.kernel.org [Added linux-pm to the Cc list, because I'm going to talk about things that I know only from reading the code.] On Tuesday, 30 January 2007 17:50, Oliver Neukum wrote: > Am Dienstag, 30. Januar 2007 17:32 schrieb Rafael J. Wysocki: > > However, you can always inspect the PF_FROZEN flag of the tasks in ques= tion > > if that's practicable. > = > What would I do with that information? Ignore completion of IO? I probably should say "that depends", but that wouldn't be very helpful. Getting back to your initial question, which is if wake_up() may be called from a driver's .resume() routine, I think the answer is no, it may not, because in that case the "notified" tasks would be removed from the wait queue, but the refrigerator() would (wrongly) restore their states as TASK_UNINTERRUPTIBLE (or TASK_INTERRUPTIBLE for wake_up_interruptible()). Generally, you are safe if your driver only calls wake_up() from a process context, but not from .resume() or .suspend() routines (or from an unfreezeable kernel thread). Greetings, Rafael -- = If you don't have the time to read, you don't have the time or the tools to write. - Stephen King From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751851AbXA3Wbp (ORCPT ); Tue, 30 Jan 2007 17:31:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751866AbXA3Wbp (ORCPT ); Tue, 30 Jan 2007 17:31:45 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:40765 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751851AbXA3Wbn (ORCPT ); Tue, 30 Jan 2007 17:31:43 -0500 From: "Rafael J. Wysocki" To: Oliver Neukum Subject: Re: question on resume() Date: Tue, 30 Jan 2007 23:32:25 +0100 User-Agent: KMail/1.9.1 Cc: linux-kernel@vger.kernel.org, nigel@nigel.suspend2.net, pm list References: <200701291206.39637.oneukum@suse.de> <200701301732.56444.rjw@sisk.pl> <200701301750.48196.oliver@neukum.name> In-Reply-To: <200701301750.48196.oliver@neukum.name> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200701302332.26063.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org [Added linux-pm to the Cc list, because I'm going to talk about things that I know only from reading the code.] On Tuesday, 30 January 2007 17:50, Oliver Neukum wrote: > Am Dienstag, 30. Januar 2007 17:32 schrieb Rafael J. Wysocki: > > However, you can always inspect the PF_FROZEN flag of the tasks in question > > if that's practicable. > > What would I do with that information? Ignore completion of IO? I probably should say "that depends", but that wouldn't be very helpful. Getting back to your initial question, which is if wake_up() may be called from a driver's .resume() routine, I think the answer is no, it may not, because in that case the "notified" tasks would be removed from the wait queue, but the refrigerator() would (wrongly) restore their states as TASK_UNINTERRUPTIBLE (or TASK_INTERRUPTIBLE for wake_up_interruptible()). Generally, you are safe if your driver only calls wake_up() from a process context, but not from .resume() or .suspend() routines (or from an unfreezeable kernel thread). Greetings, Rafael -- If you don't have the time to read, you don't have the time or the tools to write. - Stephen King