From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: question on resume() Date: Wed, 31 Jan 2007 09:33:28 +0100 Message-ID: <200701310933.29443.rjw@sisk.pl> References: <200701291206.39637.oneukum@suse.de> <200701301750.48196.oliver@neukum.name> <200701302332.26063.rjw@sisk.pl> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <200701302332.26063.rjw@sisk.pl> 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 On Tuesday, 30 January 2007 23:32, Rafael J. Wysocki wrote: > [Added linux-pm to the Cc list, because I'm going to talk about things th= at > 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 qu= estion > > > 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). Ah, sorry, I've just realized I was wrong. Processes in TASK_UNINTERRUPTIB= LE cannot be frozen! So, the above only applies to wake_up_interruptible(). You don't need to call wake_up() from .resume(), because there are no tasks to be notified this way and you shouldn't call wake_up_interruptible() from there. Greetings, Rafael -- = If you don't have the time to read, you don't have the time or the tools to write. - Stephen King