From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Neukum Subject: Re: question on resume() Date: Wed, 31 Jan 2007 17:12:51 +0100 (MET) Message-ID: <200701311713.04104.oliver@neukum.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: 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: Alan Stern Cc: pm list , linux-kernel@vger.kernel.org, Pavel Machek List-Id: linux-pm@vger.kernel.org Am Mittwoch, 31. Januar 2007 16:54 schrieb Alan Stern: > On Wed, 31 Jan 2007, Pavel Machek wrote: > > "cease IO"? No, I believe it is enough not to start new I/O. Userspace > > is frozen at that point, it can't ask you to do I/O. > = > There may be I/O requests sitting in a queue, already submitted by > userspace. The suspend method should wait for existing I/O to complete > and stop processing new entries from the queue. As far as I understand it now, a frozen process will be in the refrigerator. Thus it cannot be blocking somewhere else in kernel space. Yet we cannot be sure there's no queued IO, as theres aio. > > > On resume(): > > > = > > > 1. Don't worry about TASK_UNINTERRUPTIBLE > > > 2. Do not restart IO that may call wake_up_interruptible() > > > = > > > When do we restart such IO? > > = > > We reuse signal handling code to do that for us. It is same situation > > as when someone signals task doing I/O. > = > Again you misunderstood the question. The driver must start queued I/O > when its resume() method is called. It should then be okay for the driver > to call wake_up_interruptible(), even before tasks are unfrozen. Isn't there some code in usbfs that'll do homegrown aio and deliver a signal to a process if io is completed? Regards Oliver From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030221AbXAaQMz (ORCPT ); Wed, 31 Jan 2007 11:12:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030225AbXAaQMz (ORCPT ); Wed, 31 Jan 2007 11:12:55 -0500 Received: from mo-p00-ob.rzone.de ([81.169.146.160]:20110 "EHLO mo-p00-ob.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030221AbXAaQMy (ORCPT ); Wed, 31 Jan 2007 11:12:54 -0500 Date: Wed, 31 Jan 2007 17:12:51 +0100 (MET) From: Oliver Neukum To: Alan Stern Subject: Re: [linux-pm] question on resume() User-Agent: KMail/1.9.1 Cc: Pavel Machek , "Rafael J. Wysocki" , pm list , linux-kernel@vger.kernel.org References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200701311713.04104.oliver@neukum.org> X-RZG-AUTH: kN+qSWxTQH+Xqix8Cni7tCsVYhPCm1GP Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Am Mittwoch, 31. Januar 2007 16:54 schrieb Alan Stern: > On Wed, 31 Jan 2007, Pavel Machek wrote: > > "cease IO"? No, I believe it is enough not to start new I/O. Userspace > > is frozen at that point, it can't ask you to do I/O. > > There may be I/O requests sitting in a queue, already submitted by > userspace. The suspend method should wait for existing I/O to complete > and stop processing new entries from the queue. As far as I understand it now, a frozen process will be in the refrigerator. Thus it cannot be blocking somewhere else in kernel space. Yet we cannot be sure there's no queued IO, as theres aio. > > > On resume(): > > > > > > 1. Don't worry about TASK_UNINTERRUPTIBLE > > > 2. Do not restart IO that may call wake_up_interruptible() > > > > > > When do we restart such IO? > > > > We reuse signal handling code to do that for us. It is same situation > > as when someone signals task doing I/O. > > Again you misunderstood the question. The driver must start queued I/O > when its resume() method is called. It should then be okay for the driver > to call wake_up_interruptible(), even before tasks are unfrozen. Isn't there some code in usbfs that'll do homegrown aio and deliver a signal to a process if io is completed? Regards Oliver