Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030235AbXAaQ1O (ORCPT ); Wed, 31 Jan 2007 11:27:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030238AbXAaQ1O (ORCPT ); Wed, 31 Jan 2007 11:27:14 -0500 Received: from iolanthe.rowland.org ([192.131.102.54]:47188 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1030235AbXAaQ1N (ORCPT ); Wed, 31 Jan 2007 11:27:13 -0500 Date: Wed, 31 Jan 2007 11:27:12 -0500 (EST) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Oliver Neukum cc: Pavel Machek , "Rafael J. Wysocki" , pm list , Subject: Re: [linux-pm] question on resume() In-Reply-To: <200701311713.04104.oliver@neukum.org> 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: 1894 Lines: 46 On Wed, 31 Jan 2007, Oliver Neukum wrote: > 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. Or the driver may maintain its own I/O queue, like the HID driver does. > > > > 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? That's right. There's also code in the hub driver to call wake_up() on the khubd thread when certain I/O operations complete; nevertheless khubd _should_ remain frozen along with all the other tasks. 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/