From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761496AbXGEN2c (ORCPT ); Thu, 5 Jul 2007 09:28:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758663AbXGEN2Z (ORCPT ); Thu, 5 Jul 2007 09:28:25 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:53526 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756146AbXGEN2Y (ORCPT ); Thu, 5 Jul 2007 09:28:24 -0400 From: "Rafael J. Wysocki" To: nigel@suspend2.net Subject: Re: [PATCH] Remove process freezer from suspend to RAM pathway Date: Thu, 5 Jul 2007 15:35:45 +0200 User-Agent: KMail/1.9.5 Cc: Pavel Machek , Oliver Neukum , Miklos Szeredi , benh@kernel.crashing.org, mjg59@srcf.ucam.org, linux-kernel@vger.kernel.org, linux-pm@lists.linux-foundation.org References: <20070703042916.GA17240@srcf.ucam.org> <200707051425.07904.rjw@sisk.pl> <200707052238.27889.nigel@nigel.suspend2.net> In-Reply-To: <200707052238.27889.nigel@nigel.suspend2.net> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200707051535.46196.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thursday, 5 July 2007 14:38, Nigel Cunningham wrote: > Hi. > > On Thursday 05 July 2007 22:25:06 Rafael J. Wysocki wrote: > > On Thursday, 5 July 2007 01:45, Pavel Machek wrote: > > > On Tue 2007-07-03 21:32:20, Oliver Neukum wrote: > > > > Am Dienstag, 3. Juli 2007 schrieb Miklos Szeredi: > > > > > > And a further question. The freezer is not atomic. What do you do > > > > > > if a task not yet frozen calls sys_sync(), but fuse is already > frozen? > > > > > > > > > > What do you do if a task not yet frozen writes to a pipe, on the other > > > > > end of which is a task already frozen? > > > > > > There's some difference between uninterruptible and interruptible > > > sleep I'd say. > > > > > > > > It doesn't matter. The only thing that should matter during suspend > > > > > (not hibernate) is saving the state of devices to ram, and putting the > > > > > devices to sleep. > > > > > > > > Well, but you did remove sys_sync() from the freezer, which is > > > > and must be called in the hibernate path. > > > > > > Not "must". In fact, hibernation should be safe without sys_sync(). It > > > is just user un-friendly. > > > > In fact, I'd like to remove the sys_sync() from the freezer entirely, > because > > it just doesn't belong in there. > > > > The only advantege of having sys_sync() in freeze_processes() is that we > > have a chance to write out everything when applications cannot produce more > > data to write, but there are filesystems which don't do that anyway (eg. > XFS), > > so generally there's no reason to bother. > > Shouldn't XFS - and fuse - be considered to be broken? Sync should sync data > and if XFS isn't doing that, it's wrong. > > In the case of fuse, we should have a mechanism by which fuse processes can be > made to sync if they do have any pending I/O, and by which they can be frozen > later than other userspace processes. > > I'd like to see the sync stay, because it improves reliability and data > integrity in the fail-to-resume case. Calling scripts would probably invoke > sync themselves if they don't already, but that's racy. As it is at the > moment, we know userspace is stopped, so syncing isn't racy. I'd like to move the sync out of the freezer, but to call it from the suspend/hibernation code, so that we do sys_sync(); error = freeze_processes(); etc. Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth