From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760518AbXGEMii (ORCPT ); Thu, 5 Jul 2007 08:38:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757234AbXGEMia (ORCPT ); Thu, 5 Jul 2007 08:38:30 -0400 Received: from nigel.suspend2.net ([203.171.70.205]:48942 "EHLO nigel.suspend2.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757164AbXGEMia (ORCPT ); Thu, 5 Jul 2007 08:38:30 -0400 From: Nigel Cunningham Reply-To: nigel@suspend2.net To: "Rafael J. Wysocki" Subject: Re: [PATCH] Remove process freezer from suspend to RAM pathway Date: Thu, 5 Jul 2007 22:38:25 +1000 User-Agent: KMail/1.9.6 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> <20070704234523.GC2719@elf.ucw.cz> <200707051425.07904.rjw@sisk.pl> In-Reply-To: <200707051425.07904.rjw@sisk.pl> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart1201636.iSAgefnjtu"; protocol="application/pgp-signature"; micalg=pgp-sha1 Content-Transfer-Encoding: 7bit Message-Id: <200707052238.27889.nigel@nigel.suspend2.net> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org --nextPart1201636.iSAgefnjtu Content-Type: text/plain; charset="cp 850" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline 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=20 frozen? > > > >=20 > > > > What do you do if a task not yet frozen writes to a pipe, on the ot= her > > > > end of which is a task already frozen? > >=20 > > There's some difference between uninterruptible and interruptible > > sleep I'd say. > >=20 > > > > 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. > > >=20 > > > Well, but you did remove sys_sync() from the freezer, which is > > > and must be called in the hibernate path. > >=20 > > Not "must". In fact, hibernation should be safe without sys_sync(). It > > is just user un-friendly. >=20 > In fact, I'd like to remove the sys_sync() from the freezer entirely,=20 because > it just doesn't belong in there. >=20 > The only advantege of having sys_sync() in freeze_processes() is that we > have a chance to write out everything when applications cannot produce mo= re > data to write, but there are filesystems which don't do that anyway (eg.= =20 XFS), > so generally there's no reason to bother. Shouldn't XFS - and fuse - be considered to be broken? Sync should sync dat= a=20 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=20 made to sync if they do have any pending I/O, and by which they can be froz= en=20 later than other userspace processes. I'd like to see the sync stay, because it improves reliability and data=20 integrity in the fail-to-resume case. Calling scripts would probably invoke= =20 sync themselves if they don't already, but that's racy. As it is at the=20 moment, we know userspace is stopped, so syncing isn't racy. Regards, Nigel =2D-=20 See http://www.tuxonice.net for Howtos, FAQs, mailing lists, wiki and bugzilla info. --nextPart1201636.iSAgefnjtu Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQBGjOZDN0y+n1M3mo0RAk9mAKCSSal8CrEcxMwbaaxn4f4gftpzJgCg0gp9 ZszH0kVXyMj2Uy+XMSuy0Q8= =Mksm -----END PGP SIGNATURE----- --nextPart1201636.iSAgefnjtu--