Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753072Ab3GWAmx (ORCPT ); Mon, 22 Jul 2013 20:42:53 -0400 Received: from mail-ob0-f171.google.com ([209.85.214.171]:60227 "EHLO mail-ob0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751717Ab3GWAmu (ORCPT ); Mon, 22 Jul 2013 20:42:50 -0400 MIME-Version: 1.0 In-Reply-To: References: <1367884221-20462-1-git-send-email-ccross@android.com> <1367884221-20462-14-git-send-email-ccross@android.com> <20130723010250.5a3465ec@xenia.leun.net> Date: Mon, 22 Jul 2013 17:42:49 -0700 X-Google-Sender-Auth: s8SCauyLOJMPE0UIhjxogzveGRM Message-ID: Subject: Re: 3.11-rc regression bisected: s2disk does not work (was Re: [PATCH v3 13/16] futex: use freezable blocking call) From: Colin Cross To: Linus Torvalds Cc: Michael Leun , lkml , Pavel Machek , "Rafael J. Wysocki" , Peter Zijlstra , Ingo Molnar , Andrew Morton , Mandeep Singh Baines , Oleg Nesterov , linux-nfs , Linux PM list , netdev , Tejun Heo , Darren Hart , Thomas Gleixner , Randy Dunlap , Al Viro Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1648 Lines: 36 On Mon, Jul 22, 2013 at 5:32 PM, Linus Torvalds wrote: > On Mon, Jul 22, 2013 at 4:55 PM, Colin Cross wrote: >> >> I think the right solution is to add a flag to the freezing task that >> marks it unfreezable. I think PF_NOFREEZE would work, although it is >> normally used on kernel threads, can you see if the attached patch >> helps? > > Hmm. That does seem to be the right thing to do, but I wonder about > the *other* callers of freeze_processes() IOW, kexec and friends. > > So maybe we should do this in {freeze|thaw}_processes() itself, and > just make the rule be that the caller of freeze_processes() itself is > obviously not frozen, and has to be the same one that then thaws > things? > > Colin? Rafael? Comments? > > Linus I was worried about clearing the flag in thaw_processes(). If a kernel thread with PF_NOFREEZE set ever called thaw_processes(), which autosleep might do, it would clear the flag. Or if a different thread called freeze_processes() and thaw_processes(). All the other callers besides the SNAPSHOT_FREEZE ioctl stay in the kernel between freeze_processes() and thaw_processes(), which makes the fanout of places that could call try_to_freeze() much more controllable. Using a new flag that operates like PF_NOFREEZE but doesn't conflict with it, or a nofreeze_depth counter, would also work. -- 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/