From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754176Ab1KDAWA (ORCPT ); Thu, 3 Nov 2011 20:22:00 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:49969 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753993Ab1KDAV6 (ORCPT ); Thu, 3 Nov 2011 20:21:58 -0400 From: "Rafael J. Wysocki" To: Tejun Heo Subject: Re: [PATCH pm-for-3.2 2/2] freezer: revert 27920651fe "PM / Freezer: Make fake_signal_wake_up() wake TASK_KILLABLE tasks too" Date: Fri, 4 Nov 2011 01:24:33 +0100 User-Agent: KMail/1.13.6 (Linux/3.1.0-rc10+; KDE/4.6.0; x86_64; ; ) Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Oleg Nesterov , Jeff Layton References: <20111103230749.GS4417@google.com> <201111040113.21514.rjw@sisk.pl> <20111104001759.GU4417@google.com> In-Reply-To: <20111104001759.GU4417@google.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201111040124.34015.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday, November 04, 2011, Tejun Heo wrote: > Hello, Rafael. > > On Fri, Nov 04, 2011 at 01:13:21AM +0100, Rafael J. Wysocki wrote: > > On Friday, November 04, 2011, Tejun Heo wrote: > > > Commit 27920651fe "PM / Freezer: Make fake_signal_wake_up() wake > > > TASK_KILLABLE tasks too" updated fake_signal_wake_up() used by freezer > > > to wake up KILLABLE tasks. Sending unsolicited wakeups to tasks in > > > killable sleep is dangerous as there are code paths which depend on > > > tasks not waking up spuriously from KILLABLE sleep. > > > > > > For example. sys_read() or page can sleep in TASK_KILLABLE assuming > > > that wait/down/whatever _killable can only fail if we can not return > > > to the usermode. TASK_TRACED is another obvious example. > > > > > > The previous patch updated wait_event_freezekillable() such that it > > > doesn't depend on the spurious wakeup. This patch reverts the > > > offending commit. > > > > > > Note that the spurious KILLABLE wakeup had other implicit effects in > > > KILLABLE sleeps in nfs and cifs and those will need further updates to > > > regain freezekillable behavior. > > > > > > Signed-off-by: Tejun Heo > > > Cc: Jeff Layton > > > LKML-Reference: <20111031221743.GA18855@google.com> > > > > Applied to linux-pm/linux-next. > > Just to be sure, as the commit which changed fake_signal_wake_up() to > use KILLABLE wakeup is already mainline, these two will have to be > pushed as fixes after some time in this devel cycle. Yes, they are 3.2 material and I'm going to push them in the next few days along with a number of other PM-related fixes/cleanups. Is that OK? Rafael