From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754130Ab1KDASH (ORCPT ); Thu, 3 Nov 2011 20:18:07 -0400 Received: from mail-gy0-f174.google.com ([209.85.160.174]:57861 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753123Ab1KDASF (ORCPT ); Thu, 3 Nov 2011 20:18:05 -0400 Date: Thu, 3 Nov 2011 17:17:59 -0700 From: Tejun Heo To: "Rafael J. Wysocki" Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Oleg Nesterov , Jeff Layton Subject: Re: [PATCH pm-for-3.2 2/2] freezer: revert 27920651fe "PM / Freezer: Make fake_signal_wake_up() wake TASK_KILLABLE tasks too" Message-ID: <20111104001759.GU4417@google.com> References: <20111103230749.GS4417@google.com> <20111103230910.GT4417@google.com> <201111040113.21514.rjw@sisk.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201111040113.21514.rjw@sisk.pl> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Thanks. -- tejun