From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752647Ab2GZUK6 (ORCPT ); Thu, 26 Jul 2012 16:10:58 -0400 Received: from ogre.sisk.pl ([193.178.161.156]:59068 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752043Ab2GZUK5 (ORCPT ); Thu, 26 Jul 2012 16:10:57 -0400 From: "Rafael J. Wysocki" To: Colin Cross Subject: Re: [PATCH] cpuidle: coupled: fix sleeping while atomic in cpu notifier Date: Thu, 26 Jul 2012 22:16:43 +0200 User-Agent: KMail/1.13.6 (Linux/3.5.0+; KDE/4.6.0; x86_64; ; ) Cc: Len Brown , Len Brown , Kevin Hilman , Santosh Shilimkar , linux-kernel@vger.kernel.org, Linux PM list References: <1343251216-24106-1-git-send-email-ccross@android.com> <201207262215.06372.rjw@sisk.pl> In-Reply-To: <201207262215.06372.rjw@sisk.pl> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201207262216.43665.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday, July 26, 2012, Rafael J. Wysocki wrote: > On Thursday, July 26, 2012, Colin Cross wrote: > > On Thu, Jul 26, 2012 at 12:55 PM, Rafael J. Wysocki wrote: > > > On Wednesday, July 25, 2012, Colin Cross wrote: > > >> The cpu hotplug notifier gets called in both atomic and non-atomic > > >> contexts, it is not always safe to lock a mutex. Filter out all events > > >> except the six necessary ones, which are all sleepable, before taking > > >> the mutex. > > > > > > I wonder what mutual exclusion mechanis we rely on when the mutex is not taken? > > > > We don't need any mutual exclusion because the notifier returns immediately. > > Don't we need to disable preemption even? Sorry, scratch that. It returns NOTIFY_OK if we're not going to take the mutex. Thanks, Rafael