From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752175Ab2APFx6 (ORCPT ); Mon, 16 Jan 2012 00:53:58 -0500 Received: from mga03.intel.com ([143.182.124.21]:10110 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751074Ab2APFx5 (ORCPT ); Mon, 16 Jan 2012 00:53:57 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="scan'208";a="96197732" Date: Mon, 16 Jan 2012 13:53:54 +0800 From: Wu Fengguang To: Chanho Min Cc: Rabin Vincent , Jens Axboe , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/backing-dev.c: fix crash when USB/SCSI device is detached Message-ID: <20120116055354.GA15265@localhost> References: <20120115125853.GA9234@localhost> <20120115153838.GA4279@debian> <20120116025331.GA16516@localhost> <20120116055044.GA14857@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20120116055044.GA14857@localhost> 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 On Mon, Jan 16, 2012 at 01:50:44PM +0800, Wu Fengguang wrote: > On Mon, Jan 16, 2012 at 02:28:30PM +0900, Chanho Min wrote: > > On Mon, Jan 16, 2012 at 11:53 AM, Wu Fengguang wrote: > > > On Sun, Jan 15, 2012 at 09:11:07PM +0530, Rabin Vincent wrote: > > >> On Sun, Jan 15, 2012 at 08:58:53PM +0800, Wu Fengguang wrote: > > >> > On Sun, Jan 15, 2012 at 03:58:43PM +0530, Rabin Vincent wrote: > > >> > > diff --git a/mm/backing-dev.c b/mm/backing-dev.c > > >> > > index 71034f4..a39ad70 100644 > > >> > > --- a/mm/backing-dev.c > > >> > > +++ b/mm/backing-dev.c > > >> > > @@ -318,7 +318,7 @@ static void wakeup_timer_fn(unsigned long data) > > >> > >   if (bdi->wb.task) { > > >> > >           trace_writeback_wake_thread(bdi); > > >> > >           wake_up_process(bdi->wb.task); > > >> > > - } else { > > >> > > + } else if (bdi->dev) { > > >> > >           /* > > >> > >            * When bdi tasks are inactive for long time, they are killed. > > >> > >            * In this case we have to wake-up the forker thread which > > >> > > @@ -584,6 +584,8 @@ EXPORT_SYMBOL(bdi_register_dev); > > >> > >   */ > > >> > >  static void bdi_wb_shutdown(struct backing_dev_info *bdi) > > >> > >  { > > >> > > + struct task_struct *task = NULL; > > > > Thanks, I fully understand. > > In addition, Would not bdi_wakeup_flusher also be fixed? > > Yes, indeed! But wait.. Rabin's patch actually fixes the NULL deference in the call trace_writeback_wake_forker_thread(bdi); The wakeup of the forker thread should be harmless. Thanks, Fengguang > > >From dc7d4e86911c0a7ea35043485b04e8a09aa74ffd Mon Sep 17 00:00:00 2001 > > From: Chanho Min > > Date: Mon, 16 Jan 2012 14:14:48 +0900 > > Subject: [PATCH] backing-dev: add for 'fix wakeup timer races with > > bdi_unregister()' > > > > Signed-off-by: Chanho Min > > --- > > fs/fs-writeback.c | 2 +- > > 1 files changed, 1 insertions(+), 1 deletions(-) > > > > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c > > index f855916..ee40833 100644 > > --- a/fs/fs-writeback.c > > +++ b/fs/fs-writeback.c > > @@ -97,7 +97,7 @@ static void bdi_wakeup_flusher(struct backing_dev_info *bdi) > > { > > if (bdi->wb.task) { > > wake_up_process(bdi->wb.task); > > - } else { > > + } else if (bdi->dev) { > > /* > > * The bdi thread isn't there, wake up the forker thread which > > * will create and run it. > > -- > > 1.7.0.4