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From: Andrew Morton <akpm@linux-foundation.org>
To: Kautuk Consul <consul.kautuk@gmail.com>
Cc: Jens Axboe <jaxboe@fusionio.com>,
	Wu Fengguang <fengguang.wu@intel.com>, Jan Kara <jack@suse.cz>,
	Dave Chinner <dchinner@redhat.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] mm/backing-dev.c: Call del_timer_sync instead of del_timer
Date: Thu, 1 Sep 2011 14:33:33 -0700	[thread overview]
Message-ID: <20110901143333.51baf4ae.akpm@linux-foundation.org> (raw)
In-Reply-To: <1314892622-18267-1-git-send-email-consul.kautuk@gmail.com>

On Thu,  1 Sep 2011 21:27:02 +0530
Kautuk Consul <consul.kautuk@gmail.com> wrote:

> This is important for SMP scenario, to check whether the timer
> callback is executing on another CPU when we are deleting the
> timer.
> 

I don't see why?

> index d6edf8d..754b35a 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -385,7 +385,7 @@ static int bdi_forker_thread(void *ptr)
>  		 * dirty data on the default backing_dev_info
>  		 */
>  		if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
> -			del_timer(&me->wakeup_timer);
> +			del_timer_sync(&me->wakeup_timer);
>  			wb_do_writeback(me, 0);
>  		}

It isn't a use-after-free fix: bdi_unregister() safely shoots down any
running timer.

Please completely explain what you believe the problem is here.

WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: Kautuk Consul <consul.kautuk@gmail.com>
Cc: Jens Axboe <jaxboe@fusionio.com>,
	Wu Fengguang <fengguang.wu@intel.com>, Jan Kara <jack@suse.cz>,
	Dave Chinner <dchinner@redhat.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] mm/backing-dev.c: Call del_timer_sync instead of del_timer
Date: Thu, 1 Sep 2011 14:33:33 -0700	[thread overview]
Message-ID: <20110901143333.51baf4ae.akpm@linux-foundation.org> (raw)
In-Reply-To: <1314892622-18267-1-git-send-email-consul.kautuk@gmail.com>

On Thu,  1 Sep 2011 21:27:02 +0530
Kautuk Consul <consul.kautuk@gmail.com> wrote:

> This is important for SMP scenario, to check whether the timer
> callback is executing on another CPU when we are deleting the
> timer.
> 

I don't see why?

> index d6edf8d..754b35a 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -385,7 +385,7 @@ static int bdi_forker_thread(void *ptr)
>  		 * dirty data on the default backing_dev_info
>  		 */
>  		if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
> -			del_timer(&me->wakeup_timer);
> +			del_timer_sync(&me->wakeup_timer);
>  			wb_do_writeback(me, 0);
>  		}

It isn't a use-after-free fix: bdi_unregister() safely shoots down any
running timer.

Please completely explain what you believe the problem is here.

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  reply	other threads:[~2011-09-01 21:33 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-09-01 15:57 [PATCH 1/1] mm/backing-dev.c: Call del_timer_sync instead of del_timer Kautuk Consul
2011-09-01 15:57 ` Kautuk Consul
2011-09-01 21:33 ` Andrew Morton [this message]
2011-09-01 21:33   ` Andrew Morton
2011-09-02  5:17   ` kautuk.c @samsung.com
2011-09-02  5:17     ` kautuk.c @samsung.com
2011-09-02 11:21     ` Jan Kara
2011-09-02 11:21       ` Jan Kara
2011-09-02 11:44       ` kautuk.c @samsung.com
2011-09-02 11:44         ` kautuk.c @samsung.com
2011-09-02 12:02         ` kautuk.c @samsung.com
2011-09-02 12:02           ` kautuk.c @samsung.com
2011-09-02 15:14           ` Jan Kara
2011-09-02 15:14             ` Jan Kara
2011-09-05  5:49             ` kautuk.c @samsung.com
2011-09-05  5:49               ` kautuk.c @samsung.com
2011-09-05 10:39               ` Jan Kara
2011-09-05 10:39                 ` Jan Kara
2011-09-05 14:36                 ` kautuk.c @samsung.com
2011-09-05 14:36                   ` kautuk.c @samsung.com
2011-09-05 16:05                   ` Jan Kara
2011-09-05 16:05                     ` Jan Kara
2011-09-06  4:11                     ` kautuk.c @samsung.com
2011-09-06  4:11                       ` kautuk.c @samsung.com
2011-09-06  9:14                       ` Jan Kara
2011-09-06  9:14                         ` Jan Kara

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