linux-kernel - Re: [PATCH v5 04/18] slab: don't preemptively remove element from list in cache destroy

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Message-ID: <50881500.9030604@parallels.com>
Date:	Wed, 24 Oct 2012 20:19:12 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Pekka Enberg <penberg@...nel.org>
CC:	Christoph Lameter <cl@...ux.com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>, <cgroups@...r.kernel.org>,
	Mel Gorman <mgorman@...e.de>, Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	<kamezawa.hiroyu@...fujitsu.com>,
	David Rientjes <rientjes@...gle.com>, <devel@...nvz.org>,
	Suleiman Souhlal <suleiman@...gle.com>
Subject: Re: [PATCH v5 04/18] slab: don't preemptively remove element from
 list in cache destroy

On 10/24/2012 10:54 AM, Pekka Enberg wrote:
> On Mon, Oct 22, 2012 at 11:40 AM, Glauber Costa <glommer@...allels.com> wrote:
>> On 10/19/2012 11:34 PM, Christoph Lameter wrote:
>>> On Fri, 19 Oct 2012, Glauber Costa wrote:
>>>
>>>> I, however, see no reason why we need to do so, since we are now locked
>>>> during the whole deletion (which wasn't necessarily true before).  I
>>>> propose a simplification in which we delete it only when there is no
>>>> more going back, so we don't need to add it again.
>>>
>>> Ok lets hope that holding the lock does not cause issues.
>>>
>>> Acked-by: Christoph Lameter <cl@...ux.com>
>>>
>> BTW: One of the good things about this set, is that we are naturally
>> exercising cache destruction a lot more than we did before. So if there
>> is any problem, either with this or anything related to cache
>> destruction, it should at least show up a lot more frequently. So far,
>> this does not seem to cause any problems.
> 
> We no longer hold the mutex the whole time after. See commit 210ed9d
> ("mm, slab: release slab_mutex earlier in kmem_cache_destroy()") for
> details.
> 
I will resubmit then.

It doesn't really change the spirit of the patch. I took a look at that
fix, and what it does, is it releases the mutex right after
kmem_cache_shutdown() succeeds. Removing from the list in there would do
the trick.

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