linux-kernel - Re: [PATCH 3/3] slub: release a lock if freeing object with a lock is failed in __slab

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Message-ID: <CAAmzW4PzJiBFDR3rKwVBn0Ex5cCR=qai6SA9_SbVH-psuh6nOQ@mail.gmail.com>
Date:	Mon, 9 Jul 2012 01:19:09 +0900
From:	JoonSoo Kim <js1304@...il.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Pekka Enberg <penberg@...nel.org>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 3/3] slub: release a lock if freeing object with a lock is
 failed in __slab_free()

2012/7/7 Christoph Lameter <cl@...ux.com>:
> On Fri, 6 Jul 2012, JoonSoo Kim wrote:
>
>> >> At CPU2, we don't need lock anymore, because this slab already in partial list.
>> >
>> > For that scenario we could also simply do a trylock there and redo
>> > the loop if we fail. But still what guarantees that another process will
>> > not modify the page struct between fetching the data and a successful
>> > trylock?
>>
>>
>> I'm not familiar with English, so take my ability to understand into
>> consideration.
>
> I have a hard time understanding what you want to accomplish here.
>
>> we don't need guarantees that another process will not modify
>> the page struct between fetching the data and a successful trylock.
>
> No we do not need that since the cmpxchg will then fail.
>
> Maybe it would be useful to split this patch into two?
>
> One where you introduce the dropping of the lock and the other where you
> get rid of certain code paths?
>

Dropping of the lock is need for getting rid of certain code paths.
So, I can't split this patch into two.

Sorry for confusing all the people.
I think that I don't explain my purpose well.
I will prepare new version in which I explain purpose of patch better.

Thanks for kind review.
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