linux-kernel - Re: [PATCH] lib: fix data race in rhashtable_rehash

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Message-ID: <CACT4Y+br2-Td8GF=eJh0SE+b1izgHy4w0btVy4JjAtuuyfAR1Q@mail.gmail.com>
Date:	Tue, 22 Sep 2015 10:52:48 +0200
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Thomas Graf <tgraf@...g.ch>
Cc:	Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	Kostya Serebryany <kcc@...gle.com>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	ktsan@...glegroups.com, Paul McKenney <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH] lib: fix data race in rhashtable_rehash_one

On Tue, Sep 22, 2015 at 10:19 AM, Thomas Graf <tgraf@...g.ch> wrote:
> On 09/21/15 at 04:03pm, Eric Dumazet wrote:
>> What I said is :
>>
>> In @head you already have the correct nulls value, from hash table.
>>
>> You do not need to recompute this value, and/or test if hash table chain
>> is empty.
>>
>> If hash bucket is empty, it contains the appropriate NULLS value.
>>
>> If you are paranoiac add this debugging check :
>>
>> if (rht_is_a_nulls(head))
>>     BUG_ON(head != (struct rhash_head *)rht_marker(ht, new_hash));
>>
>>
>> Therefore, simply fix the bug and unnecessary code with :
>
> You are absolutely right Eric. Do you want to revise your patch Dmitry?
> Eric's proposed fix absolutely the best way to fix this.

Mailed v2 of the patch.

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Dmitry Vyukov, Software Engineer, dvyukov@...gle.com
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