Re: [PATCH v2] lib: fix data race in rhashtable_rehash_one

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From	Eric Dumazet <eric.dumazet@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] lib: fix data race in rhashtable_rehash_one
Date	Tue, 22 Sep 2015 11:10:02 +0200
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On Tue, 2015-09-22 at 10:51 +0200, Dmitry Vyukov wrote:
> rhashtable_rehash_one() uses complex logic to update entry->next field,
> after INIT_RHT_NULLS_HEAD and NULLS_MARKER expansion:
> 
> entry->next = 1 | ((base + off) << 1)
> 
> This can be compiled along the lines of:
> 
> entry->next = base + off
> entry->next <<= 1
> entry->next |= 1
> 
> Which will break concurrent readers.
> 
> NULLS value recomputation is not needed here, so just remove
> the complex logic.
> 
> The data race was found with KernelThreadSanitizer (KTSAN).
> 
> Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
> ---

Thanks Dmitry

Acked-by: Eric Dumazet <edumazet@google.com>


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Thread

[PATCH v2] lib: fix data race in rhashtable_rehash_one Dmitry Vyukov <dvyukov@google.com> - 2015-09-22 11:00 +0200
  Re: [PATCH v2] lib: fix data race in rhashtable_rehash_one Eric Dumazet <eric.dumazet@gmail.com> - 2015-09-22 11:10 +0200
  Re: [PATCH v2] lib: fix data race in rhashtable_rehash_one Thomas Graf <tgraf@suug.ch> - 2015-09-22 11:20 +0200
  Re: [PATCH v2] lib: fix data race in rhashtable_rehash_one Herbert Xu <herbert@gondor.apana.org.au> - 2015-09-22 17:30 +0200
  Re: [PATCH v2] lib: fix data race in rhashtable_rehash_one David Miller <davem@davemloft.net> - 2015-09-23 02:40 +0200

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