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Message-ID: <20150922151957.GA13278@gondor.apana.org.au> Date: Tue, 22 Sep 2015 23:19:57 +0800 From: Herbert Xu <herbert@...dor.apana.org.au> To: Dmitry Vyukov <dvyukov@...gle.com> Cc: eric.dumazet@...il.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, tgraf@...g.ch, kcc@...gle.com, andreyknvl@...gle.com, glider@...gle.com, ktsan@...glegroups.com, paulmck@...ux.vnet.ibm.com, dvyukov@...gle.com Subject: Re: [PATCH v2] lib: fix data race in rhashtable_rehash_one Dmitry Vyukov <dvyukov@...gle.com> 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@...gle.com> Acked-by: Herbert Xu <herbert@...dor.apana.org.au> -- Email: Herbert Xu <herbert@...dor.apana.org.au> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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