Messages in this thread |  | | Date | Fri, 04 Dec 2015 14:38:44 -0500 (EST) | | Subject | Re: rhashtable: Prevent spurious EBUSY errors on insertion | | From | David Miller <> |
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From: Herbert Xu <herbert@gondor.apana.org.au> Date: Thu, 3 Dec 2015 20:41:29 +0800
> Thomas and Phil observed that under stress rhashtable insertion > sometimes failed with EBUSY, even though this error should only > ever been seen when we're under attack and our hash chain length > has grown to an unacceptable level, even after a rehash. > > It turns out that the logic for detecting whether there is an > existing rehash is faulty. In particular, when two threads both > try to grow the same table at the same time, one of them may see > the newly grown table and thus erroneously conclude that it had > been rehashed. This is what leads to the EBUSY error. > > This patch fixes this by remembering the current last table we > used during insertion so that rhashtable_insert_rehash can detect > when another thread has also done a resize/rehash. When this is > detected we will give up our resize/rehash and simply retry the > insertion with the new table. > > Reported-by: Thomas Graf <tgraf@suug.ch> > Reported-by: Phil Sutter <phil@nwl.cc> > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Looks good, applied, thanks Herbert.
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