Messages in this thread | | | Subject | Re: [PATCH] IB/uverbs: Fix lockdep warning when QP is created with 2 CQs | From | Arjan van de Ven <> | Date | Wed, 16 Aug 2006 19:11:23 +0200 |
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On Wed, 2006-08-16 at 09:43 -0700, Roland Dreier wrote: > Arjan, here's a case that disproves your rule of thumb that rwsems > are equivalent to mutexes as far as correctness goes: you can't have > an AB-BA deadlock with nested rwsems when using down_read(). In other > words, the following: > > down_read(&lock_1); > down_read(&lock_2); > down_read(&lock_2); > down_read(&lock_1); > > is perfectly safe
it's safe as long as you never ever do a down_write nested inside or outside a down_read of any of these locks....
-- if you want to mail me at work (you don't), use arjan (at) linux.intel.com
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