Re: [PATCH] IB/uverbs: Fix lockdep warning when QP is created with2 CQs

From: Arjan van de Ven
Date: Wed Aug 16 2006 - 13:10:12 EST

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)

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