Messages in this thread | | | Subject | Re: [PATCH 1/2] lockdep: Include recursive read-locks dependencies in the tree | From | Peter Zijlstra <> | Date | Wed, 18 Nov 2009 11:26:05 +0100 |
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On Wed, 2009-11-18 at 02:06 +0100, Frederic Weisbecker wrote: > Currently, recursive read locks are checked in two ways: > > - walk through the locks held by the current task and check possible > deadlock. > > - if the recursive read lock is not already present in the lock held > by the current task, check its dependencies against the tree. > > But this recursive read lock will never be added to the tree of > dependencies. It means that the following sequence: > > A = rwlock (Ar: taken as read recursive, Aw: taken as write) > B = normal lock > > Ar -> B > B -> Aw > > won't ever be detected as a lock inversion. > This patch fixes it by inserting the recursive read locks into the > tree of dependencies and enhancing the circular checks (check the > class and the read attribute collision).
There were some very funny corner cases with IRQ state vs recursive locks, I don't seen any of that mentioned here.
Bot ego and I poked at it at various times, but neither of us managed to actually finish it due to getting distracted with other bits I guess.
http://programming.kicks-ass.net/kernel-patches/cpu-hotplug/
http://lkml.org/lkml/2009/5/11/203
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