Messages in this thread | | | Date | Thu, 19 Nov 2009 17:07:02 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 1/2] lockdep: Include recursive read-locks dependencies in the tree |
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On Wed, Nov 18, 2009 at 11:26:05AM +0100, Peter Zijlstra wrote: > 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.
Ah right. I forgot these cases... I probably need to do some other checks in check_usage().
I'll have a look at it.
Thanks.
> 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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