Messages in this thread | | | Subject | Re: [PATCH] Increase lockdep MAX_LOCK_DEPTH | From | Peter Zijlstra <> | Date | Fri, 31 Aug 2007 17:09:21 +0200 |
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On Sat, 2007-09-01 at 01:05 +1000, David Chinner wrote:
> > Trouble is, we'd like to have a sane upper bound on the amount of held > > locks at any one time, obviously this is just wanting, because a lot of > > lock chains also depend on the number of online cpus... > > Sure - this is an obvious case where it is valid to take >30 locks at > once in a single thread. In fact, worst case here we are taking twice this > number of locks - we actually take 2 per inode (ilock and flock) so a > full 32 inode cluster free would take >60 locks in the middle of this > function and we should be busting this depth couter limit all the > time.
I think this started because jeffpc couldn't boot without XFS busting lockdep :-)
> Do semaphores (the flush locks) contribute to the lock depth > counters?
No, alas, we cannot handle semaphores in lockdep. Semaphores don't have a strict owner, hence we cannot track them. This is one of the reasons to rid ourselves of semaphores - that and there are very few cases where the actual semantics of semaphores are needed. Most of the times code using semaphores can be expressed with either a mutex or a completion.
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