Re: [PATCH] Increase lockdep MAX_LOCK_DEPTH

[Eric Sandeen <sandeen@sandeen.net>]

Peter Zijlstra wrote:
> 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.

That explains why 40 was enough for me, I guess :)

-Eric