Messages in this thread | | | Date | Wed, 30 Mar 2016 15:15:21 +0200 | From | Peter Zijlstra <> | Subject | Re: [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260 |
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On Wed, Mar 30, 2016 at 02:46:36PM +0200, Sedat Dilek wrote: > dependency chain hlocks: 49608 [max: 327680]
OK, so that is still below the u16 limit, so you're seeing an actual hash collision and my patch will not cure that.
A different hash function _might_ help, but eventually this is an unfixable problem. Our input space is (2^13)^48 = 2^(13*48) = 2^624 = ff'n huge, reducing that to 2^64 is bound to generate a collision at some point.
[ technically the 48 held_lock spots are not fully independent, so (2^13)^48 is slightly overestimating it, but the numbers are big enough for this to not matter much. ]
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