Messages in this thread | | | Subject | Re: regression 4.4: deadlock in with cgroup percpu_rwsem | From | Christian Borntraeger <> | Date | Mon, 18 Jan 2016 19:48:16 +0100 |
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On 01/18/2016 07:32 PM, Peter Zijlstra wrote: > On Fri, Jan 15, 2016 at 04:13:34PM +0100, Christian Borntraeger wrote: >>> Yes, the deadlock is gone and the system is still running. >>> After some time I had the following WARN in the logs, though. >>> Not sure yet if that is related. >>> >>> [25331.763607] DEBUG_LOCKS_WARN_ON(lock->owner != current) >>> [25331.763630] ------------[ cut here ]------------ >>> [25331.763634] WARNING: at kernel/locking/mutex-debug.c:80 > >> I restarted the test with panic_on_warn. Hopefully I can get a dump to check >> which mutex this was. > > Hard to reproduce warnings like this tend to point towards memory > corruption. Someone stepped on the mutex value and tickles the sanity > check. > > With lockdep and debugging enabled the mutex gets quite a bit bigger, so > it gets more likely to be hit by 'random' corruption. > > The locking in seq_read() seems rather straight forward.
I was able to reproduce. The dump shows a mutex that has an owner field, which does not exists as a task so this all looks fishy. The good thing is, that I can reproduce the issue within some hours. (exact same backtrace). Will add some more debug data to get a handle where we come from.
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