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Re: regression 4.4: deadlock in with cgroup percpu_rwsem

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: regression 4.4: deadlock in with cgroup percpu_rwsem
Date 2016-01-18 19:40 +0100
Message-ID <qSmSC-4zc-17@gated-at.bofh.it> (permalink)
References <qQOgi-6eV-7@gated-at.bofh.it> <qQWdP-3jT-7@gated-at.bofh.it> <qR79g-2OU-11@gated-at.bofh.it> <qRekq-7Xi-21@gated-at.bofh.it>
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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.

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Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christian Borntraeger <borntraeger@de.ibm.com> - 2016-01-15 16:20 +0100
  Re: regression 4.4: deadlock in with cgroup percpu_rwsem Peter Zijlstra <peterz@infradead.org> - 2016-01-18 19:40 +0100
    Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christian Borntraeger <borntraeger@de.ibm.com> - 2016-01-18 19:50 +0100
      Re: regression 4.4: deadlock in with cgroup percpu_rwsem Heiko Carstens <heiko.carstens@de.ibm.com> - 2016-01-19 11:00 +0100
        Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christian Borntraeger <borntraeger@de.ibm.com> - 2016-01-19 20:40 +0100
          Re: regression 4.4: deadlock in with cgroup percpu_rwsem Tejun Heo <tj@kernel.org> - 2016-01-19 20:40 +0100
            Re: regression 4.4: deadlock in with cgroup percpu_rwsem Heiko Carstens <heiko.carstens@de.ibm.com> - 2016-01-20 08:10 +0100
              Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christian Borntraeger <borntraeger@de.ibm.com> - 2016-01-20 11:20 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Peter Zijlstra <peterz@infradead.org> - 2016-01-20 11:40 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Peter Zijlstra <peterz@infradead.org> - 2016-01-20 11:50 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Tejun Heo <tj@kernel.org> - 2016-01-20 16:40 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Tejun Heo <tj@kernel.org> - 2016-01-20 17:10 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Peter Zijlstra <peterz@infradead.org> - 2016-01-20 17:50 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Tejun Heo <tj@kernel.org> - 2016-01-20 18:00 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-01-23 03:10 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christoph Hellwig <hch@lst.de> - 2016-01-25 09:50 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Tejun Heo <tj@kernel.org> - 2016-01-25 20:40 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christoph Hellwig <hch@lst.de> - 2016-01-26 16:00 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Tejun Heo <tj@kernel.org> - 2016-01-26 16:30 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christoph Hellwig <hch@lst.de> - 2016-01-26 17:50 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Peter Zijlstra <peterz@infradead.org> - 2016-01-20 12:00 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Christian Borntraeger <borntraeger@de.ibm.com> - 2016-01-21 09:30 +0100
                Re: regression 4.4: deadlock in with cgroup percpu_rwsem Peter Zijlstra <peterz@infradead.org> - 2016-01-21 10:30 +0100

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