From: Heiko Carstens <heiko.carstens@de.ibm.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Tejun Heo <tj@kernel.org>,
"linux-kernel@vger.kernel.org >> Linux Kernel Mailing List"
<linux-kernel@vger.kernel.org>,
linux-s390 <linux-s390@vger.kernel.org>,
KVM list <kvm@vger.kernel.org>, Oleg Nesterov <oleg@redhat.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: regression 4.4: deadlock in with cgroup percpu_rwsem
Date: Tue, 19 Jan 2016 10:55:18 +0100 [thread overview]
Message-ID: <20160119095518.GC3528@osiris> (raw)
In-Reply-To: <569D3370.6040503@de.ibm.com>
On Mon, Jan 18, 2016 at 07:48:16PM +0100, Christian Borntraeger wrote:
> 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.
Did the owner field show to something that still looks like a task_struct?
next prev parent reply other threads:[~2016-01-19 9:55 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-14 11:19 regression 4.4: deadlock in with cgroup percpu_rwsem Christian Borntraeger
2016-01-14 13:38 ` Christian Borntraeger
2016-01-14 14:04 ` Nikolay Borisov
2016-01-14 14:08 ` Christian Borntraeger
2016-01-14 14:27 ` Nikolay Borisov
2016-01-14 17:15 ` Christian Borntraeger
2016-01-14 19:56 ` Tejun Heo
2016-01-15 7:30 ` Christian Borntraeger
2016-01-15 15:13 ` Christian Borntraeger
2016-01-18 18:32 ` Peter Zijlstra
2016-01-18 18:48 ` Christian Borntraeger
2016-01-19 9:55 ` Heiko Carstens [this message]
2016-01-19 19:36 ` Christian Borntraeger
2016-01-19 19:38 ` Tejun Heo
2016-01-20 7:07 ` Heiko Carstens
2016-01-20 10:15 ` Christian Borntraeger
2016-01-20 10:30 ` Peter Zijlstra
2016-01-20 10:47 ` Peter Zijlstra
2016-01-20 15:30 ` Tejun Heo
2016-01-20 16:04 ` Tejun Heo
2016-01-20 16:49 ` Peter Zijlstra
2016-01-20 16:56 ` Tejun Heo
2016-01-23 2:03 ` Paul E. McKenney
2016-01-25 8:49 ` Christoph Hellwig
2016-01-25 19:38 ` Tejun Heo
2016-01-26 14:51 ` Christoph Hellwig
2016-01-26 15:28 ` Tejun Heo
2016-01-26 16:41 ` Christoph Hellwig
2016-01-20 10:53 ` Peter Zijlstra
2016-01-21 8:23 ` Christian Borntraeger
2016-01-21 9:27 ` Peter Zijlstra
2016-01-15 16:40 ` Tejun Heo
2016-01-19 17:18 ` [PATCH cgroup/for-4.5-fixes] cpuset: make mm migration asynchronous Tejun Heo
2016-01-22 14:24 ` Christian Borntraeger
2016-01-22 15:22 ` Tejun Heo
2016-01-22 15:45 ` Christian Borntraeger
2016-01-22 15:47 ` Tejun Heo
2016-01-22 15:23 ` Tejun Heo
2016-01-21 20:31 ` [PATCH 1/2] cgroup: make sure a parent css isn't offlined before its children Tejun Heo
2016-01-21 20:32 ` [PATCH 2/2] cgroup: make sure a parent css isn't freed " Tejun Heo
2016-01-22 15:45 ` [PATCH v2 " Tejun Heo
2016-01-21 21:24 ` [PATCH 1/2] cgroup: make sure a parent css isn't offlined " Peter Zijlstra
2016-01-21 21:28 ` Tejun Heo
2016-01-22 8:18 ` Christian Borntraeger
2016-02-29 11:13 ` [tip:sched/core] sched/cgroup: Fix cgroup entity load tracking tear-down tip-bot for Peter Zijlstra
2016-01-22 15:45 ` [PATCH v2 1/2] cgroup: make sure a parent css isn't offlined before its children Tejun Heo
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