Re: 3.14.0+/x86: lockdep and mutexes not getting along

From: Dave Jones
Date: Thu Apr 10 2014 - 19:32:34 EST


On Thu, Apr 10, 2014 at 07:26:52PM -0400, Dave Jones wrote:
> On Thu, Apr 10, 2014 at 10:14:44AM -0700, Jason Low wrote:
> > On Thu, 2014-04-10 at 11:18 +0200, Peter Zijlstra wrote:
> > > On Wed, Apr 09, 2014 at 10:42:59PM -0700, Jason Low wrote:
> > > > As a starting point, would either of you like to test the following
> > > > patch to see if it fixes the issue? This patch essentially generates the
> > > > same code as in older kernels in the debug case. This applies on top of
> > > > kernels with both commits 6f008e72cd11 and 1d8fe7dc8078.
> > >
> > >
> > > So I managed to reproduce, and the below makes it go away. I just don't
> > > understand why though. will stare more.
> >
> > So one thing I noticed that is different in the current code is that in
> > debug_mutex_unlock(), there is is a possibility that it does not unlock
> > the mutex (when !debug_locks). May be interesting to try out this
> > patch too:
>
> I've been seeing lockups this last week or two too, that manifested by
> RCU spewing stall messages, and the box being totally unresponsive.
> This patch seems to cure that for me, which I'm sure will make Paul
> happy to hear.

duh, replied to the wrong mail. I tested peterz's last patch, not Jason's.

Dave

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