Re: rcu_prempt stalls / lockup
From: Dave Jones
Date: Wed Apr 02 2014 - 18:49:00 EST
On Wed, Apr 02, 2014 at 09:20:43AM -0700, Paul E. McKenney wrote:
> On Tue, Apr 01, 2014 at 11:32:45AM -0700, Paul E. McKenney wrote:
> > On Tue, Apr 01, 2014 at 02:04:14PM -0400, Dave Jones wrote:
> > > On Tue, Apr 01, 2014 at 10:55:45AM -0700, Paul E. McKenney wrote:
> [ . . . ]
> > > > Waiting uninterruptibly. Presumably blocked on mutex_lock(). But
> > > > you have CONFIG_PROVE_LOCKING(), so any deadlocks should have been
> > > > reported.
> > >
> > > Lockdep had reported something a little earlier (timestamped at 1108.xxxxxx)
> > > but that's a known false-positive in xfs.
> > Yep, I would be very surprised if that was related to the grace-period hang.
> Ah, but it could be suppressing later lockdep splats. So if this can be
> reproduced without xfs, we might get additional information from lockdep.
$ git bisect bad
The merge base 5cb480f6b488128140c940abff3c36f524a334a8 is bad.
This means the bug has been fixed between 5cb480f6b488128140c940abff3c36f524a334a8 and [455c6fdbd219161bd09b1165f11699d6d73de11c 62c206bd514600d4d73751ade00dca8e488390a3 e086481baf9d0436bdd6e9b739bfa4a83fb89ef5].
Not sure where to go from here..
The 'good' news is I can reproduce it pretty reliably now.
I start my fuzz tester, and immediately do a git diff in my working tree,
and then boom..
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