From mboxrd@z Thu Jan  1 00:00:00 1970
From: Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [rfc patch] fs,reiserfs: unlock superblock before callling
 reiserfs_quota_on_mount()
Date: Tue, 14 Aug 2012 13:44:33 -0400
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Cc: Thomas Gleixner <tglx@linutronix.de>,
	"linux-rt-users@vger.kernel.org" <linux-rt-users@vger.kernel.org>,
	Frederic Weisbecker <fweisbec@gmail.com>,
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To: Mike Galbraith <efault@gmx.de>
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On Tue, 2012-08-14 at 19:26 +0200, Mike Galbraith wrote:
> On Tue, 2012-08-14 at 17:18 +0200, Thomas Gleixner wrote: 
> > On Tue, 14 Aug 2012, Mike Galbraith wrote:
> > 
> > > On Tue, 2012-08-14 at 16:39 +0200, Mike Galbraith wrote: 
> > > > On Tue, 2012-08-14 at 10:23 -0400, Steven Rostedt wrote: 
> > > > > On Tue, 2012-08-14 at 15:06 +0200, Mike Galbraith wrote:
> > > > > > Greetings,
> > > > > > 
> > > > > > Using openSUSE's "partitioner" gizmo to set up a reiserfs partition with
> > > > > > quotas and whatnot enabled rewarded me with a deadlock.
> > > > > 
> > > > > Is this just a -rt bug? Can't this deadlock also in mainline?
> > > > 
> > > > It didn't with a NOPREEMPT kernel the one time I tried it, which seemed
> > > > mighty odd when I stared at the rt deadlock.  I'll give it another go, I
> > > > likely just munged q/d NOPREEMPT test.
> > > 
> > > Nope, no screw-up.  Maybe it can deadlock, but it refused to do so.
> > 
> > Lockdep should tell you if it could ...
> 
> I'll give that a shot.  I would expect the thing to gripe.. but then I
> expected the damn thing to deadlock properly with NOPREEMPT too, so.. :)
> 

But would it?

We have kworker blocked on the mutex where the owner did a flush_work(),
and waiting for kworker to finish because of a wait_for_completion(). I
don't see annotation here that will help lockdep catch such a thing.

-- Steve