linux-kernel - Re: [rfc patch] fs,reiserfs: unlock superblock before callling reiserfs_quota_on

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Message-ID: <1344967797.4282.8.camel@marge.simpson.net>
Date:	Tue, 14 Aug 2012 20:09:57 +0200
From:	Mike Galbraith <efault@....de>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"linux-rt-users@...r.kernel.org" <linux-rt-users@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [rfc patch] fs,reiserfs: unlock superblock before callling
 reiserfs_quota_on_mount()

On Tue, 2012-08-14 at 13:44 -0400, Steven Rostedt wrote: 
> 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.

Hm.. <zzzt>.  Ok, you saved me a long kernel build, but cost me a fuse.

-Mike

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