linux-kernel - Re: xfs_io "BUG: lock held when returning to user space!" on suspend

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Message-Id: <1207231620.8514.829.camel@twins>
Date:	Thu, 03 Apr 2008 16:07:00 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	David Chinner <dgc@....com>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>, xfs-masters@....sgi.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: xfs_io "BUG: lock held when returning to user space!" on
	suspend

On Thu, 2008-04-03 at 15:53 +0200, Peter Zijlstra wrote:
> On Thu, 2008-04-03 at 07:57 +1000, David Chinner wrote:
> > On Wed, Apr 02, 2008 at 11:58:54AM -0700, Jeremy Fitzhardinge wrote:
> > > I'm getting this:
> > > 
> > > ================================================
> > > [ BUG: lock held when returning to user space! ]
> > > ------------------------------------------------
> > > xfs_io/18796 is leaving the kernel with locks still held!
> > > 1 lock held by xfs_io/18796:
> > > #0:  (&type->s_umount_key#19){----}, at: [<c048c9ac>] get_super+0x42/0x87
> > > 
> > > when I suspend, possibly during an xfs-freeze.  There don't seem to be any 
> > > ill-effects.
> > 
> > Yup, both the sb->s_umount and bdev->bd_mount_sem seaphores are held
> > across freeze_bdev()/thaw_bdev(), and they are issued via separate
> > ioctls generally from separate processes. Not great design, but not
> > a bug....
> 
> Actually... we do consider that bugs.

http://lkml.org/lkml/2007/10/27/135

Where Linus says:

 Definitely not a sane thing to do. It should use ref-counting and/or a 
single bit to say "busy". 

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