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

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Date:	Fri, 4 Apr 2008 11:50:06 +1000
From:	David Chinner <dgc@....com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	David Chinner <dgc@....com>, 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, Apr 03, 2008 at 03:53:14PM +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.

Ok, you're welcome to fix it then. It's way below my care factor
right now....

FWIW, I did suggest that this needed fixing before FIFREEZE/FITHAW
are introduced, but that hasn't happened yet.

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group
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