linux-kernel - Re: [PATCH 0/4] kill-the-bkl/reiserfs: fix some lock dependency inversions

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Date:	Mon, 14 Sep 2009 23:50:13 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Alexander Beregalov <a.beregalov@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Reiserfs <reiserfs-devel@...r.kernel.org>
Subject: Re: [PATCH 0/4] kill-the-bkl/reiserfs: fix some lock dependency
	inversions

On Tue, Sep 15, 2009 at 01:33:42AM +0400, Alexander Beregalov wrote:
> > Hi Alexander,
> >
> > It should be fixed now, still in the following tree:
> 
> Hi!
> Another one, similar:
> It is v2.6.31-3123-g99bc470 plus your 805031859(kill-the-bkl/reiserfs:
> panic in case of lock imbalance), UP.
> 
> =======================================================
> [ INFO: possible circular locking dependency detected ]
> 2.6.31-03149-gdcc030a #1
> -------------------------------------------------------
> udevadm/716 is trying to acquire lock:
>  (&mm->mmap_sem){++++++}, at: [<c107249a>] might_fault+0x4a/0xa0



I hate this mm->mmap_sem....



> 
> but task is already holding lock:
>  (sysfs_mutex){+.+.+.}, at: [<c10cb9aa>] sysfs_readdir+0x5a/0x200
> 
> which lock already depends on the new lock.



This is really weird. This is two externals locks from reiserfs.
I guess I created this dependency somewhere, but how...

Anyway, someone reported a similar bug with this tree some months ago,
I've even met it once but could never be able to reproduce it anymore.

I'll try to find out. Thanks!

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