linux-kernel - Re: 2.6.24-rc8: possible circular locking dependency detected

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Mon, 21 Jan 2008 13:55:10 +1100
From:	David Chinner <dgc@....com>
To:	Christian Kujau <lists@...dbynature.de>
Cc:	xfs@....sgi.com, LKML <linux-kernel@...r.kernel.org>,
	peterz@...radead.org, mingo@...hat.com
Subject: Re: 2.6.24-rc8: possible circular locking dependency detected

On Fri, Jan 18, 2008 at 10:45:17PM +0100, Christian Kujau wrote:
> Hi,
> 
> just FYI, upgrading to -rc8 gave the following messages in kern.log in
> the morning hours, when the backups were run:
> 
> =======================================================
> [ INFO: possible circular locking dependency detected ]
> 2.6.24-rc8 #2
> -------------------------------------------------------
> rsync/23295 is trying to acquire lock:
>  (iprune_mutex){--..}, at: [<c017a552>] shrink_icache_memory+0x72/0x220
> 
> but task is already holding lock:
>  (&(&ip->i_iolock)->mr_lock){----}, at: [<c0275056>] xfs_ilock+0x96/0xb0
> 
> which lock already depends on the new lock.

memory reclaim can occur when an inode lock is held,
causing i_iolock -> iprune_mutex to occur. This is quite
common.

During reclaim, while holding iprune_mutex, we lock a
different inode to complete the cleaning up of it,
resulting in iprune_mutex -> i_iolock.

At this point, lockdep gets upset and blats out a warning.

But, there's no problem here as it is always safe for us
to take the i_iolock in inode reclaim because it can never
be the same as the i_iolock that we've taken prior to memory
reclaim being entered. Therefore false positive.

Lockdep folk - we really need an annotation to prevent this false
positive from being reported because we are getting reports at
least once a week....

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/