linux-kernel - Possible deadlock in jfs

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Date:	Sat, 23 May 2009 17:19:12 +0200
From:	Jan Kucera <kucera.jan.cz@...il.com>
To:	jfs-discussion@...ts.sourceforge.net
Cc:	shaggy@...tin.ibm.com, linux-kernel@...r.kernel.org
Subject: Possible deadlock in jfs_imap.c?

Hi,

for my master thesis, I've designed static checker for finding deadlocks in C.
My tool found some possible deadlock in file fs/jfs/jfs_imap.c
between JFS_IP(ipimap)->commit_mutex and  imap->im_aglock[agno].

Reason of this problem is probably missed unlocking of
JFS_IP(ipimap)->commit_mutex in branch starting at line 2564 which
leaves JFS_IP(ipimap)->commit_mutex locked:

    in function diNewIAG(..)
        locking mutex_lock(&JFS_IP(ipimap)->commit_mutex) at line 2540
        condition at line 2543 is false
        condition at line 2564 is true
        goto out: at 2579
        IAGFREE_UNLOCK(imap); at line 2654
    return from diNewIAG(..) at line 2656

Version of kernel is 2.6.28 (maybe this code is in newer versions too).
Could someone confirm, that this is a real bug? Thank you for your time.
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