* Possible deadlock in jfs_imap.c?
@ 2009-05-23 15:19 Jan Kucera
2009-05-24 1:26 ` Dave Kleikamp
0 siblings, 1 reply; 2+ messages in thread
From: Jan Kucera @ 2009-05-23 15:19 UTC (permalink / raw
To: jfs-discussion; +Cc: shaggy, linux-kernel
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.
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Possible deadlock in jfs_imap.c?
2009-05-23 15:19 Possible deadlock in jfs_imap.c? Jan Kucera
@ 2009-05-24 1:26 ` Dave Kleikamp
0 siblings, 0 replies; 2+ messages in thread
From: Dave Kleikamp @ 2009-05-24 1:26 UTC (permalink / raw
To: Jan Kucera; +Cc: JFS Discussion, linux-kernel
On Sat, 2009-05-23 at 17:19 +0200, Jan Kucera wrote:
> 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.
Yes, it looks like a real bug. As the comment states, it's an unlikely
error path. This would explain how it went undetected this long. Should
be fixed anyway.
Thanks,
Shaggy
--
David Kleikamp
IBM Linux Technology Center
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