On Tue, 2009-10-20 at 20:48 +0200, Krzysztof Helt wrote:
> From: Krzysztof Helt <[email protected]>
>
> Release rdwrlock semaphore during memory allocation.
> This fixes the locked already reported here:
>
> http://www.mail-archive.com/[email protected]/msg01389.html
>
> The problem here is that memory allocation is done with rdwrlock
> semaphore taken and the VM can get into the jfs layer taking the
> rdwrlock again.
>
> Also, the patch fixes the lockdep below. This problem is created because
> the rdwrlock semaphore acquires the commit_mutex and it is called with
> interrupts enabled. The interrupt may hit with the commit_mutex taken
> and take the rdwrlock (again) inside the interrupt context.
The rdwrlock should never be taken in interrupt context.
> =========================================================
> [ INFO: possible irq lock inversion dependency detected ]
> 2.6.32-rc3 #99
> ---------------------------------------------------------
> kswapd0/180 just changed the state of lock:
> (&jfs_ip->rdwrlock#2){++++-.}, at: [<c02e2207>] jfs_get_block+0x47/0x280
> but this lock took another, RECLAIM_FS-unsafe lock in the past:
> (&jfs_ip->commit_mutex){+.+.+.}
>
> and interrupts could create inverse lock ordering between them.
>
>
> other info that might help us debug this:
> no locks held by kswapd0/180.
>
> the shortest dependencies between 2nd lock and 1st lock:
> -> (&jfs_ip->commit_mutex){+.+.+.} ops: 7937 {
> HARDIRQ-ON-W at:
<snip>
> ---
>
> I am not sure if this is the right fix to the problem. The heavy use of
> the jfs volume can lock up a machine (e.g. hit me in Ubuntu 9.04).
I don't think we can just drop the mutex, since it protects the inode's
xtree from being modified while another thread is either reading or
writing it.
I proposed another fix here:
http://bugzilla.kernel.org/show_bug.cgi?id=13613
It seems I haven't followed up and submitted it to the vfs maintainer.
Could you please give that patch a try and see if it fixes the problem
for you?
Thanks,
Shaggy
> diff --git a/fs/jfs/inode.c b/fs/jfs/inode.c
> index b2ae190..de18324 100644
> --- a/fs/jfs/inode.c
> +++ b/fs/jfs/inode.c
> @@ -244,9 +244,22 @@ int jfs_get_block(struct inode *ip, sector_t lblock,
> #ifdef _JFS_4K
> if ((rc = extHint(ip, lblock64 << ip->i_sb->s_blocksize_bits, &xad)))
> goto unlock;
> +
> + /* release lock to avoid lockdep with jfs_ip->commit_mutex */
> + if (create)
> + IWRITE_UNLOCK(ip);
> + else
> + IREAD_UNLOCK(ip);
> +
> rc = extAlloc(ip, xlen, lblock64, &xad, false);
> +
> if (rc)
> - goto unlock;
> + return rc;
> +
> + if (create)
> + IWRITE_LOCK(ip, RDWRLOCK_NORMAL);
> + else
> + IREAD_LOCK(ip, RDWRLOCK_NORMAL);
>
> set_buffer_new(bh_result);
> map_bh(bh_result, ip->i_sb, addressXAD(&xad));
--
David Kleikamp
IBM Linux Technology Center
------------------------------------------------------------------------------
Come build with us! The BlackBerry(R) Developer Conference in SF, CA
is the only developer event you need to attend this year. Jumpstart your
developing skills, take BlackBerry mobile applications to market and stay
ahead of the curve. Join us from November 9 - 12, 2009. Register now!
http://p.sf.net/sfu/devconference
_______________________________________________
Jfs-discussion mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/jfs-discussion
