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Re: BUG: sleeping function called from invalid context at kernel/rwsem.c

To: Alexander Beregalov <a.beregalov@xxxxxxxxx>
Subject: Re: BUG: sleeping function called from invalid context at kernel/rwsem.c:131 XFS? (was: Re: linux-next: Tree for October 17)
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 22 Oct 2008 18:58:38 +1100
Cc: lachlan@xxxxxxx, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Arjan van de Ven <arjan@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, linux-next@xxxxxxxxxxxxxxx, LKML <linux-kernel@xxxxxxxxxxxxxxx>
In-reply-to: <a4423d670810210442y51b62fc2naf6cb649e6b26942@xxxxxxxxxxxxxx>
Mail-followup-to: Alexander Beregalov <a.beregalov@xxxxxxxxx>, lachlan@xxxxxxx, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Arjan van de Ven <arjan@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, linux-next@xxxxxxxxxxxxxxx, LKML <linux-kernel@xxxxxxxxxxxxxxx>
References: <a4423d670810170954h7ca130aaw8895380a4c6b125@xxxxxxxxxxxxxx> <20081017165738.GA20818@xxxxxxxxxxxxx> <a4423d670810171013g5bc19c1cm3f7d9c014ee70349@xxxxxxxxxxxxxx> <20081017203710.GA27187@xxxxxxxxxxxxx> <20081017135510.7127c4e7@xxxxxxxxxxxxx> <a4423d670810200758m3cea3841h40988afc8eaf81@xxxxxxxxxxxxxx> <20081020163327.GA15651@xxxxxxxxxxxxx> <a4423d670810201013w6448cb38w402771799cefb5f5@xxxxxxxxxxxxxx> <20081020223549.GA21152@disturbed> <a4423d670810210442y51b62fc2naf6cb649e6b26942@xxxxxxxxxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Tue, Oct 21, 2008 at 03:42:16PM +0400, Alexander Beregalov wrote:
> 2008/10/21 Dave Chinner <david@xxxxxxxxxxxxx>:
> > On Mon, Oct 20, 2008 at 09:13:05PM +0400, Alexander Beregalov wrote:
> >> 2008/10/20 Christoph Hellwig <hch@xxxxxxxxxxxxx>:
> >> > On Mon, Oct 20, 2008 at 06:58:09PM +0400, Alexander Beregalov wrote:
> >> >> Hi Christoph
> >> >>
> >> >> I have the same result with next-1020 and today's xfs-2.6.git/master
> >> >> (
> >> >> commit bfd2bd10da76378dc4afd87d7d204a1d3d70b347
> >> >> Author: David Chinner <david@xxxxxxxxxxxxx>
> >> >> Date:   Fri Oct 17 15:36:23 2008 +1000
> >> >>     Inode: Allow external list initialisation
> >> >> )
> >> Ha, that kernel (xfs/master) has made my system dead locked.
> >> SysRQ-d:
> >> Show all locks held in the system
> >> 1 lock held by pdflush
> >> (&type->s_umount_key#18{----}, at writeback_inodes
> >> 1 lock held by login
> >> (&(&ip->i_iolock)->mr_lock){----} at xfs_ilock
> >> and so on ( many locks at xfs_ilock)
> >
> > Curious. Can you post the full stack traces?
> I can not reproduce it, yet.
> 
> Bisected to:
> dd509097cb0b76d3836385f80d6b2d6fd3b97757 is first bad commit
> commit dd509097cb0b76d3836385f80d6b2d6fd3b97757
> Author: Lachlan McIlroy <lachlan@xxxxxxx>
> Date:   Mon Sep 29 14:56:40 2008 +1000
> 
>     [XFS] Unlock inode before calling xfs_idestroy()
> 
>     Lock debugging reported the ilock was being destroyed without being
>     unlocked. We don't need to lock the inode until we are going to insert it
>     into the radix tree.

Ah, OK, I see the problem, though I don't understand why I'm not
seeing the might_sleep() triggering all the time given that I always
build with:

$ grep SLEEP .config
CONFIG_DEBUG_SPINLOCK_SLEEP=y

Basically the above commit moved xfs_ilock() inside
radix_tree_preload()/radix_tree_preload_end(), which means we are
taking a rwsem() while we have an elevated preempt count. I'll
get a patch out to fix it.

The question is why isn't this triggering for me during QA runs?

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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