linux-kernel - Re: BUG: sleeping function called from invalid context at kernel/rwsem.c:131 XFS? (was: Re: linux-next: Tree for October 17)

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Date:	Thu, 23 Oct 2008 08:10:28 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Alexander Beregalov <a.beregalov@...il.com>, lachlan@....com,
	Arjan van de Ven <arjan@...radead.org>, xfs@....sgi.com,
	linux-next@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: BUG: sleeping function called from invalid context at
	kernel/rwsem.c:131 XFS? (was: Re: linux-next: Tree for October 17)

On Wed, Oct 22, 2008 at 06:13:51AM -0400, Christoph Hellwig wrote:
> On Wed, Oct 22, 2008 at 07:25:50PM +1100, Dave Chinner wrote:
> > > 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.
> 
> This really needs a warning.  Then again I don't really understand this
> as the point of radix_tree_preload was that we can do the actual
> radix-tree under a lock, or not?

Right - the preload allows us to do GFP_KERNEL allocations for radix
tree nodes and use a spinlock for inserts into the tree. We could
drop the preload stuff if we initialised the radix tree to use
GFP_ATOMIC allocations for radix tree nodes, but that is more likely
to lead to insert failures under low memory conditions compared to
the preload method.

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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