Broken locking in ttm_bo_swapout

[Maarten Maathuis]

On Thu, Jan 20, 2011 at 7:53 PM, Matthew Bullock
<matthew.bullock at tadpole.com> wrote:
> I have a fairly simple opengl application running on nouveau. It effectively
> just plots a couple of very large images that change regularly.
>
> I've been getting an easily repeatable failure, hitting the
> BUG_ON(in_interrupt) in vfree() that is called during ttm_shrink_work().
> Obviously vfree() is being called with a lock held...
>
> Looking at the locking up through the stack trace, there's an obvious
> mistake:
>
> There should be a:
> spin_lock(&glob->lru_lock);
> before the continue in ttm_bo_swapout() in drivers/gpu/drm/ttm/ttm_bo.c
>
> --- ttm_bo.c~   2011-01-05 00:50:19.000000000 +0000
> +++ ttm_bo.c    2011-01-20 18:11:57.262813765 +0000
> @@ -1761,6 +1761,7 @@ static int ttm_bo_swapout(struct ttm_mem
>                        spin_unlock(&glob->lru_lock);
>                        (void) ttm_bo_cleanup_refs(bo, false, false, false);
>                        kref_put(&bo->list_kref, ttm_bo_release_list);
> +                       spin_lock(&glob->lru_lock);
>                        continue;
>                }
>
> That fixes the problem for me.
>
> Matthew
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>

This seems (very) plausible, maybe someone who commits drm patches
frequently will see this message now.

It would be a shame to forget about this e-mail.

Maarten.

-- 
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