Re: Broken locking in ttm_bo_swapout

[Thomas Hellstrom <thomas@shipmail.org>]

On 01/20/2011 07:53 PM, Matthew Bullock 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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Indeed this fix looks correct. Sorry for taking so long to respond.
Could you spin a patch against Dave's drm-fixes tree or do you want me 
to do that?

Thanks,
Thomas