Re: [PATCH] drm/nouveau: Drop mutex_lock_nested for atomic

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 02-08-2020 om 20:18 schreef Daniel Vetter:
> Purely conjecture, but I think the original locking inversion with the
> legacy page flip code between flipping and ttm's bo move function
> shoudn't exist anymore with atomic: With atomic the bo pinning and
> actual modeset commit is completely separated in the code patsh.
>
> This annotation was originally added in
>
> commit 060810d7abaabcab282e062c595871d661561400
> Author: Ben Skeggs <bskeggs@redhat.com>
> Date:   Mon Jul 8 14:15:51 2013 +1000
>
>     drm/nouveau: fix locking issues in page flipping paths
>
> due to
>
> commit b580c9e2b7ba5030a795aa2fb73b796523d65a78
> Author: Maarten Lankhorst <m.b.lankhorst@gmail.com>
> Date:   Thu Jun 27 13:48:18 2013 +0200
>
>     drm/nouveau: make flipping lockdep safe
>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> Cc: Maarten Lankhorst <m.b.lankhorst@gmail.com>
> Cc: Ben Skeggs <bskeggs@redhat.com>
> Cc: Dave Airlie <airlied@gmail.com>
> Cc: nouveau@lists.freedesktop.org
> ---
> I might be totally wrong, so this definitely needs testing :-)
>
> Cheers, Daniel
> ---
>  drivers/gpu/drm/nouveau/nouveau_bo.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
> index 7806278dce57..a7b2a9bb0ffe 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_bo.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
> @@ -776,7 +776,11 @@ nouveau_bo_move_m2mf(struct ttm_buffer_object *bo, int evict, bool intr,
>  			return ret;
>  	}
>  
> -	mutex_lock_nested(&cli->mutex, SINGLE_DEPTH_NESTING);
> +	if (drm_drv_uses_atomic_modeset(drm->dev))
> +		mutex_lock(&cli->mutex);
> +	else
> +		mutex_lock_nested(&cli->mutex, SINGLE_DEPTH_NESTING);
> +
>  	ret = nouveau_fence_sync(nouveau_bo(bo), chan, true, intr);
>  	if (ret == 0) {
>  		ret = drm->ttm.move(chan, bo, &bo->mem, new_reg);

Well if you're certain it works now. :)

Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

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