[PATCH 2/2] drm/dp/mst: take lock around looking up the branch device on hpd irq

[Daniel Vetter]

On Mon, Jun 22, 2015 at 02:40:44PM +1000, Dave Airlie wrote:
> From: Dave Airlie <airlied at redhat.com>
> 
> If we are doing an MST transaction and we've gotten HPD and we
> lookup the device from the incoming msg, we should take the mgr
> lock around it, so that mst_primary and mstb->ports are valid.
> 
> Signed-off-by: Dave Airlie <airlied at redhat.com>

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 3c7e5cd..15a6d8e 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -1175,6 +1175,8 @@ static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device(struct drm_dp_mst_
>  	struct drm_dp_mst_port *port;
>  	int i;
>  	/* find the port by iterating down */
> +
> +	mutex_lock(&mgr->lock);
>  	mstb = mgr->mst_primary;
>  
>  	for (i = 0; i < lct - 1; i++) {
> @@ -1194,6 +1196,7 @@ static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device(struct drm_dp_mst_
>  		}
>  	}
>  	kref_get(&mstb->kref);
> +	mutex_unlock(&mgr->lock);
>  	return mstb;
>  }
>  
> -- 
> 2.4.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch