linux-kernel - Re: [PATCH v1] drm/dp/mst: fix missing modeset unlock for MST port detect

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Date:   Fri, 22 Sep 2023 15:02:23 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     Ramya SR <quic_rsr@...cinc.com>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, Wayne Lin <Wayne.Lin@....com>,
        Jani Nikula <jani.nikula@...el.com>,
        Imre Deak <imre.deak@...el.com>,
        Alex Deucher <alexander.deucher@....com>,
        Jeff Layton <jlayton@...nel.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] drm/dp/mst: fix missing modeset unlock for MST port
 detect


Oh! wow thank you for catching this:

Reviewed-by: Lyude Paul <lyude@...hat.com>

I will go and push this to drm-misc-next in just a moment

On Fri, 2023-09-15 at 10:24 +0530, Ramya SR wrote:
> Modeset mutex unlock is missing in drm_dp_mst_detect_port function.
> This will lead to deadlock if calling the function multiple times in
> an atomic operation, for example, getting imultiple MST ports status
> for a DP MST bonding scenario.
> 
> Signed-off-by: Ramya SR <quic_rsr@...cinc.com>
> ---
>  drivers/gpu/drm/display/drm_dp_mst_topology.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> index ed96cfc..d6512c4 100644
> --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> @@ -4154,7 +4154,7 @@ drm_dp_mst_detect_port(struct drm_connector *connector,
>  
>  	ret = drm_modeset_lock(&mgr->base.lock, ctx);
>  	if (ret)
> -		goto out;
> +		goto fail;
>  
>  	ret = connector_status_disconnected;
>  
> @@ -4181,6 +4181,8 @@ drm_dp_mst_detect_port(struct drm_connector *connector,
>  		break;
>  	}
>  out:
> +	drm_modeset_unlock(&mgr->base.lock);
> +fail:
>  	drm_dp_mst_topology_put_port(port);
>  	return ret;
>  }

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat