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 09:41:34 +0000
From:   Ramya SR <rsr@....qualcomm.com>
To:     "Ramya SR (QUIC)" <quic_rsr@...cinc.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, Lyude Paul <lyude@...hat.com>,
        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" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v1] drm/dp/mst: fix missing modeset unlock for MST port
 detect

Gentle Reminder. Please review the commit.

-----Original Message-----
From: Ramya SR (QUIC) <quic_rsr@...cinc.com> 
Sent: Friday, September 15, 2023 10:25 AM
To: David Airlie <airlied@...il.com>; Daniel Vetter <daniel@...ll.ch>; Lyude Paul <lyude@...hat.com>; 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
Cc: Ramya SR (QUIC) <quic_rsr@...cinc.com>
Subject: [PATCH v1] drm/dp/mst: fix missing modeset unlock for MST port detect

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;
 }
--
2.7.4