linux-kernel - [PATCH 1/2] drm: zynqmp_dp: Fix a deadlock in zynqmp_dp_ignore_hpd

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Message-Id: <20250206194117.1496245-2-sean.anderson@linux.dev>
Date: Thu,  6 Feb 2025 14:41:18 -0500
From: Sean Anderson <sean.anderson@...ux.dev>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
	dri-devel@...ts.freedesktop.org (open list:DRM DRIVERS FOR XILINX)
Cc: Thomas Zimmermann <tzimmermann@...e.de>,
	linux-arm-kernel@...ts.infradead.org (moderated list:ARM/ZYNQ ARCHITECTURE),
	linux-kernel@...r.kernel.org (open list),
	David Airlie <airlied@...il.com>,
	Dan Carpenter <dan.carpenter@...aro.org>,
	Michal Simek <michal.simek@....com>,
	Maxime Ripard <mripard@...nel.org>,
	Simona Vetter <simona@...ll.ch>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Bart Van Assche <bvanassche@....org>,
	Sean Anderson <sean.anderson@...ux.dev>
Subject: [PATCH 1/2] drm: zynqmp_dp: Fix a deadlock in zynqmp_dp_ignore_hpd_set()

From: Bart Van Assche <bvanassche@....org>

Instead of attempting the same mutex twice, lock and unlock it.

This bug has been detected by the Clang thread-safety analyzer.

Cc: Sean Anderson <sean.anderson@...ux.dev>
Cc: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Fixes: 28edaacb821c ("drm: zynqmp_dp: Add debugfs interface for compliance testing")
Signed-off-by: Bart Van Assche <bvanassche@....org>
Reviewed-by: Sean Anderson <sean.anderson@...ux.dev>
Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
---

 drivers/gpu/drm/xlnx/zynqmp_dp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
index 979f6d3239ba..189a08cdc73c 100644
--- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
+++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
@@ -2295,7 +2295,7 @@ static int zynqmp_dp_ignore_hpd_set(void *data, u64 val)
 
 	mutex_lock(&dp->lock);
 	dp->ignore_hpd = val;
-	mutex_lock(&dp->lock);
+	mutex_unlock(&dp->lock);
 	return 0;
 }
 
-- 
2.35.1.1320.gc452695387.dirty