linux-kernel - [PATCH RFC 24/33] drm: zynqmp_dp: Fix a deadlock in zynqmp_dp_ignore_hpd

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Message-ID: <20250206175114.1974171-25-bvanassche@acm.org>
Date: Thu,  6 Feb 2025 09:51:05 -0800
From: Bart Van Assche <bvanassche@....org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Will Deacon <will@...nel.org>,
	Christoph Hellwig <hch@....de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Marco Elver <elver@...gle.com>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Kees Cook <kees@...nel.org>,
	Jann Horn <jannh@...gle.com>,
	linux-kernel@...r.kernel.org,
	Bart Van Assche <bvanassche@....org>,
	Sean Anderson <sean.anderson@...ux.dev>,
	Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Subject: [PATCH RFC 24/33] drm: zynqmp_dp: Fix a deadlock in zynqmp_dp_ignore_hpd_set()

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>
---
 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;
 }