linux-kernel - [PATCH v1 7/8] MT9M114: Fix deadlock in get_frame_interval/set_frame

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Message-Id: <20250226153929.274562-8-mathis.foerst@mt.com>
Date: Wed, 26 Feb 2025 16:39:28 +0100
From: Mathis Foerst <mathis.foerst@...com>
To: linux-kernel@...r.kernel.org
Cc: Mathis Foerst <mathis.foerst@...com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	linux-media@...r.kernel.org,
	devicetree@...r.kernel.org,
	manuel.traut@...com
Subject: [PATCH v1 7/8] MT9M114: Fix deadlock in get_frame_interval/set_frame_interval

Getting / Setting the frame interval using the V4L2 subdev pad ops
get_frame_interval/set_frame_interval causes a deadlock, as the subdev
state is locked in the [1] but also in the driver itself.

In [2] it's described that the caller is responsible to acquire and
release the lock in this case. Therefore, acquiring the lock in the
driver is wrong.

Remove the lock acquisitions/releases from mt9m114_ifp_get_frame_interval()
and mt9m114_ifp_set_frame_interval().

[1] drivers/media/v4l2-core/v4l2-subdev.c - line 1129
[2] Documentation/driver-api/media/v4l2-subdev.rst

Signed-off-by: Mathis Foerst <mathis.foerst@...com>
---
 drivers/media/i2c/mt9m114.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/drivers/media/i2c/mt9m114.c b/drivers/media/i2c/mt9m114.c
index 5c0a8a940fd2..f96f6c010e1b 100644
--- a/drivers/media/i2c/mt9m114.c
+++ b/drivers/media/i2c/mt9m114.c
@@ -1644,13 +1644,9 @@ static int mt9m114_ifp_get_frame_interval(struct v4l2_subdev *sd,
 	if (interval->which != V4L2_SUBDEV_FORMAT_ACTIVE)
 		return -EINVAL;
 
-	mutex_lock(sensor->ifp.hdl.lock);
-
 	ival->numerator = 1;
 	ival->denominator = sensor->ifp.frame_rate;
 
-	mutex_unlock(sensor->ifp.hdl.lock);
-
 	return 0;
 }
 
@@ -1669,8 +1665,6 @@ static int mt9m114_ifp_set_frame_interval(struct v4l2_subdev *sd,
 	if (interval->which != V4L2_SUBDEV_FORMAT_ACTIVE)
 		return -EINVAL;
 
-	mutex_lock(sensor->ifp.hdl.lock);
-
 	if (ival->numerator != 0 && ival->denominator != 0)
 		sensor->ifp.frame_rate = min_t(unsigned int,
 					       ival->denominator / ival->numerator,
@@ -1684,8 +1678,6 @@ static int mt9m114_ifp_set_frame_interval(struct v4l2_subdev *sd,
 	if (sensor->streaming)
 		ret = mt9m114_set_frame_rate(sensor);
 
-	mutex_unlock(sensor->ifp.hdl.lock);
-
 	return ret;
 }
 
-- 
2.34.1