linux-kernel - Re: [PATCH v2 1/2] drm: zynqmp_dp: Fix a deadlock in zynqmp_dp_ignore_hpd

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Message-ID: <20250207163317.GA5869@pendragon.ideasonboard.com>
Date: Fri, 7 Feb 2025 18:33:17 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Sean Anderson <sean.anderson@...ux.dev>
Cc: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
	"open list:DRM DRIVERS FOR XILINX" <dri-devel@...ts.freedesktop.org>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Michal Simek <michal.simek@....com>,
	Maxime Ripard <mripard@...nel.org>,
	open list <linux-kernel@...r.kernel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Bart Van Assche <bvanassche@....org>,
	Dan Carpenter <dan.carpenter@...aro.org>,
	"moderated list:ARM/ZYNQ ARCHITECTURE" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2 1/2] drm: zynqmp_dp: Fix a deadlock in
 zynqmp_dp_ignore_hpd_set()

Hi Sean, Bart,

Thank you for the patch.

On Fri, Feb 07, 2025 at 11:25:27AM -0500, Sean Anderson wrote:
> 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>

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> ---
> 
> (no changes since v1)
> 
>  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;
>  }
>  

-- 
Regards,

Laurent Pinchart