linux-kernel - Re: [PATCH v2 04/10] drm/amd/display: use eld_mutex to protect access to connector->eld

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Message-ID: <fc8e80dd-bcea-4515-b446-158649719569@amd.com>
Date: Mon, 16 Dec 2024 09:53:45 -0500
From: Harry Wentland <harry.wentland@....com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Leo Li <sunpeng.li@....com>, Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
 Alex Deucher <alexander.deucher@....com>,
 Christian König <christian.koenig@....com>,
 Xinhui Pan <Xinhui.Pan@....com>, Andrzej Hajda <andrzej.hajda@...el.com>,
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Phong LE <ple@...libre.com>, Inki Dae <inki.dae@...sung.com>,
 Seung-Woo Kim <sw0312.kim@...sung.com>,
 Kyungmin Park <kyungmin.park@...sung.com>,
 Krzysztof Kozlowski <krzk@...nel.org>, Alim Akhtar
 <alim.akhtar@...sung.com>, Jani Nikula <jani.nikula@...ux.intel.com>,
 Rodrigo Vivi <rodrigo.vivi@...el.com>,
 Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
 Tvrtko Ursulin <tursulin@...ulin.net>, Rob Clark <robdclark@...il.com>,
 Abhinav Kumar <quic_abhinavk@...cinc.com>, Sean Paul <sean@...rly.run>,
 Marijn Suijten <marijn.suijten@...ainline.org>,
 Alain Volmat <alain.volmat@...s.st.com>,
 Raphael Gallais-Pou <rgallaispou@...il.com>,
 Dave Stevenson <dave.stevenson@...pberrypi.com>,
 Maíra Canal <mcanal@...lia.com>,
 Raspberry Pi Kernel Maintenance <kernel-list@...pberrypi.com>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 amd-gfx@...ts.freedesktop.org, linux-arm-kernel@...ts.infradead.org,
 linux-samsung-soc@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
 intel-xe@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
 freedreno@...ts.freedesktop.org
Subject: Re: [PATCH v2 04/10] drm/amd/display: use eld_mutex to protect access
 to connector->eld



On 2024-12-10 16:20, Dmitry Baryshkov wrote:
> On Fri, Dec 06, 2024 at 11:43:07AM +0200, Dmitry Baryshkov wrote:
>> Reading access to connector->eld can happen at the same time the
>> drm_edid_to_eld() updates the data. Take the newly added eld_mutex in
>> order to protect connector->eld from concurrent access.
>>
>> Reviewed-by: Maxime Ripard <mripard@...nel.org>
>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>> ---
>>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 ++
>>  1 file changed, 2 insertions(+)
> 
> Harry, Leo, Rodrigo, Alex, Christian, Xinhui, any response to this one
> and to the radeon patches? I'd like to be able to pick the series for
> drm-misc and these two are not reviewed by you.
> 
>>
>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> index 19a58630e774029767bf2a27eb4ddf17e3c21129..04c68c320252b5ce9647f0606fb86fe57f347639 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> @@ -1037,8 +1037,10 @@ static int amdgpu_dm_audio_component_get_eld(struct device *kdev, int port,
>>  			continue;
>>  
>>  		*enabled = true;
>> +		mutex_lock(&connector->eld_mutex);
>>  		ret = drm_eld_size(connector->eld);
>>  		memcpy(buf, connector->eld, min(max_bytes, ret));
>> +		mutex_unlock(&connector->eld_mutex);

All of this is wrapped by the adev->dm.audio_lock mutex. It might
be safer to modify the audio_lock mutex so it only guards the
aconnector->audio_inst access.

But I don't see any way these mutexes would otherwise interact,
so this change should be good as-is.

Reviewed-by: Harry Wentland <harry.wentland@....com>

Harry

>>  
>>  		break;
>>  	}
>>
>> -- 
>> 2.39.5
>>
>