linux-kernel - Re: [PATCH] drm/amd/display: Simplify same effect if/else blocks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <f15b10a8-11f6-6c1f-c94e-71796aad9155@amd.com>
Date:   Thu, 2 Mar 2023 11:37:30 -0500
From:   Harry Wentland <harry.wentland@....com>
To:     Deepak R Varma <drv@...lo.com>, Joe Perches <joe@...ches.com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Aurabindo Pillai <aurabindo.pillai@....com>
Cc:     Leo Li <sunpeng.li@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Saurabh Singh Sengar <ssengar@...rosoft.com>,
        Praveen Kumar <kumarpraveen@...ux.microsoft.com>
Subject: Re: [PATCH] drm/amd/display: Simplify same effect if/else blocks



On 3/1/23 15:21, Deepak R Varma wrote:
> On Mon, Jan 23, 2023 at 12:23:19AM +0530, Deepak R Varma wrote:
>> On Sun, Jan 15, 2023 at 12:52:10PM -0800, Joe Perches wrote:
>>> On Sun, 2023-01-15 at 15:30 +0530, Deepak R Varma wrote:
>>>> The if / else block code has same effect irrespective of the logical
>>>> evaluation.  Hence, simply the implementation by removing the unnecessary
>>>> conditional evaluation. While at it, also fix the long line checkpatch
>>>> complaint. Issue identified using cond_no_effect.cocci Coccinelle
>>>> semantic patch script.
>>>>
>>>> Signed-off-by: Deepak R Varma <drv@...lo.com>
>>>> ---
>>>> Please note: The proposed change is compile tested only. If there are any
>>>> inbuilt test cases that I should run for further verification, I will appreciate
>>>> guidance about it. Thank you.
>>>
>>> Preface: I do not know the code.
>>>
>>> Perhaps Rodrigo Siqueira made a copy/paste error submitting the code for
>>> commit 9114b55fabae ("drm/amd/display: Fix SubVP control flow in the MPO context")
>>> as the code prior to this change is identical.
>>>
>>> Perhaps one of the false uses should be true or dependent on the
>>> interdependent_update_lock state.
>>
>> Thank you Joe for the recommendation.
>>
>> Hi Rodrigo,
>> Can you review and comment on if and what is wrong with your commit?
> 
> Hello Rodrigo, Alex,
> Could you please suggest what would be the necessary fix for this typo error?
> 

It's not quite a "typo" error. When I look at this code in our internal repo I see
a couple missing lock calls here that differ between the two cases. I don't know why
this was never ported over and am surprised it doesn't lead to issues.

I would prefer we keep the code as-is for now until this gets sorted.

Harry

> Thank you,
> Deepak.
> 
>>
>> Thank you,
>> ./drv
>>
>>>
>>>> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
>>> []
>>>> @@ -3470,14 +3470,9 @@ static void commit_planes_for_stream(struct dc *dc,
>>>>  		/* Since phantom pipe programming is moved to post_unlock_program_front_end,
>>>>  		 * move the SubVP lock to after the phantom pipes have been setup
>>>>  		 */
>>>> -		if (should_lock_all_pipes && dc->hwss.interdependent_update_lock) {
>>>> -			if (dc->hwss.subvp_pipe_control_lock)
>>>> -				dc->hwss.subvp_pipe_control_lock(dc, context, false, should_lock_all_pipes, NULL, subvp_prev_use);
>>>> -		} else {
>>>> -			if (dc->hwss.subvp_pipe_control_lock)
>>>> -				dc->hwss.subvp_pipe_control_lock(dc, context, false, should_lock_all_pipes, NULL, subvp_prev_use);
>>>> -		}
>>>> -
>>>
>>> Perhaps something like:
>>>
>>> 		if (dc->hwss.subvp_pipe_control_lock)
>>> 			dc->hwss.subvp_pipe_control_lock(dc, context,
>>> 							 should_lock_all_pipes &&
>>> 							 dc->hwss.interdependent_update_lock,
>>> 							 should_lock_all_pipes, NULL, subvp_prev_use);
>>>
>>>> +		if (dc->hwss.subvp_pipe_control_lock)
>>>> +			dc->hwss.subvp_pipe_control_lock(dc, context, false, should_lock_all_pipes,
>>>> +							 NULL, subvp_prev_use);
>>>>  		return;
>>>>  	}
>>>>  
>>>
>>
>>
> 
>