linux-kernel - Re: [PATCH AUTOSEL 6.0 38/44] drm/amdgpu: Unlock bo_list

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Message-ID: <0916abd9-265d-e4ed-819b-9dfa05e8d746@amd.com>
Date:   Mon, 21 Nov 2022 12:07:40 +0100
From:   Christian König <christian.koenig@....com>
To:     Michel Dänzer <michel.daenzer@...lbox.org>,
        Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Cc:     Philip Yang <Philip.Yang@....com>, Xinhui.Pan@....com,
        amd-gfx@...ts.freedesktop.org, luben.tuikov@....com,
        dri-devel@...ts.freedesktop.org, daniel@...ll.ch,
        Alex Deucher <alexander.deucher@....com>, airlied@...il.com
Subject: Re: [PATCH AUTOSEL 6.0 38/44] drm/amdgpu: Unlock bo_list_mutex after
 error handling

Am 21.11.22 um 10:57 schrieb Michel Dänzer:
> On 11/19/22 03:11, Sasha Levin wrote:
>> From: Philip Yang <Philip.Yang@....com>
>>
>> [ Upstream commit 64f65135c41a75f933d3bca236417ad8e9eb75de ]
>>
>> Get below kernel WARNING backtrace when pressing ctrl-C to kill kfdtest
>> application.
>>
>> If amdgpu_cs_parser_bos returns error after taking bo_list_mutex, as
>> caller amdgpu_cs_ioctl will not unlock bo_list_mutex, this generates the
>> kernel WARNING.
>>
>> Add unlock bo_list_mutex after amdgpu_cs_parser_bos error handling to
>> cleanup bo_list userptr bo.
>>
>>   WARNING: kfdtest/2930 still has locks held!
>>   1 lock held by kfdtest/2930:
>>    (&list->bo_list_mutex){+.+.}-{3:3}, at: amdgpu_cs_ioctl+0xce5/0x1f10 [amdgpu]
>>    stack backtrace:
>>     dump_stack_lvl+0x44/0x57
>>     get_signal+0x79f/0xd00
>>     arch_do_signal_or_restart+0x36/0x7b0
>>     exit_to_user_mode_prepare+0xfd/0x1b0
>>     syscall_exit_to_user_mode+0x19/0x40
>>     do_syscall_64+0x40/0x80
>>
>> Signed-off-by: Philip Yang <Philip.Yang@....com>
>> Reviewed-by: Christian König <christian.koenig@....com>
>> Signed-off-by: Alex Deucher <alexander.deucher@....com>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>> index b7bae833c804..9d59f83c8faa 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>> @@ -655,6 +655,7 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser *p,
>>   		}
>>   		mutex_unlock(&p->bo_list->bo_list_mutex);
>>   	}
>> +	mutex_unlock(&p->bo_list->bo_list_mutex);
>>   	return r;
>>   }
>>   
> Looks doubtful that this is a correct backport — there's an identical mutex_unlock call just above.


Oh, yes good point. This patch doesn't needs to be backported at all 
because it just fixes a problem introduced in the same cycle:

commit 4953b6b22ab9d7f64706631a027b1ed1130ce4c8
Author: Christian König <christian.koenig@....com>
Date:   Tue Sep 13 09:52:13 2022 +0200

     drm/amdgpu: cleanup error handling in amdgpu_cs_parser_bos

     Return early on success and so remove all those "if (r)" in the error
     path.

     Signed-off-by: Christian König <christian.koenig@....com>
     Reviewed-by: Alex Deucher <alexander.deucher@....com>
     Signed-off-by: Alex Deucher <alexander.deucher@....com>

Regards,
Christian.