Re: [PATCH v3 3/3] drm/amdgpu: simplify reservation handling during buffer creation

[zhoucm1 <david1.zhou@amd.com>]

On 2017年02月16日 20:08, Christian König wrote:
> Am 16.02.2017 um 12:39 schrieb Nicolai Hähnle:
>> From: Nicolai Hähnle <nicolai.haehnle@amd.com>
>>
>> By using ttm_bo_init_reserved instead of the manual initialization of
>> the reservation object, the reservation lock will be properly unlocked
>> and destroyed when the TTM BO initialization fails.
>>
>> Actual deadlocks caused by the missing unlock should have been fixed
>> by "drm/ttm: never add BO that failed to validate to the LRU list",
>> superseding the flawed fix in commit 38fc4856ad98 ("drm/amdgpu: fix
>> a potential deadlock in amdgpu_bo_create_restricted()").
>>
>> This change fixes remaining recursive locking errors that can be seen
>> with lock debugging enabled, and avoids the error of freeing a locked
>> mutex.
>>
>> As an additional minor bonus, buffers created with resv == NULL and
>> the AMDGPU_GEM_CREATE_VRAM_CLEARED flag are now only added to the
>> global LRU list after the fill commands have been issued.
>>
>> Fixes: 12a852219583 ("drm/amdgpu: improve 
>> AMDGPU_GEM_CREATE_VRAM_CLEARED handling (v2)")
>> Signed-off-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com> as well

>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 17 ++++-------------
>>   1 file changed, 4 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>> index c2e57f7..4d0536d 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>> @@ -395,19 +395,10 @@ int amdgpu_bo_create_restricted(struct 
>> amdgpu_device *adev,
>>       amdgpu_fill_placement_to_bo(bo, placement);
>>       /* Kernel allocation are uninterruptible */
>>   -    if (!resv) {
>> -        bool locked;
>> -
>> -        reservation_object_init(&bo->tbo.ttm_resv);
>> -        locked = ww_mutex_trylock(&bo->tbo.ttm_resv.lock);
>> -        WARN_ON(!locked);
>> -    }
>> -
>>       initial_bytes_moved = atomic64_read(&adev->num_bytes_moved);
>> -    r = ttm_bo_init(&adev->mman.bdev, &bo->tbo, size, type,
>> -            &bo->placement, page_align, !kernel, NULL,
>> -            acc_size, sg, resv ? resv : &bo->tbo.ttm_resv,
>> -            &amdgpu_ttm_bo_destroy);
>> +    r = ttm_bo_init_reserved(&adev->mman.bdev, &bo->tbo, size, type,
>> +                 &bo->placement, page_align, !kernel, NULL,
>> +                 acc_size, sg, resv, &amdgpu_ttm_bo_destroy);
>>       amdgpu_cs_report_moved_bytes(adev,
>>           atomic64_read(&adev->num_bytes_moved) - initial_bytes_moved);
>>   @@ -433,7 +424,7 @@ int amdgpu_bo_create_restricted(struct 
>> amdgpu_device *adev,
>>           fence_put(fence);
>>       }
>>       if (!resv)
>> -        ww_mutex_unlock(&bo->tbo.resv->lock);
>> +        ttm_bo_unreserve(&bo->tbo);
>
> You can just use amdgpu_bo_unreserve() here. With that fixed the whole 
> set is Reviewed-by: Christian König <christian.koenig@amd.com>.
>
> Regards,
> Christian.
>
>>       *bo_ptr = bo;
>>         trace_amdgpu_bo_create(bo);
>
>
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