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

[Christian König]

Am 16.02.2017 um 12:39 schrieb Nicolai Hähnle:
> From: Nicolai Hähnle <nicolai.haehnle at 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 at amd.com>
> ---
>   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 at amd.com>.

Regards,
Christian.

>   	*bo_ptr = bo;
>   
>   	trace_amdgpu_bo_create(bo);