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

[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);
 	*bo_ptr = bo;
 
 	trace_amdgpu_bo_create(bo);
-- 
2.9.3