linux-kernel - [PATCH V3] amdgpu:optimization-- reduce no need mutex

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Date:   Mon, 20 Apr 2020 23:48:18 -0700
From:   Bernard Zhao <bernard@...o.com>
To:     Felix Kuehling <Felix.Kuehling@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc:     opensource.kernel@...o.com, Bernard Zhao <bernard@...o.com>
Subject: [PATCH V3] amdgpu:optimization-- reduce no need mutex_lock area

Maybe we could reduce the mutex_lock(&mem->lock)`s protected code area,
and no need to protect pr_debug.

Signed-off-by: Bernard Zhao <bernard@...o.com>

Changes since V1:
*commit message improve

Changes since V2:
*move comment along with the mutex_unlock

Link for V1:
*https://lore.kernel.org/patchwork/patch/1226588/
Link for V2:
*https://lore.kernel.org/patchwork/patch/1227907/
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
index 327317c54f7c..f03d9843d723 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
@@ -1285,21 +1285,21 @@ int amdgpu_amdkfd_gpuvm_free_memory_of_gpu(
 	struct bo_vm_reservation_context ctx;
 	struct ttm_validate_buffer *bo_list_entry;
 	int ret;
+	unsigned int mapped_to_gpu_memory;
 
 	mutex_lock(&mem->lock);
+	mapped_to_gpu_memory = mem->mapped_to_gpu_memory;
+	mutex_unlock(&mem->lock);
+	/* lock is not needed after this, since mem is unused and will
+	 * be freed anyway
+	 */
 
-	if (mem->mapped_to_gpu_memory > 0) {
+	if (mapped_to_gpu_memory > 0) {
 		pr_debug("BO VA 0x%llx size 0x%lx is still mapped.\n",
 				mem->va, bo_size);
-		mutex_unlock(&mem->lock);
 		return -EBUSY;
 	}
 
-	mutex_unlock(&mem->lock);
-	/* lock is not needed after this, since mem is unused and will
-	 * be freed anyway
-	 */
-
 	/* No more MMU notifiers */
 	amdgpu_mn_unregister(mem->bo);
 
-- 
2.26.2