[PATCH] drm/amdgpu: Fix the dead lock issue.

[Emily Deng]

It will ramdomly have the dead lock issue when test TDR:
1. amdgpu_device_handle_vram_lost gets the lock shadow_list_lock
2. amdgpu_bo_create locked the bo's resv lock
3. amdgpu_bo_create_shadow is waiting for the shadow_list_lock
4. amdgpu_device_recover_vram_from_shadow is waiting for the bo's resv
lock.

v2:
   Make a local copy of the list

Signed-off-by: Emily Deng <Emily.Deng at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 2a21267..8c81404 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -3105,6 +3105,9 @@ static int amdgpu_device_handle_vram_lost(struct amdgpu_device *adev)
 	long r = 1;
 	int i = 0;
 	long tmo;
+	struct list_head local_shadow_list;
+
+	INIT_LIST_HEAD(&local_shadow_list);
 
 	if (amdgpu_sriov_runtime(adev))
 		tmo = msecs_to_jiffies(8000);
@@ -3112,8 +3115,19 @@ static int amdgpu_device_handle_vram_lost(struct amdgpu_device *adev)
 		tmo = msecs_to_jiffies(100);
 
 	DRM_INFO("recover vram bo from shadow start\n");
+
+	mutex_lock(&adev->shadow_list_lock);
+	list_splice_init(&adev->shadow_list, &local_shadow_list);
+	mutex_unlock(&adev->shadow_list_lock);
+
+
 	mutex_lock(&adev->shadow_list_lock);
-	list_for_each_entry_safe(bo, tmp, &adev->shadow_list, shadow_list) {
+	list_for_each_entry_safe(bo, tmp, &local_shadow_list, shadow_list) {
+		mutex_unlock(&adev->shadow_list_lock);
+
+		if (!bo)
+			continue;
+
 		next = NULL;
 		amdgpu_device_recover_vram_from_shadow(adev, ring, bo, &next);
 		if (fence) {
@@ -3132,9 +3146,14 @@ static int amdgpu_device_handle_vram_lost(struct amdgpu_device *adev)
 
 		dma_fence_put(fence);
 		fence = next;
+		mutex_lock(&adev->shadow_list_lock);
 	}
 	mutex_unlock(&adev->shadow_list_lock);
 
+	mutex_lock(&adev->shadow_list_lock);
+	list_splice_init(&local_shadow_list, &adev->shadow_list);
+	mutex_unlock(&adev->shadow_list_lock);
+
 	if (fence) {
 		r = dma_fence_wait_timeout(fence, false, tmo);
 		if (r == 0)
-- 
2.7.4