drm/amdgpu: race issue when jobs on 2 ring timeout

Fix a racing issue when jobs on 2 rings timeout simultaneously.

If 2 rings timed out at the same time, the
amdgpu_device_gpu_recover will be reentered. Then the
adev->gmc.xgmi.head will be grabbed by 2 local linked list,
which may cause wild pointer issue in iterating.

lock the device earily to prevent the node be added to 2
different lists.

also increase karma for the skipped job since the job is also
timed out and should be guilty.

Signed-off-by: Horace Chen <[e-mail]>
Reviewed-by: Andrey Grodzovsky <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu_device.c

···
 	up_write(&adev->reset_sem);
 }
 
+/*
+ * to lockup a list of amdgpu devices in a hive safely, if not a hive
+ * with multiple nodes, it will be similar as amdgpu_device_lock_adev.
+ *
+ * unlock won't require roll back.
+ */
+static int amdgpu_device_lock_hive_adev(struct amdgpu_device *adev, struct amdgpu_hive_info *hive)
+{
+	struct amdgpu_device *tmp_adev = NULL;
+
+	if (adev->gmc.xgmi.num_physical_nodes > 1) {
+		if (!hive) {
+			dev_err(adev->dev, "Hive is NULL while device has multiple xgmi nodes");
+			return -ENODEV;
+		}
+		list_for_each_entry(tmp_adev, &hive->device_list, gmc.xgmi.head) {
+			if (!amdgpu_device_lock_adev(tmp_adev, hive))
+				goto roll_back;
+		}
+	} else if (!amdgpu_device_lock_adev(adev, hive))
+		return -EAGAIN;
+
+	return 0;
+roll_back:
+	if (!list_is_first(&tmp_adev->gmc.xgmi.head, &hive->device_list)) {
+		/*
+		 * if the lockup iteration break in the middle of a hive,
+		 * it may means there may has a race issue,
+		 * or a hive device locked up independently.
+		 * we may be in trouble and may not, so will try to roll back
+		 * the lock and give out a warnning.
+		 */
+		dev_warn(tmp_adev->dev, "Hive lock iteration broke in the middle. Rolling back to unlock");
+		list_for_each_entry_continue_reverse(tmp_adev, &hive->device_list, gmc.xgmi.head) {
+			amdgpu_device_unlock_adev(tmp_adev);
+		}
+	}
+	return -EAGAIN;
+}
+
 static void amdgpu_device_resume_display_audio(struct amdgpu_device *adev)
 {
 	struct pci_dev *p = NULL;
···
 			DRM_INFO("Bailing on TDR for s_job:%llx, hive: %llx as another already in progress",
 				job ? job->base.id : -1, hive->hive_id);
 			amdgpu_put_xgmi_hive(hive);
+			if (job)
+				drm_sched_increase_karma(&job->base);
 			return 0;
 		}
 		mutex_lock(&hive->hive_lock);
+	}
+
+	/*
+	 * lock the device before we try to operate the linked list
+	 * if didn't get the device lock, don't touch the linked list since
+	 * others may iterating it.
+	 */
+	r = amdgpu_device_lock_hive_adev(adev, hive);
+	if (r) {
+		dev_info(adev->dev, "Bailing on TDR for s_job:%llx, as another already in progress",
+					job ? job->base.id : -1);
+
+		/* even we skipped this reset, still need to set the job to guilty */
+		if (job)
+			drm_sched_increase_karma(&job->base);
+		goto skip_recovery;
 	}
 
 	/*
···
 	 */
 	INIT_LIST_HEAD(&device_list);
 	if (adev->gmc.xgmi.num_physical_nodes > 1) {
-		if (!hive)
-			return -ENODEV;
 		if (!list_is_first(&adev->gmc.xgmi.head, &hive->device_list))
 			list_rotate_to_front(&adev->gmc.xgmi.head, &hive->device_list);
 		device_list_handle = &hive->device_list;
···
 
 	/* block all schedulers and reset given job's ring */
 	list_for_each_entry(tmp_adev, device_list_handle, gmc.xgmi.head) {
-		if (!amdgpu_device_lock_adev(tmp_adev, hive)) {
-			dev_info(tmp_adev->dev, "Bailing on TDR for s_job:%llx, as another already in progress",
-				  job ? job->base.id : -1);
-			r = 0;
-			goto skip_recovery;
-		}
-
 		/*
 		 * Try to put the audio codec into suspend state
 		 * before gpu reset started.
···
 		amdgpu_put_xgmi_hive(hive);
 	}
 
-	if (r)
+	if (r && r != -EAGAIN)
 		dev_info(adev->dev, "GPU reset end with ret = %d\n", r);
 	return r;
 }