habanalabs: Assign each CQ with its own work queue

We identified a possible race during job completion when working
with a single multi-threaded work queue. In order to overcome this
race we suggest using a single threaded work queue per completion
queue, hence we guarantee jobs completion in order.

Signed-off-by: Ofir Bitton <obitton@habana.ai>
Reviewed-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>

drivers/misc/habanalabs/command_submission.c

@@ -487,10 +487,12 @@ static void cs_rollback(struct hl_device *hdev, struct hl_cs *cs)
 
 void hl_cs_rollback_all(struct hl_device *hdev)
 {
+	int i;
 	struct hl_cs *cs, *tmp;
 
 	/* flush all completions */
-	flush_workqueue(hdev->cq_wq);
+	for (i = 0 ; i < hdev->asic_prop.completion_queues_count ; i++)
+		flush_workqueue(hdev->cq_wq[i]);
 
 	/* Make sure we don't have leftovers in the H/W queues mirror list */
 	list_for_each_entry_safe(cs, tmp, &hdev->hw_queues_mirror_list,

drivers/misc/habanalabs/device.c

@@ -249,7 +249,8 @@ static void device_cdev_sysfs_del(struct hl_device *hdev)
  */
 static int device_early_init(struct hl_device *hdev)
 {
-	int rc;
+	int i, rc;
+	char workq_name[32];
 
 	switch (hdev->asic_type) {
 	case ASIC_GOYA:
@@ -274,11 +275,24 @@ static int device_early_init(struct hl_device *hdev)
 	if (rc)
 		goto early_fini;
 
-	hdev->cq_wq = alloc_workqueue("hl-free-jobs", WQ_UNBOUND, 0);
-	if (hdev->cq_wq == NULL) {
-		dev_err(hdev->dev, "Failed to allocate CQ workqueue\n");
-		rc = -ENOMEM;
-		goto asid_fini;
+	if (hdev->asic_prop.completion_queues_count) {
+		hdev->cq_wq = kcalloc(hdev->asic_prop.completion_queues_count,
+				sizeof(*hdev->cq_wq),
+				GFP_ATOMIC);
+		if (!hdev->cq_wq) {
+			rc = -ENOMEM;
+			goto asid_fini;
+		}
+	}
+
+	for (i = 0 ; i < hdev->asic_prop.completion_queues_count ; i++) {
+		snprintf(workq_name, 32, "hl-free-jobs-%u", i);
+		hdev->cq_wq[i] = create_singlethread_workqueue(workq_name);
+		if (hdev->cq_wq == NULL) {
+			dev_err(hdev->dev, "Failed to allocate CQ workqueue\n");
+			rc = -ENOMEM;
+			goto free_cq_wq;
+		}
 	}
 
 	hdev->eq_wq = alloc_workqueue("hl-events", WQ_UNBOUND, 0);
@@ -321,7 +335,10 @@ static int device_early_init(struct hl_device *hdev)
 free_eq_wq:
 	destroy_workqueue(hdev->eq_wq);
 free_cq_wq:
-	destroy_workqueue(hdev->cq_wq);
+	for (i = 0 ; i < hdev->asic_prop.completion_queues_count ; i++)
+		if (hdev->cq_wq[i])
+			destroy_workqueue(hdev->cq_wq[i]);
+	kfree(hdev->cq_wq);
 asid_fini:
 	hl_asid_fini(hdev);
 early_fini:
@@ -339,6 +356,8 @@ static int device_early_init(struct hl_device *hdev)
  */
 static void device_early_fini(struct hl_device *hdev)
 {
+	int i;
+
 	mutex_destroy(&hdev->mmu_cache_lock);
 	mutex_destroy(&hdev->debug_lock);
 	mutex_destroy(&hdev->send_cpu_message_lock);
@@ -351,7 +370,10 @@ static void device_early_fini(struct hl_device *hdev)
 	kfree(hdev->hl_chip_info);
 
 	destroy_workqueue(hdev->eq_wq);
-	destroy_workqueue(hdev->cq_wq);
+
+	for (i = 0 ; i < hdev->asic_prop.completion_queues_count ; i++)
+		destroy_workqueue(hdev->cq_wq[i]);
+	kfree(hdev->cq_wq);
 
 	hl_asid_fini(hdev);
 
@@ -1181,6 +1203,7 @@ int hl_device_init(struct hl_device *hdev, struct class *hclass)
 				"failed to initialize completion queue\n");
 			goto cq_fini;
 		}
+		hdev->completion_queue[i].cq_idx = i;
 	}
 
 	/*

drivers/misc/habanalabs/habanalabs.h

@@ -479,6 +479,7 @@ struct hl_hw_queue {
  * @hdev: pointer to the device structure
  * @kernel_address: holds the queue's kernel virtual address
  * @bus_address: holds the queue's DMA address
+ * @cq_idx: completion queue index in array
  * @hw_queue_id: the id of the matching H/W queue
  * @ci: ci inside the queue
  * @pi: pi inside the queue
@@ -488,6 +489,7 @@ struct hl_cq {
 	struct hl_device	*hdev;
 	u64			kernel_address;
 	dma_addr_t		bus_address;
+	u32			cq_idx;
 	u32			hw_queue_id;
 	u32			ci;
 	u32			pi;
@@ -1396,7 +1398,8 @@ struct hl_device_idle_busy_ts {
  * @asic_name: ASIC specific nmae.
  * @asic_type: ASIC specific type.
  * @completion_queue: array of hl_cq.
- * @cq_wq: work queue of completion queues for executing work in process context
+ * @cq_wq: work queues of completion queues for executing work in process
+ *         context.
  * @eq_wq: work queue of event queue for executing work in process context.
  * @kernel_ctx: Kernel driver context structure.
  * @kernel_queues: array of hl_hw_queue.
@@ -1492,7 +1495,7 @@ struct hl_device {
 	char				asic_name[16];
 	enum hl_asic_type		asic_type;
 	struct hl_cq			*completion_queue;
-	struct workqueue_struct		*cq_wq;
+	struct workqueue_struct		**cq_wq;
 	struct workqueue_struct		*eq_wq;
 	struct hl_ctx			*kernel_ctx;
 	struct hl_hw_queue		*kernel_queues;

drivers/misc/habanalabs/irq.c

@@ -119,7 +119,7 @@ irqreturn_t hl_irq_handler_cq(int irq, void *arg)
 
 		if ((shadow_index_valid) && (!hdev->disabled)) {
 			job = queue->shadow_queue[hl_pi_2_offset(shadow_index)];
-			queue_work(hdev->cq_wq, &job->finish_work);
+			queue_work(hdev->cq_wq[cq->cq_idx], &job->finish_work);
 		}
 
 		atomic_inc(&queue->ci);