RDMA/hns: Fix soft lockup under heavy CEQE load

CEQEs are handled in interrupt handler currently. This may cause the
CPU core staying in interrupt context too long and lead to soft lockup
under heavy load.

Handle CEQEs in BH workqueue and set an upper limit for the number of
CEQE handled by a single call of work handler.

Fixes: a5073d6 ("RDMA/hns: Add eq support of hip08")
Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
Link: https://lore.kernel.org/r/20240710133705.896445-3-huangjunxian6@hisilicon.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>

Author: Junxian Huang

drivers/infiniband/hw/hns/hns_roce_device.h

@@ -717,6 +717,7 @@ struct hns_roce_eq {
 	int				shift;
 	int				event_type;
 	int				sub_type;
+	struct work_struct		work;
 };
 
 struct hns_roce_eq_table {

drivers/infiniband/hw/hns/hns_roce_hw_v2.c

@@ -36,6 +36,7 @@
 #include <linux/iopoll.h>
 #include <linux/kernel.h>
 #include <linux/types.h>
+#include <linux/workqueue.h>
 #include <net/addrconf.h>
 #include <rdma/ib_addr.h>
 #include <rdma/ib_cache.h>
@@ -6140,33 +6141,11 @@ static struct hns_roce_ceqe *next_ceqe_sw_v2(struct hns_roce_eq *eq)
 		!!(eq->cons_index & eq->entries)) ? ceqe : NULL;
 }
 
-static irqreturn_t hns_roce_v2_ceq_int(struct hns_roce_dev *hr_dev,
-				       struct hns_roce_eq *eq)
+static irqreturn_t hns_roce_v2_ceq_int(struct hns_roce_eq *eq)
 {
-	struct hns_roce_ceqe *ceqe = next_ceqe_sw_v2(eq);
-	irqreturn_t ceqe_found = IRQ_NONE;
-	u32 cqn;
-
-	while (ceqe) {
-		/* Make sure we read CEQ entry after we have checked the
-		 * ownership bit
-		 */
-		dma_rmb();
-
-		cqn = hr_reg_read(ceqe, CEQE_CQN);
-
-		hns_roce_cq_completion(hr_dev, cqn);
-
-		++eq->cons_index;
-		ceqe_found = IRQ_HANDLED;
-		atomic64_inc(&hr_dev->dfx_cnt[HNS_ROCE_DFX_CEQE_CNT]);
-
-		ceqe = next_ceqe_sw_v2(eq);
-	}
+	queue_work(system_bh_wq, &eq->work);
 
-	update_eq_db(eq);
-
-	return IRQ_RETVAL(ceqe_found);
+	return IRQ_HANDLED;
 }
 
 static irqreturn_t hns_roce_v2_msix_interrupt_eq(int irq, void *eq_ptr)
@@ -6177,7 +6156,7 @@ static irqreturn_t hns_roce_v2_msix_interrupt_eq(int irq, void *eq_ptr)
 
 	if (eq->type_flag == HNS_ROCE_CEQ)
 		/* Completion event interrupt */
-		int_work = hns_roce_v2_ceq_int(hr_dev, eq);
+		int_work = hns_roce_v2_ceq_int(eq);
 	else
 		/* Asynchronous event interrupt */
 		int_work = hns_roce_v2_aeq_int(hr_dev, eq);
@@ -6545,6 +6524,34 @@ static int hns_roce_v2_create_eq(struct hns_roce_dev *hr_dev,
 	return ret;
 }
 
+static void hns_roce_ceq_work(struct work_struct *work)
+{
+	struct hns_roce_eq *eq = from_work(eq, work, work);
+	struct hns_roce_ceqe *ceqe = next_ceqe_sw_v2(eq);
+	struct hns_roce_dev *hr_dev = eq->hr_dev;
+	int ceqe_num = 0;
+	u32 cqn;
+
+	while (ceqe && ceqe_num < hr_dev->caps.ceqe_depth) {
+		/* Make sure we read CEQ entry after we have checked the
+		 * ownership bit
+		 */
+		dma_rmb();
+
+		cqn = hr_reg_read(ceqe, CEQE_CQN);
+
+		hns_roce_cq_completion(hr_dev, cqn);
+
+		++eq->cons_index;
+		++ceqe_num;
+		atomic64_inc(&hr_dev->dfx_cnt[HNS_ROCE_DFX_CEQE_CNT]);
+
+		ceqe = next_ceqe_sw_v2(eq);
+	}
+
+	update_eq_db(eq);
+}
+
 static int __hns_roce_request_irq(struct hns_roce_dev *hr_dev, int irq_num,
 				  int comp_num, int aeq_num, int other_num)
 {
@@ -6576,21 +6583,24 @@ static int __hns_roce_request_irq(struct hns_roce_dev *hr_dev, int irq_num,
 			 j - other_num - aeq_num);
 
 	for (j = 0; j < irq_num; j++) {
-		if (j < other_num)
+		if (j < other_num) {
 			ret = request_irq(hr_dev->irq[j],
 					  hns_roce_v2_msix_interrupt_abn,
 					  0, hr_dev->irq_names[j], hr_dev);
-
-		else if (j < (other_num + comp_num))
+		} else if (j < (other_num + comp_num)) {
+			INIT_WORK(&eq_table->eq[j - other_num].work,
+				  hns_roce_ceq_work);
 			ret = request_irq(eq_table->eq[j - other_num].irq,
 					  hns_roce_v2_msix_interrupt_eq,
 					  0, hr_dev->irq_names[j + aeq_num],
 					  &eq_table->eq[j - other_num]);
-		else
+		} else {
 			ret = request_irq(eq_table->eq[j - other_num].irq,
 					  hns_roce_v2_msix_interrupt_eq,
 					  0, hr_dev->irq_names[j - comp_num],
 					  &eq_table->eq[j - other_num]);
+		}
+
 		if (ret) {
 			dev_err(hr_dev->dev, "request irq error!\n");
 			goto err_request_failed;
@@ -6600,12 +6610,16 @@ static int __hns_roce_request_irq(struct hns_roce_dev *hr_dev, int irq_num,
 	return 0;
 
 err_request_failed:
-	for (j -= 1; j >= 0; j--)
-		if (j < other_num)
+	for (j -= 1; j >= 0; j--) {
+		if (j < other_num) {
 			free_irq(hr_dev->irq[j], hr_dev);
-		else
-			free_irq(eq_table->eq[j - other_num].irq,
-				 &eq_table->eq[j - other_num]);
+			continue;
+		}
+		free_irq(eq_table->eq[j - other_num].irq,
+			 &eq_table->eq[j - other_num]);
+		if (j < other_num + comp_num)
+			cancel_work_sync(&eq_table->eq[j - other_num].work);
+	}
 
 err_kzalloc_failed:
 	for (i -= 1; i >= 0; i--)
@@ -6626,8 +6640,11 @@ static void __hns_roce_free_irq(struct hns_roce_dev *hr_dev)
 	for (i = 0; i < hr_dev->caps.num_other_vectors; i++)
 		free_irq(hr_dev->irq[i], hr_dev);
 
-	for (i = 0; i < eq_num; i++)
+	for (i = 0; i < eq_num; i++) {
 		free_irq(hr_dev->eq_table.eq[i].irq, &hr_dev->eq_table.eq[i]);
+		if (i < hr_dev->caps.num_comp_vectors)
+			cancel_work_sync(&hr_dev->eq_table.eq[i].work);
+	}
 
 	for (i = 0; i < irq_num; i++)
 		kfree(hr_dev->irq_names[i]);