RDMA/bnxt_re: Avoid system hang during device un-reg

BNXT_RE_FLAG_TASK_IN_PROG doesn't handle multiple work
requests posted together. Track schedule of multiple
workqueue items by maintaining a per device counter
and proceed with IB dereg only if this counter is zero.
flush_workqueue is no longer required from
NETDEV_UNREGISTER path.
Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/bnxt_re/bnxt_re.h

@@ -120,7 +120,6 @@ struct bnxt_re_dev {
 #define BNXT_RE_FLAG_HAVE_L2_REF		3
 #define BNXT_RE_FLAG_RCFW_CHANNEL_EN		4
 #define BNXT_RE_FLAG_QOS_WORK_REG		5
-#define BNXT_RE_FLAG_TASK_IN_PROG		6
 #define BNXT_RE_FLAG_ISSUE_ROCE_STATS          29
 	struct net_device		*netdev;
 	unsigned int			version, major, minor;
@@ -158,6 +157,7 @@ struct bnxt_re_dev {
 	atomic_t			srq_count;
 	atomic_t			mr_count;
 	atomic_t			mw_count;
+	atomic_t			sched_count;
 	/* Max of 2 lossless traffic class supported per port */
 	u16				cosq[2];
 

drivers/infiniband/hw/bnxt_re/main.c

@@ -656,7 +656,6 @@ static void bnxt_re_dev_remove(struct bnxt_re_dev *rdev)
 	mutex_unlock(&bnxt_re_dev_lock);
 
 	synchronize_rcu();
-	flush_workqueue(bnxt_re_wq);
 
 	ib_dealloc_device(&rdev->ibdev);
 	/* rdev is gone */
@@ -1441,7 +1440,7 @@ static void bnxt_re_task(struct work_struct *work)
 		break;
 	}
 	smp_mb__before_atomic();
-	clear_bit(BNXT_RE_FLAG_TASK_IN_PROG, &rdev->flags);
+	atomic_dec(&rdev->sched_count);
 	kfree(re_work);
 }
 
@@ -1503,7 +1502,7 @@ static int bnxt_re_netdev_event(struct notifier_block *notifier,
 		/* netdev notifier will call NETDEV_UNREGISTER again later since
 		 * we are still holding the reference to the netdev
 		 */
-		if (test_bit(BNXT_RE_FLAG_TASK_IN_PROG, &rdev->flags))
+		if (atomic_read(&rdev->sched_count) > 0)
 			goto exit;
 		bnxt_re_ib_unreg(rdev, false);
 		bnxt_re_remove_one(rdev);
@@ -1523,7 +1522,7 @@ static int bnxt_re_netdev_event(struct notifier_block *notifier,
 			re_work->vlan_dev = (real_dev == netdev ?
 					     NULL : netdev);
 			INIT_WORK(&re_work->work, bnxt_re_task);
-			set_bit(BNXT_RE_FLAG_TASK_IN_PROG, &rdev->flags);
+			atomic_inc(&rdev->sched_count);
 			queue_work(bnxt_re_wq, &re_work->work);
 		}
 	}