[SCSI] ibmvfc: Fix soft lockup on resume

This fixes a softlockup seen on resume. During resume, the CRQ
must be reenabled. However, the H_ENABLE_CRQ hcall used to do
this may return H_BUSY or H_LONG_BUSY. When this happens, the
caller is expected to retry later. Normally the H_ENABLE_CRQ
succeeds relatively soon. However, we have seen cases where
this can take long enough to see softlockup warnings.
This patch changes a simple loop, which was causing the
softlockup, to a loop at task level which sleeps between
retries rather than simply spinning.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/ibmvscsi/ibmvfc.c

@@ -504,12 +504,23 @@ static void ibmvfc_set_host_action(struct ibmvfc_host *vhost,
 		if (vhost->action == IBMVFC_HOST_ACTION_ALLOC_TGTS)
 			vhost->action = action;
 		break;
-	case IBMVFC_HOST_ACTION_LOGO:
 	case IBMVFC_HOST_ACTION_INIT:
 	case IBMVFC_HOST_ACTION_TGT_DEL:
+		switch (vhost->action) {
+		case IBMVFC_HOST_ACTION_RESET:
+		case IBMVFC_HOST_ACTION_REENABLE:
+			break;
+		default:
+			vhost->action = action;
+			break;
+		};
+		break;
+	case IBMVFC_HOST_ACTION_LOGO:
 	case IBMVFC_HOST_ACTION_QUERY_TGTS:
 	case IBMVFC_HOST_ACTION_TGT_DEL_FAILED:
 	case IBMVFC_HOST_ACTION_NONE:
+	case IBMVFC_HOST_ACTION_RESET:
+	case IBMVFC_HOST_ACTION_REENABLE:
 	default:
 		vhost->action = action;
 		break;
@@ -641,7 +652,7 @@ static int ibmvfc_send_crq_init_complete(struct ibmvfc_host *vhost)
  **/
 static void ibmvfc_release_crq_queue(struct ibmvfc_host *vhost)
 {
-	long rc;
+	long rc = 0;
 	struct vio_dev *vdev = to_vio_dev(vhost->dev);
 	struct ibmvfc_crq_queue *crq = &vhost->crq;
 
@@ -649,6 +660,8 @@ static void ibmvfc_release_crq_queue(struct ibmvfc_host *vhost)
 	free_irq(vdev->irq, vhost);
 	tasklet_kill(&vhost->tasklet);
 	do {
+		if (rc)
+			msleep(100);
 		rc = plpar_hcall_norets(H_FREE_CRQ, vdev->unit_address);
 	} while (rc == H_BUSY || H_IS_LONG_BUSY(rc));
 
@@ -667,11 +680,13 @@ static void ibmvfc_release_crq_queue(struct ibmvfc_host *vhost)
  **/
 static int ibmvfc_reenable_crq_queue(struct ibmvfc_host *vhost)
 {
-	int rc;
+	int rc = 0;
 	struct vio_dev *vdev = to_vio_dev(vhost->dev);
 
 	/* Re-enable the CRQ */
 	do {
+		if (rc)
+			msleep(100);
 		rc = plpar_hcall_norets(H_ENABLE_CRQ, vdev->unit_address);
 	} while (rc == H_IN_PROGRESS || rc == H_BUSY || H_IS_LONG_BUSY(rc));
 
@@ -690,15 +705,19 @@ static int ibmvfc_reenable_crq_queue(struct ibmvfc_host *vhost)
  **/
 static int ibmvfc_reset_crq(struct ibmvfc_host *vhost)
 {
-	int rc;
+	int rc = 0;
+	unsigned long flags;
 	struct vio_dev *vdev = to_vio_dev(vhost->dev);
 	struct ibmvfc_crq_queue *crq = &vhost->crq;
 
 	/* Close the CRQ */
 	do {
+		if (rc)
+			msleep(100);
 		rc = plpar_hcall_norets(H_FREE_CRQ, vdev->unit_address);
 	} while (rc == H_BUSY || H_IS_LONG_BUSY(rc));
 
+	spin_lock_irqsave(vhost->host->host_lock, flags);
 	vhost->state = IBMVFC_NO_CRQ;
 	vhost->logged_in = 0;
 	ibmvfc_set_host_action(vhost, IBMVFC_HOST_ACTION_NONE);
@@ -716,6 +735,7 @@ static int ibmvfc_reset_crq(struct ibmvfc_host *vhost)
 		dev_warn(vhost->dev, "Partner adapter not ready\n");
 	else if (rc != 0)
 		dev_warn(vhost->dev, "Couldn't register crq (rc=%d)\n", rc);
+	spin_unlock_irqrestore(vhost->host->host_lock, flags);
 
 	return rc;
 }
@@ -821,17 +841,9 @@ static void ibmvfc_purge_requests(struct ibmvfc_host *vhost, int error_code)
  **/
 static void ibmvfc_hard_reset_host(struct ibmvfc_host *vhost)
 {
-	int rc;
-
-	scsi_block_requests(vhost->host);
 	ibmvfc_purge_requests(vhost, DID_ERROR);
-	if ((rc = ibmvfc_reset_crq(vhost)) ||
-	    (rc = ibmvfc_send_crq_init(vhost)) ||
-	    (rc = vio_enable_interrupts(to_vio_dev(vhost->dev)))) {
-		dev_err(vhost->dev, "Error after reset rc=%d\n", rc);
-		ibmvfc_link_down(vhost, IBMVFC_LINK_DEAD);
-	} else
-		ibmvfc_link_down(vhost, IBMVFC_LINK_DOWN);
+	ibmvfc_link_down(vhost, IBMVFC_LINK_DOWN);
+	ibmvfc_set_host_action(vhost, IBMVFC_HOST_ACTION_RESET);
 }
 
 /**
@@ -2606,22 +2618,13 @@ static void ibmvfc_handle_crq(struct ibmvfc_crq *crq, struct ibmvfc_host *vhost)
 			dev_info(vhost->dev, "Re-enabling adapter\n");
 			vhost->client_migrated = 1;
 			ibmvfc_purge_requests(vhost, DID_REQUEUE);
-			if ((rc = ibmvfc_reenable_crq_queue(vhost)) ||
-			    (rc = ibmvfc_send_crq_init(vhost))) {
-				ibmvfc_link_down(vhost, IBMVFC_LINK_DEAD);
-				dev_err(vhost->dev, "Error after enable (rc=%ld)\n", rc);
-			} else
-				ibmvfc_link_down(vhost, IBMVFC_LINK_DOWN);
+			ibmvfc_link_down(vhost, IBMVFC_LINK_DOWN);
+			ibmvfc_set_host_action(vhost, IBMVFC_HOST_ACTION_REENABLE);
 		} else {
 			dev_err(vhost->dev, "Virtual adapter failed (rc=%d)\n", crq->format);
-
 			ibmvfc_purge_requests(vhost, DID_ERROR);
-			if ((rc = ibmvfc_reset_crq(vhost)) ||
-			    (rc = ibmvfc_send_crq_init(vhost))) {
-				ibmvfc_link_down(vhost, IBMVFC_LINK_DEAD);
-				dev_err(vhost->dev, "Error after reset (rc=%ld)\n", rc);
-			} else
-				ibmvfc_link_down(vhost, IBMVFC_LINK_DOWN);
+			ibmvfc_link_down(vhost, IBMVFC_LINK_DOWN);
+			ibmvfc_set_host_action(vhost, IBMVFC_HOST_ACTION_RESET);
 		}
 		return;
 	case IBMVFC_CRQ_CMD_RSP:
@@ -4123,6 +4126,8 @@ static int __ibmvfc_work_to_do(struct ibmvfc_host *vhost)
 	case IBMVFC_HOST_ACTION_TGT_DEL:
 	case IBMVFC_HOST_ACTION_TGT_DEL_FAILED:
 	case IBMVFC_HOST_ACTION_QUERY:
+	case IBMVFC_HOST_ACTION_RESET:
+	case IBMVFC_HOST_ACTION_REENABLE:
 	default:
 		break;
 	};
@@ -4220,6 +4225,7 @@ static void ibmvfc_do_work(struct ibmvfc_host *vhost)
 	struct ibmvfc_target *tgt;
 	unsigned long flags;
 	struct fc_rport *rport;
+	int rc;
 
 	ibmvfc_log_ae(vhost, vhost->events_to_log);
 	spin_lock_irqsave(vhost->host->host_lock, flags);
@@ -4229,6 +4235,27 @@ static void ibmvfc_do_work(struct ibmvfc_host *vhost)
 	case IBMVFC_HOST_ACTION_LOGO_WAIT:
 	case IBMVFC_HOST_ACTION_INIT_WAIT:
 		break;
+	case IBMVFC_HOST_ACTION_RESET:
+		vhost->action = IBMVFC_HOST_ACTION_TGT_DEL;
+		spin_unlock_irqrestore(vhost->host->host_lock, flags);
+		rc = ibmvfc_reset_crq(vhost);
+		spin_lock_irqsave(vhost->host->host_lock, flags);
+		if (rc || (rc = ibmvfc_send_crq_init(vhost)) ||
+		    (rc = vio_enable_interrupts(to_vio_dev(vhost->dev)))) {
+			ibmvfc_link_down(vhost, IBMVFC_LINK_DEAD);
+			dev_err(vhost->dev, "Error after reset (rc=%d)\n", rc);
+		}
+		break;
+	case IBMVFC_HOST_ACTION_REENABLE:
+		vhost->action = IBMVFC_HOST_ACTION_TGT_DEL;
+		spin_unlock_irqrestore(vhost->host->host_lock, flags);
+		rc = ibmvfc_reenable_crq_queue(vhost);
+		spin_lock_irqsave(vhost->host->host_lock, flags);
+		if (rc || (rc = ibmvfc_send_crq_init(vhost))) {
+			ibmvfc_link_down(vhost, IBMVFC_LINK_DEAD);
+			dev_err(vhost->dev, "Error after enable (rc=%d)\n", rc);
+		}
+		break;
 	case IBMVFC_HOST_ACTION_LOGO:
 		vhost->job_step(vhost);
 		break;

drivers/scsi/ibmvscsi/ibmvfc.h

@@ -649,6 +649,8 @@ struct ibmvfc_event_pool {
 
 enum ibmvfc_host_action {
 	IBMVFC_HOST_ACTION_NONE = 0,
+	IBMVFC_HOST_ACTION_RESET,
+	IBMVFC_HOST_ACTION_REENABLE,
 	IBMVFC_HOST_ACTION_LOGO,
 	IBMVFC_HOST_ACTION_LOGO_WAIT,
 	IBMVFC_HOST_ACTION_INIT,