[S390] cio: unsolicited interrupts during sense pgid.

Calls to set a device online with path grouping may get stuck in
some cases because certain device conditions where discarded after
unsolicited interrupts.
Check subchannel activity after unsolicited interrupts and retry
the operation if the subchannel is idle.
Signed-off-by: Stefan Bader <shbader@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/cio/device_pgid.c

@@ -23,6 +23,21 @@
 #include "device.h"
 #include "ioasm.h"
 
+/*
+ * Helper function called from interrupt context to decide whether an
+ * operation should be tried again.
+ */
+static int __ccw_device_should_retry(struct scsw *scsw)
+{
+	/* CC is only valid if start function bit is set. */
+	if ((scsw->fctl & SCSW_FCTL_START_FUNC) && scsw->cc == 1)
+		return 1;
+	/* No more activity. For sense and set PGID we stubbornly try again. */
+	if (!scsw->actl)
+		return 1;
+	return 0;
+}
+
 /*
  * Start Sense Path Group ID helper function. Used in ccw_device_recog
  * and ccw_device_sense_pgid.
@@ -155,10 +170,10 @@ ccw_device_sense_pgid_irq(struct ccw_device *cdev, enum dev_event dev_event)
 	int ret;
 
 	irb = (struct irb *) __LC_IRB;
-	/* Retry sense pgid for cc=1. */
+
 	if (irb->scsw.stctl ==
 	    (SCSW_STCTL_STATUS_PEND | SCSW_STCTL_ALERT_STATUS)) {
-		if (irb->scsw.cc == 1) {
+		if (__ccw_device_should_retry(&irb->scsw)) {
 			ret = __ccw_device_sense_pgid_start(cdev);
 			if (ret && ret != -EBUSY)
 				ccw_device_sense_pgid_done(cdev, ret);
@@ -391,10 +406,10 @@ ccw_device_verify_irq(struct ccw_device *cdev, enum dev_event dev_event)
 	int ret;
 
 	irb = (struct irb *) __LC_IRB;
-	/* Retry set pgid for cc=1. */
+
 	if (irb->scsw.stctl ==
 	    (SCSW_STCTL_STATUS_PEND | SCSW_STCTL_ALERT_STATUS)) {
-		if (irb->scsw.cc == 1)
+		if (__ccw_device_should_retry(&irb->scsw))
 			__ccw_device_verify_start(cdev);
 		return;
 	}
@@ -494,10 +509,10 @@ ccw_device_disband_irq(struct ccw_device *cdev, enum dev_event dev_event)
 	int ret;
 
 	irb = (struct irb *) __LC_IRB;
-	/* Retry set pgid for cc=1. */
+
 	if (irb->scsw.stctl ==
 	    (SCSW_STCTL_STATUS_PEND | SCSW_STCTL_ALERT_STATUS)) {
-		if (irb->scsw.cc == 1)
+		if (__ccw_device_should_retry(&irb->scsw))
 			__ccw_device_disband_start(cdev);
 		return;
 	}