s390/ap: fix state machine hang after failure to enable irq

If for any reason the interrupt enable for an ap queue fails the
state machine run for the queue returned wrong return codes to the
caller. So the caller assumed interrupt support for this queue in
enabled and thus did not re-establish the high resolution timer used
for polling. In the end this let to a hang for the user space process
waiting "forever" for the reply.

This patch reworks these return codes to return correct indications
for the caller to re-establish the timer when a queue runs without
interrupt support.

Please note that this is fixing a wrong behavior after a first
failure (enable interrupt support for the queue) failed. However,
looks like this occasionally happens on KVM systems.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

1 files changed, 8 insertions, 17 deletions

diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
index c7c4d00ab1ce..439c1f6d2866 100644
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -127,7 +127,7 @@ static struct bus_type ap_bus_type;
 /* Adapter interrupt definitions */
 static void ap_interrupt_handler(struct airq_struct *airq, bool floating);
 
-static int ap_airq_flag;
+static bool ap_irq_flag;
 
 static struct airq_struct ap_airq = {
 	.handler = ap_interrupt_handler,
@@ -135,15 +135,6 @@ static struct airq_struct ap_airq = {
 };
 
 /**
- * ap_using_interrupts() - Returns non-zero if interrupt support is
- * available.
- */
-static inline int ap_using_interrupts(void)
-{
-	return ap_airq_flag;
-}
-
-/**
  * ap_airq_ptr() - Get the address of the adapter interrupt indicator
  *
  * Returns the address of the local-summary-indicator of the adapter
@@ -152,7 +143,7 @@ static inline int ap_using_interrupts(void)
  */
 void *ap_airq_ptr(void)
 {
-	if (ap_using_interrupts())
+	if (ap_irq_flag)
 		return ap_airq.lsi_ptr;
 	return NULL;
 }
@@ -396,7 +387,7 @@ void ap_wait(enum ap_sm_wait wait)
 	switch (wait) {
 	case AP_SM_WAIT_AGAIN:
 	case AP_SM_WAIT_INTERRUPT:
-		if (ap_using_interrupts())
+		if (ap_irq_flag)
 			break;
 		if (ap_poll_kthread) {
 			wake_up(&ap_poll_wait);
@@ -471,7 +462,7 @@ static void ap_tasklet_fn(unsigned long dummy)
 	 * be received. Doing it in the beginning of the tasklet is therefor
 	 * important that no requests on any AP get lost.
 	 */
-	if (ap_using_interrupts())
+	if (ap_irq_flag)
 		xchg(ap_airq.lsi_ptr, 0);
 
 	spin_lock_bh(&ap_queues_lock);
@@ -541,7 +532,7 @@ static int ap_poll_thread_start(void)
 {
 	int rc;
 
-	if (ap_using_interrupts() || ap_poll_kthread)
+	if (ap_irq_flag || ap_poll_kthread)
 		return 0;
 	mutex_lock(&ap_poll_thread_mutex);
 	ap_poll_kthread = kthread_run(ap_poll_thread, NULL, "appoll");
@@ -1184,7 +1175,7 @@ static BUS_ATTR_RO(ap_adapter_mask);
 static ssize_t ap_interrupts_show(struct bus_type *bus, char *buf)
 {
 	return scnprintf(buf, PAGE_SIZE, "%d\n",
-			 ap_using_interrupts() ? 1 : 0);
+			 ap_irq_flag ? 1 : 0);
 }
 
 static BUS_ATTR_RO(ap_interrupts);
@@ -1909,7 +1900,7 @@ static int __init ap_module_init(void)
 	/* enable interrupts if available */
 	if (ap_interrupts_available()) {
 		rc = register_adapter_interrupt(&ap_airq);
-		ap_airq_flag = (rc == 0);
+		ap_irq_flag = (rc == 0);
 	}
 
 	/* Create /sys/bus/ap. */
@@ -1953,7 +1944,7 @@ out_work:
 out_bus:
 	bus_unregister(&ap_bus_type);
 out:
-	if (ap_using_interrupts())
+	if (ap_irq_flag)
 		unregister_adapter_interrupt(&ap_airq);
 	kfree(ap_qci_info);
 	return rc;