qeth: fix qeth_wait_for_threads() deadlock for OSN devices

Any recovery thread will deadlock when calling qeth_wait_for_threads(), most
notably when triggering a recovery on an OSN device.
This patch will store the recovery thread's task pointer on recovery
invocation and check in qeth_wait_for_threads() respectively to avoid
deadlocks.

Signed-off-by: Stefan Raspl <raspl@linux.vnet.ibm.com>
Signed-off-by: Frank Blaschka <blaschka@linux.vnet.ibm.com>
Reviewed-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/qeth_core.h

@@ -769,6 +769,7 @@ struct qeth_card {
 	unsigned long thread_start_mask;
 	unsigned long thread_allowed_mask;
 	unsigned long thread_running_mask;
+	struct task_struct *recovery_task;
 	spinlock_t ip_lock;
 	struct list_head ip_list;
 	struct list_head *ip_tbd_list;
@@ -862,6 +863,8 @@ extern struct qeth_card_list_struct qeth_core_card_list;
 extern struct kmem_cache *qeth_core_header_cache;
 extern struct qeth_dbf_info qeth_dbf[QETH_DBF_INFOS];
 
+void qeth_set_recovery_task(struct qeth_card *);
+void qeth_clear_recovery_task(struct qeth_card *);
 void qeth_set_allowed_threads(struct qeth_card *, unsigned long , int);
 int qeth_threads_running(struct qeth_card *, unsigned long);
 int qeth_wait_for_threads(struct qeth_card *, unsigned long);

drivers/s390/net/qeth_core_main.c

@@ -177,6 +177,23 @@ const char *qeth_get_cardname_short(struct qeth_card *card)
 	return "n/a";
 }
 
+void qeth_set_recovery_task(struct qeth_card *card)
+{
+	card->recovery_task = current;
+}
+EXPORT_SYMBOL_GPL(qeth_set_recovery_task);
+
+void qeth_clear_recovery_task(struct qeth_card *card)
+{
+	card->recovery_task = NULL;
+}
+EXPORT_SYMBOL_GPL(qeth_clear_recovery_task);
+
+static bool qeth_is_recovery_task(const struct qeth_card *card)
+{
+	return card->recovery_task == current;
+}
+
 void qeth_set_allowed_threads(struct qeth_card *card, unsigned long threads,
 			 int clear_start_mask)
 {
@@ -205,6 +222,8 @@ EXPORT_SYMBOL_GPL(qeth_threads_running);
 
 int qeth_wait_for_threads(struct qeth_card *card, unsigned long threads)
 {
+	if (qeth_is_recovery_task(card))
+		return 0;
 	return wait_event_interruptible(card->wait_q,
 			qeth_threads_running(card, threads) == 0);
 }

drivers/s390/net/qeth_l2_main.c

@@ -1143,6 +1143,7 @@ static int qeth_l2_recover(void *ptr)
 	QETH_CARD_TEXT(card, 2, "recover2");
 	dev_warn(&card->gdev->dev,
 		"A recovery process has been started for the device\n");
+	qeth_set_recovery_task(card);
 	__qeth_l2_set_offline(card->gdev, 1);
 	rc = __qeth_l2_set_online(card->gdev, 1);
 	if (!rc)
@@ -1153,6 +1154,7 @@ static int qeth_l2_recover(void *ptr)
 		dev_warn(&card->gdev->dev, "The qeth device driver "
 				"failed to recover an error on the device\n");
 	}
+	qeth_clear_recovery_task(card);
 	qeth_clear_thread_start_bit(card, QETH_RECOVER_THREAD);
 	qeth_clear_thread_running_bit(card, QETH_RECOVER_THREAD);
 	return 0;

drivers/s390/net/qeth_l3_main.c

@@ -3515,6 +3515,7 @@ static int qeth_l3_recover(void *ptr)
 	QETH_CARD_TEXT(card, 2, "recover2");
 	dev_warn(&card->gdev->dev,
 		"A recovery process has been started for the device\n");
+	qeth_set_recovery_task(card);
 	__qeth_l3_set_offline(card->gdev, 1);
 	rc = __qeth_l3_set_online(card->gdev, 1);
 	if (!rc)
@@ -3525,6 +3526,7 @@ static int qeth_l3_recover(void *ptr)
 		dev_warn(&card->gdev->dev, "The qeth device driver "
 				"failed to recover an error on the device\n");
 	}
+	qeth_clear_recovery_task(card);
 	qeth_clear_thread_start_bit(card, QETH_RECOVER_THREAD);
 	qeth_clear_thread_running_bit(card, QETH_RECOVER_THREAD);
 	return 0;