[S390] cio: call ccw driver notify function with lock held

Calling a ccw driver's notify function without the ccw device lock
held opens up a race window between discovery and handling of a change
in the device operational state. As a result, the device driver may
encounter unexpected device malfunction, leading to out-of-retry
situations or similar.

Remove race by extending the ccw device lock from state change
discovery to the calling of the notify function.
Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/block/dasd.c

@@ -2333,13 +2333,11 @@ int dasd_generic_notify(struct ccw_device *cdev, int event)
 {
 	struct dasd_device *device;
 	struct dasd_ccw_req *cqr;
-	unsigned long flags;
 	int ret;
 
-	device = dasd_device_from_cdev(cdev);
+	device = dasd_device_from_cdev_locked(cdev);
 	if (IS_ERR(device))
 		return 0;
-	spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
 	ret = 0;
 	switch (event) {
 	case CIO_GONE:
@@ -2369,7 +2367,6 @@ int dasd_generic_notify(struct ccw_device *cdev, int event)
 		ret = 1;
 		break;
 	}
-	spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
 	dasd_put_device(device);
 	return ret;
 }

drivers/s390/cio/css.c

@@ -477,7 +477,6 @@ void css_schedule_eval_all(void)
 
 void css_wait_for_slow_path(void)
 {
-	flush_workqueue(ccw_device_notify_work);
 	flush_workqueue(slow_path_wq);
 }
 

drivers/s390/cio/device.c

@@ -150,7 +150,6 @@ static struct css_driver io_subchannel_driver = {
 };
 
 struct workqueue_struct *ccw_device_work;
-struct workqueue_struct *ccw_device_notify_work;
 wait_queue_head_t ccw_device_init_wq;
 atomic_t ccw_device_init_count;
 
@@ -168,11 +167,6 @@ init_ccw_bus_type (void)
 	ccw_device_work = create_singlethread_workqueue("cio");
 	if (!ccw_device_work)
 		return -ENOMEM; /* FIXME: better errno ? */
-	ccw_device_notify_work = create_singlethread_workqueue("cio_notify");
-	if (!ccw_device_notify_work) {
-		ret = -ENOMEM; /* FIXME: better errno ? */
-		goto out_err;
-	}
 	slow_path_wq = create_singlethread_workqueue("kslowcrw");
 	if (!slow_path_wq) {
 		ret = -ENOMEM; /* FIXME: better errno ? */
@@ -192,8 +186,6 @@ init_ccw_bus_type (void)
 out_err:
 	if (ccw_device_work)
 		destroy_workqueue(ccw_device_work);
-	if (ccw_device_notify_work)
-		destroy_workqueue(ccw_device_notify_work);
 	if (slow_path_wq)
 		destroy_workqueue(slow_path_wq);
 	return ret;
@@ -204,7 +196,6 @@ cleanup_ccw_bus_type (void)
 {
 	css_driver_unregister(&io_subchannel_driver);
 	bus_unregister(&ccw_bus_type);
-	destroy_workqueue(ccw_device_notify_work);
 	destroy_workqueue(ccw_device_work);
 }
 
@@ -1496,11 +1487,22 @@ static void device_set_disconnected(struct ccw_device *cdev)
 		ccw_device_schedule_recovery();
 }
 
+void ccw_device_set_notoper(struct ccw_device *cdev)
+{
+	struct subchannel *sch = to_subchannel(cdev->dev.parent);
+
+	CIO_TRACE_EVENT(2, "notoper");
+	CIO_TRACE_EVENT(2, sch->dev.bus_id);
+	ccw_device_set_timeout(cdev, 0);
+	cio_disable_subchannel(sch);
+	cdev->private->state = DEV_STATE_NOT_OPER;
+}
+
 static int io_subchannel_sch_event(struct subchannel *sch, int slow)
 {
 	int event, ret, disc;
 	unsigned long flags;
-	enum { NONE, UNREGISTER, UNREGISTER_PROBE, REPROBE } action;
+	enum { NONE, UNREGISTER, UNREGISTER_PROBE, REPROBE, DISC } action;
 	struct ccw_device *cdev;
 
 	spin_lock_irqsave(sch->lock, flags);
@@ -1535,16 +1537,11 @@ static int io_subchannel_sch_event(struct subchannel *sch, int slow)
 		}
 		/* fall through */
 	case CIO_GONE:
-		/* Prevent unwanted effects when opening lock. */
-		cio_disable_subchannel(sch);
-		device_set_disconnected(cdev);
 		/* Ask driver what to do with device. */
+		if (io_subchannel_notify(sch, event))
+			action = DISC;
+		else
 			action = UNREGISTER;
-		spin_unlock_irqrestore(sch->lock, flags);
-		ret = io_subchannel_notify(sch, event);
-		spin_lock_irqsave(sch->lock, flags);
-		if (ret)
-			action = NONE;
 		break;
 	case CIO_REVALIDATE:
 		/* Device will be removed, so no notify necessary. */
@@ -1565,6 +1562,7 @@ static int io_subchannel_sch_event(struct subchannel *sch, int slow)
 	switch (action) {
 	case UNREGISTER:
 	case UNREGISTER_PROBE:
+		ccw_device_set_notoper(cdev);
 		/* Unregister device (will use subchannel lock). */
 		spin_unlock_irqrestore(sch->lock, flags);
 		css_sch_device_unregister(sch);
@@ -1577,6 +1575,9 @@ static int io_subchannel_sch_event(struct subchannel *sch, int slow)
 	case REPROBE:
 		ccw_device_trigger_reprobe(cdev);
 		break;
+	case DISC:
+		device_set_disconnected(cdev);
+		break;
 	default:
 		break;
 	}
@@ -1828,5 +1829,4 @@ EXPORT_SYMBOL(ccw_driver_unregister);
 EXPORT_SYMBOL(get_ccwdev_by_busid);
 EXPORT_SYMBOL(ccw_bus_type);
 EXPORT_SYMBOL(ccw_device_work);
-EXPORT_SYMBOL(ccw_device_notify_work);
 EXPORT_SYMBOL_GPL(ccw_device_get_subchannel_id);

drivers/s390/cio/device.h

@@ -72,7 +72,6 @@ dev_fsm_final_state(struct ccw_device *cdev)
 }
 
 extern struct workqueue_struct *ccw_device_work;
-extern struct workqueue_struct *ccw_device_notify_work;
 extern wait_queue_head_t ccw_device_init_wq;
 extern atomic_t ccw_device_init_count;
 
@@ -120,6 +119,7 @@ int ccw_device_stlck(struct ccw_device *);
 void ccw_device_trigger_reprobe(struct ccw_device *);
 void ccw_device_kill_io(struct ccw_device *);
 int ccw_device_notify(struct ccw_device *, int);
+void ccw_device_set_notoper(struct ccw_device *cdev);
 
 /* qdio needs this. */
 void ccw_device_set_timeout(struct ccw_device *, int);

drivers/s390/cio/device_fsm.c

@@ -337,26 +337,34 @@ int ccw_device_notify(struct ccw_device *cdev, int event)
 		return 0;
 	if (!cdev->online)
 		return 0;
+	CIO_MSG_EVENT(2, "notify called for 0.%x.%04x, event=%d\n",
+		      cdev->private->dev_id.ssid, cdev->private->dev_id.devno,
+		      event);
 	return cdev->drv->notify ? cdev->drv->notify(cdev, event) : 0;
 }
 
-static void
-ccw_device_oper_notify(struct work_struct *work)
+static void cmf_reenable_delayed(struct work_struct *work)
 {
 	struct ccw_device_private *priv;
 	struct ccw_device *cdev;
-	int ret;
 
 	priv = container_of(work, struct ccw_device_private, kick_work);
 	cdev = priv->cdev;
-	ret = ccw_device_notify(cdev, CIO_OPER);
-	if (ret) {
-		/* Reenable channel measurements, if needed. */
 	cmf_reenable(cdev);
-		wake_up(&cdev->private->wait_q);
-	} else
+}
+
+static void ccw_device_oper_notify(struct ccw_device *cdev)
+{
+	if (ccw_device_notify(cdev, CIO_OPER)) {
+		/* Reenable channel measurements, if needed. */
+		PREPARE_WORK(&cdev->private->kick_work, cmf_reenable_delayed);
+		queue_work(ccw_device_work, &cdev->private->kick_work);
+		return;
+	}
 	/* Driver doesn't want device back. */
-		ccw_device_do_unreg_rereg(work);
+	ccw_device_set_notoper(cdev);
+	PREPARE_WORK(&cdev->private->kick_work, ccw_device_do_unreg_rereg);
+	queue_work(ccw_device_work, &cdev->private->kick_work);
 }
 
 /*
@@ -386,8 +394,7 @@ ccw_device_done(struct ccw_device *cdev, int state)
 
 	if (cdev->private->flags.donotify) {
 		cdev->private->flags.donotify = 0;
-		PREPARE_WORK(&cdev->private->kick_work, ccw_device_oper_notify);
-		queue_work(ccw_device_notify_work, &cdev->private->kick_work);
+		ccw_device_oper_notify(cdev);
 	}
 	wake_up(&cdev->private->wait_q);