s390/3270: avoid endless I/O loop with disconnected 3270 terminals

If a 3270 terminal is disconnected while the tty view is active
the 3270 driver goes into an endless loop of failed I/O requests
until the terminal is connected again.

Add code to the raw3270 interrupt handler to check for unit checks
due to failed I/O requests and put the device to sleep with the
RAW3270_FLAGS_BUSY flag until a unsolicited device end interrupt
indicates that the device can be used again. while we are at it
simplify the 3270 irq handling and remove unnecessary code.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/char/con3270.c

@@ -400,7 +400,7 @@ con3270_deactivate(struct raw3270_view *view)
 	del_timer(&cp->timer);
 }
 
-static int
+static void
 con3270_irq(struct con3270 *cp, struct raw3270_request *rq, struct irb *irb)
 {
 	/* Handle ATTN. Schedule tasklet to read aid. */
@@ -418,7 +418,6 @@ con3270_irq(struct con3270 *cp, struct raw3270_request *rq, struct irb *irb)
 		cp->update_flags = CON_UPDATE_ALL;
 		con3270_set_timer(cp, 1);
 	}
-	return RAW3270_IO_DONE;
 }
 
 /* Console view to a 3270 device. */

drivers/s390/char/fs3270.c

@@ -217,7 +217,7 @@ fs3270_deactivate(struct raw3270_view *view)
 		fp->init->callback(fp->init, NULL);
 }
 
-static int
+static void
 fs3270_irq(struct fs3270 *fp, struct raw3270_request *rq, struct irb *irb)
 {
 	/* Handle ATTN. Set indication and wake waiters for attention. */
@@ -233,7 +233,6 @@ fs3270_irq(struct fs3270 *fp, struct raw3270_request *rq, struct irb *irb)
 			/* Normal end. Copy residual count. */
 			rq->rescnt = irb->scsw.cmd.count;
 	}
-	return RAW3270_IO_DONE;
 }
 
 /*

drivers/s390/char/raw3270.c

@@ -228,29 +228,6 @@ raw3270_request_set_idal(struct raw3270_request *rq, struct idal_buffer *ib)
 	rq->ccw.flags |= CCW_FLAG_IDA;
 }
 
-/*
- * Stop running ccw.
- */
-static int
-__raw3270_halt_io(struct raw3270 *rp, struct raw3270_request *rq)
-{
-	int retries;
-	int rc;
-
-	if (raw3270_request_final(rq))
-		return 0;
-	/* Check if interrupt has already been processed */
-	for (retries = 0; retries < 5; retries++) {
-		if (retries < 2)
-			rc = ccw_device_halt(rp->cdev, (long) rq);
-		else
-			rc = ccw_device_clear(rp->cdev, (long) rq);
-		if (rc == 0)
-			break;		/* termination successful */
-	}
-	return rc;
-}
-
 /*
  * Add the request to the request queue, try to start it if the
  * 3270 device is idle. Return without waiting for end of i/o.
@@ -342,7 +319,6 @@ raw3270_irq (struct ccw_device *cdev, unsigned long intparm, struct irb *irb)
 	struct raw3270 *rp;
 	struct raw3270_view *view;
 	struct raw3270_request *rq;
-	int rc;
 
 	rp = dev_get_drvdata(&cdev->dev);
 	if (!rp)
@@ -350,55 +326,27 @@ raw3270_irq (struct ccw_device *cdev, unsigned long intparm, struct irb *irb)
 	rq = (struct raw3270_request *) intparm;
 	view = rq ? rq->view : rp->view;
 
-	if (IS_ERR(irb))
-		rc = RAW3270_IO_RETRY;
-	else if (irb->scsw.cmd.fctl & SCSW_FCTL_HALT_FUNC) {
-		rq->rc = -EIO;
-		rc = RAW3270_IO_DONE;
-	} else if (irb->scsw.cmd.dstat == (DEV_STAT_CHN_END | DEV_STAT_DEV_END |
-					   DEV_STAT_UNIT_EXCEP)) {
+	if (!IS_ERR(irb)) {
 		/* Handle CE-DE-UE and subsequent UDE */
-		set_bit(RAW3270_FLAGS_BUSY, &rp->flags);
-		rc = RAW3270_IO_BUSY;
-	} else if (test_bit(RAW3270_FLAGS_BUSY, &rp->flags)) {
-		/* Wait for UDE if busy flag is set. */
-		if (irb->scsw.cmd.dstat & DEV_STAT_DEV_END) {
+		if (irb->scsw.cmd.dstat & DEV_STAT_DEV_END)
 			clear_bit(RAW3270_FLAGS_BUSY, &rp->flags);
-			/* Got it, now retry. */
-			rc = RAW3270_IO_RETRY;
-		} else
-			rc = RAW3270_IO_BUSY;
-	} else if (view)
-		rc = view->fn->intv(view, rq, irb);
-	else
-		rc = RAW3270_IO_DONE;
+		if (irb->scsw.cmd.dstat == (DEV_STAT_CHN_END |
+					    DEV_STAT_DEV_END |
+					    DEV_STAT_UNIT_EXCEP))
+			set_bit(RAW3270_FLAGS_BUSY, &rp->flags);
+		/* Handle disconnected devices */
+		if ((irb->scsw.cmd.dstat & DEV_STAT_UNIT_CHECK) &&
+		    (irb->ecw[0] & SNS0_INTERVENTION_REQ))
+			set_bit(RAW3270_FLAGS_BUSY, &rp->flags);
+		/* Call interrupt handler of the view */
+		if (view)
+			view->fn->intv(view, rq, irb);
+	}
 
-	switch (rc) {
-	case RAW3270_IO_DONE:
-		break;
-	case RAW3270_IO_BUSY:
-		/* 
-		 * Intervention required by the operator. We have to wait
-		 * for unsolicited device end.
-		 */
+	if (test_bit(RAW3270_FLAGS_BUSY, &rp->flags))
+		/* Device busy, do not start I/O */
 		return;
-	case RAW3270_IO_RETRY:
-		if (!rq)
-			break;
-		rq->rc = ccw_device_start(rp->cdev, &rq->ccw,
-					  (unsigned long) rq, 0, 0);
-		if (rq->rc == 0)
-			return;	/* Successfully restarted. */
-		break;
-	case RAW3270_IO_STOP:
-		if (!rq)
-			break;
-		__raw3270_halt_io(rp, rq);
-		rq->rc = -EIO;
-		break;
-	default:
-		BUG();
-	}
+
 	if (rq) {
 		BUG_ON(list_empty(&rq->list));
 		/* The request completed, remove from queue and do callback. */
@@ -408,6 +356,7 @@ raw3270_irq (struct ccw_device *cdev, unsigned long intparm, struct irb *irb)
 		/* Do put_device for get_device in raw3270_start. */
 		raw3270_put_view(view);
 	}
+
 	/*
 	 * Try to start each request on request queue until one is
 	 * started successful.
@@ -685,23 +634,12 @@ raw3270_reset(struct raw3270_view *view)
 	return rc;
 }
 
-static int
+static void
 raw3270_init_irq(struct raw3270_view *view, struct raw3270_request *rq,
 		 struct irb *irb)
 {
 	struct raw3270 *rp;
 
-	/*
-	 * Unit-Check Processing:
-	 * Expect Command Reject or Intervention Required.
-	 */
-	if (irb->scsw.cmd.dstat & DEV_STAT_UNIT_CHECK) {
-		/* Request finished abnormally. */
-		if (irb->ecw[0] & SNS0_INTERVENTION_REQ) {
-			set_bit(RAW3270_FLAGS_BUSY, &view->dev->flags);
-			return RAW3270_IO_BUSY;
-		}
-	}
 	if (rq) {
 		if (irb->scsw.cmd.dstat & DEV_STAT_UNIT_CHECK) {
 			if (irb->ecw[0] & SNS0_CMD_REJECT)
@@ -715,7 +653,6 @@ raw3270_init_irq(struct raw3270_view *view, struct raw3270_request *rq,
 		rp = view->dev;
 		raw3270_read_modified(rp);
 	}
-	return RAW3270_IO_DONE;
 }
 
 static struct raw3270_fn raw3270_init_fn = {

drivers/s390/char/raw3270.h

@@ -125,19 +125,13 @@ raw3270_request_final(struct raw3270_request *rq)
 
 void raw3270_buffer_address(struct raw3270 *, char *, unsigned short);
 
-/* Return value of *intv (see raw3270_fn below) can be one of the following: */
-#define RAW3270_IO_DONE		0	/* request finished */
-#define RAW3270_IO_BUSY		1	/* request still active */
-#define RAW3270_IO_RETRY	2	/* retry current request */
-#define RAW3270_IO_STOP		3	/* kill current request */
-
 /*
  * Functions of a 3270 view.
  */
 struct raw3270_fn {
 	int  (*activate)(struct raw3270_view *);
 	void (*deactivate)(struct raw3270_view *);
-	int  (*intv)(struct raw3270_view *,
+	void (*intv)(struct raw3270_view *,
 		     struct raw3270_request *, struct irb *);
 	void (*release)(struct raw3270_view *);
 	void (*free)(struct raw3270_view *);

drivers/s390/char/tty3270.c

@@ -645,7 +645,7 @@ tty3270_deactivate(struct raw3270_view *view)
 	del_timer(&tp->timer);
 }
 
-static int
+static void
 tty3270_irq(struct tty3270 *tp, struct raw3270_request *rq, struct irb *irb)
 {
 	/* Handle ATTN. Schedule tasklet to read aid. */
@@ -667,7 +667,6 @@ tty3270_irq(struct tty3270 *tp, struct raw3270_request *rq, struct irb *irb)
 		tp->update_flags = TTY_UPDATE_ALL;
 		tty3270_set_timer(tp, 1);
 	}
-	return RAW3270_IO_DONE;
 }
 
 /*