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>

5 files changed, 23 insertions, 95 deletions

diff --git a/drivers/s390/char/con3270.c b/drivers/s390/char/con3270.c
index 4d7a9badfede..6b1577c73fe7 100644
--- a/drivers/s390/char/con3270.c
+++ b/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. */
diff --git a/drivers/s390/char/fs3270.c b/drivers/s390/char/fs3270.c
index 71e974738014..85eca1cef063 100644
--- a/drivers/s390/char/fs3270.c
+++ b/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;
 }
 
 /*
diff --git a/drivers/s390/char/raw3270.c b/drivers/s390/char/raw3270.c
index 220acb4cbee5..0743f13101ee 100644
--- a/drivers/s390/char/raw3270.c
+++ b/drivers/s390/char/raw3270.c
@@ -229,29 +229,6 @@ raw3270_request_set_idal(struct raw3270_request *rq, struct idal_buffer *ib)
 }
 
 /*
- * 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 = {
diff --git a/drivers/s390/char/raw3270.h b/drivers/s390/char/raw3270.h
index e1e41c2861fb..56519cbb165c 100644
--- a/drivers/s390/char/raw3270.h
+++ b/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 *);
diff --git a/drivers/s390/char/tty3270.c b/drivers/s390/char/tty3270.c
index 54ea5a01e30d..d6da18612ba8 100644
--- a/drivers/s390/char/tty3270.c
+++ b/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;
 }
 
 /*