s390/con3270: add special output handling when oops_in_progress is set

Normally a user can scroll back with PF7/PF8 if printed messages are
outside of the visible screen area. This doesn't work when the kernel
crashes, because the scrollback handling is done by the kernel, which
is no longer alive after the kernel crash. Add code to always print
all dirty lines in the screen buffer, so the user can scroll back with
the terminal scrollback keys (Page Up/Down).
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

drivers/s390/char/con3270.c

@@ -91,6 +91,7 @@ struct tty3270 {
 	char *converted_line;		/* RAW 3270 data stream */
 	unsigned int line_view_start;	/* Start of visible area */
 	unsigned int line_write_start;	/* current write position */
+	unsigned int oops_line;		/* line counter used when print oops */
 
 	/* Current tty screen. */
 	unsigned int cx, cy;		/* Current output position. */
@@ -129,7 +130,8 @@ struct tty3270 {
 /* tty3270->update_flags. See tty3270_update for details. */
 #define TTY_UPDATE_INPUT	0x1	/* Update input line. */
 #define TTY_UPDATE_STATUS	0x2	/* Update status line. */
-#define TTY_UPDATE_ALL		0x3	/* Recreate screen. */
+#define TTY_UPDATE_LINES	0x4	/* Update visible screen lines */
+#define TTY_UPDATE_ALL		0x7	/* Recreate screen. */
 
 #define TTY3270_INPUT_AREA_ROWS 2
 
@@ -274,7 +276,7 @@ static int tty3270_add_status(struct tty3270 *tp)
 		codepage_convert(tp->view.ascebc, cp, len);
 		cp += len;
 	} else {
-		cp = tty3270_ebcdic_convert(tp, cp, "Running");
+		cp = tty3270_ebcdic_convert(tp, cp, oops_in_progress ? "Crashed" : "Running");
 	}
 	cp = tty3270_add_sf(tp, cp, TF_LOG);
 	cp = tty3270_add_sa(tp, cp, TAT_FGCOLOR, TAC_RESET);
@@ -468,6 +470,55 @@ static unsigned int tty3270_convert_line(struct tty3270 *tp, struct tty3270_line
 	return cp - (char *)tp->converted_line;
 }
 
+static void tty3270_update_lines_visible(struct tty3270 *tp, struct raw3270_request *rq)
+{
+	struct tty3270_line *line;
+	int len, i;
+
+	for (i = 0; i < tty3270_tty_rows(tp); i++) {
+		line = tty3270_get_view_line(tp, i);
+		if (!line->dirty)
+			continue;
+		len = tty3270_convert_line(tp, line, i);
+		if (raw3270_request_add_data(rq, tp->converted_line, len))
+			break;
+		line->dirty = 0;
+	}
+	if (i == tty3270_tty_rows(tp)) {
+		for (i = 0; i < tp->allocated_lines; i++)
+			tp->screen[i].dirty = 0;
+		tp->update_flags &= ~TTY_UPDATE_LINES;
+	}
+}
+
+static void tty3270_update_lines_all(struct tty3270 *tp, struct raw3270_request *rq)
+{
+	struct tty3270_line *line;
+	char buf[4];
+	int len, i;
+
+	for (i = 0; i < tp->allocated_lines; i++) {
+		line = tty3270_get_write_line(tp, i + tp->cy + 1);
+		if (!line->dirty)
+			continue;
+		len = tty3270_convert_line(tp, line, tp->oops_line);
+		if (raw3270_request_add_data(rq, tp->converted_line, len))
+			break;
+		line->dirty = 0;
+		if (++tp->oops_line >= tty3270_tty_rows(tp))
+			tp->oops_line = 0;
+	}
+
+	if (i == tp->allocated_lines) {
+		if (tp->oops_line < tty3270_tty_rows(tp)) {
+			tty3270_add_ra(tp, buf, 0, tty3270_tty_rows(tp), 0);
+			if (raw3270_request_add_data(rq, buf, sizeof(buf)))
+				return;
+		}
+		tp->update_flags &= ~TTY_UPDATE_LINES;
+	}
+}
+
 /*
  * Update 3270 display.
  */
@@ -475,9 +526,8 @@ static void tty3270_update(struct timer_list *t)
 {
 	struct tty3270 *tp = from_timer(tp, t, timer);
 	struct raw3270_request *wrq;
-	struct tty3270_line *line;
 	u8 cmd = TC_WRITE;
-	int i, rc, len;
+	int rc, len;
 
 	wrq = xchg(&tp->write, 0);
 	if (!wrq) {
@@ -511,19 +561,13 @@ static void tty3270_update(struct timer_list *t)
 			tp->update_flags &= ~TTY_UPDATE_INPUT;
 	}
 
-	for (i = 0; i < tty3270_tty_rows(tp); i++) {
-		line = tty3270_get_view_line(tp, i);
-		if (!line->dirty)
-			continue;
-		len = tty3270_convert_line(tp, line, i);
-		if (raw3270_request_add_data(wrq, tp->converted_line, len))
-			break;
-		line->dirty = 0;
+	if (tp->update_flags & TTY_UPDATE_LINES) {
+		if (oops_in_progress)
+			tty3270_update_lines_all(tp, wrq);
+		else
+			tty3270_update_lines_visible(tp, wrq);
 	}
 
-	if (i < tty3270_tty_rows(tp) - 1)
-		tty3270_set_timer(tp, 1);
-
 	wrq->callback = tty3270_write_callback;
 	rc = raw3270_start(&tp->view, wrq);
 	if (rc == 0) {
@@ -1750,6 +1794,7 @@ static void tty3270_do_write(struct tty3270 *tp, struct tty_struct *tty,
 		}
 	}
 	/* Setup timer to update display after 1/10 second */
+	tp->update_flags |= TTY_UPDATE_LINES;
 	if (!timer_pending(&tp->timer))
 		tty3270_set_timer(tp, msecs_to_jiffies(100));
 
@@ -2068,6 +2113,7 @@ static int con3270_notify(struct notifier_block *self,
 		return NOTIFY_DONE;
 	con3270_wait_write(tp);
 	tp->nr_up = 0;
+	tp->update_flags = TTY_UPDATE_ALL;
 	while (tp->update_flags != 0) {
 		spin_unlock_irqrestore(&tp->view.lock, flags);
 		tty3270_update(&tp->timer);