tty: introduce wait_event_interruptible_tty

Calling wait_event_interruptible implicitly
releases the BKL when it sleeps, but we need
to do this explcitly when we have converted
it to a mutex.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/char/istallion.c b/drivers/char/istallion.c
index 5e9a81d..be28391 100644
--- a/drivers/char/istallion.c
+++ b/drivers/char/istallion.c
@@ -954,7 +954,7 @@
  *	order of opens and closes may not be preserved across shared
  *	memory, so we must wait until it is complete.
  */
-	wait_event_interruptible(portp->raw_wait,
+	wait_event_interruptible_tty(portp->raw_wait,
 			!test_bit(ST_CLOSING, &portp->state));
 	if (signal_pending(current)) {
 		return -ERESTARTSYS;
@@ -989,7 +989,7 @@
 	set_bit(ST_OPENING, &portp->state);
 	spin_unlock_irqrestore(&brd_lock, flags);
 
-	wait_event_interruptible(portp->raw_wait,
+	wait_event_interruptible_tty(portp->raw_wait,
 			!test_bit(ST_OPENING, &portp->state));
 	if (signal_pending(current))
 		rc = -ERESTARTSYS;
@@ -1020,7 +1020,7 @@
  *	occurs on this port.
  */
 	if (wait) {
-		wait_event_interruptible(portp->raw_wait,
+		wait_event_interruptible_tty(portp->raw_wait,
 				!test_bit(ST_CLOSING, &portp->state));
 		if (signal_pending(current)) {
 			return -ERESTARTSYS;
@@ -1052,7 +1052,7 @@
  *	to come back.
  */
 	rc = 0;
-	wait_event_interruptible(portp->raw_wait,
+	wait_event_interruptible_tty(portp->raw_wait,
 			!test_bit(ST_CLOSING, &portp->state));
 	if (signal_pending(current))
 		rc = -ERESTARTSYS;
@@ -1073,6 +1073,10 @@
 
 static int stli_cmdwait(struct stlibrd *brdp, struct stliport *portp, unsigned long cmd, void *arg, int size, int copyback)
 {
+	/*
+	 * no need for wait_event_tty because clearing ST_CMDING cannot block
+	 * on BTM
+	 */
 	wait_event_interruptible(portp->raw_wait,
 			!test_bit(ST_CMDING, &portp->state));
 	if (signal_pending(current))