Prevent an O_NDELAY writer from blocking when a tty write is blocked by the tty atomic writer mutex
Without this a tty write could block if a previous blocking tty write was
in progress on the same tty and blocked by a line discipline or hardware
event. Originally found and reported by Dave Johnson.
Signed-off-by: Alan Cox <alan@redhat.com>
Acked-by: Dave Johnson <djohnson+linux-kernel@sw.starentnetworks.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/tty.h b/include/linux/tty.h
index bb45760..deaba9e 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -338,6 +338,12 @@
extern struct mutex tty_mutex;
+extern void tty_write_unlock(struct tty_struct *tty);
+extern int tty_write_lock(struct tty_struct *tty, int ndelay);
+#define tty_is_writelocked(tty) (mutex_is_locked(&tty->atomic_write_lock))
+
+
+
/* n_tty.c */
extern struct tty_ldisc tty_ldisc_N_TTY;