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/drivers/char/n_tty.c b/drivers/char/n_tty.c
index 154f422..371631f 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -1538,7 +1538,8 @@
else
tty->minimum_to_wake = 1;
}
- if (tty->driver->chars_in_buffer(tty) < WAKEUP_CHARS &&
+ if (!tty_is_writelocked(tty) &&
+ tty->driver->chars_in_buffer(tty) < WAKEUP_CHARS &&
tty->driver->write_room(tty) > 0)
mask |= POLLOUT | POLLWRNORM;
return mask;