[PATCH] [2.5] Non-blocking write can block

[P. Benie]

Non-blocking writes to a tty will block if there is a blocking write
waiting for the atomic_write semaphore.

Peter

--- linux-2.5.70/drivers/char/tty_io.c.orig	2003-06-03 21:34:42.000000000 +0100
+++ linux-2.5.70/drivers/char/tty_io.c	2003-06-04 01:40:33.000000000 +0100
@@ -687,8 +687,13 @@
 {
 	ssize_t ret = 0, written = 0;

-	if (down_interruptible(&tty->atomic_write)) {
-		return -ERESTARTSYS;
+	if (file->f_flags & O_NONBLOCK) {
+		if (down_trylock(&tty->atomic_write))
+			return -EAGAIN;
+	}
+	else {
+		if (down_interruptible(&tty->atomic_write))
+			return -ERESTARTSYS;
 	}
 	if ( test_bit(TTY_NO_WRITE_SPLIT, &tty->flags) ) {
 		lock_kernel();