From ca65d8a7fcc2217406320d4ae09a26bf68555632 Mon Sep 17 00:00:00 2001
From: Alan Cox <alan@linux.intel.com>
Date: Fri, 17 Aug 2018 10:44:49 +0100
Subject: [PATCH] tty: improve behaviour of O_NDELAY

We want to bale out on a polled output port on a reschedule not just sit
assuming the bits will go out shortly
---
 Kernel/tty.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/Kernel/tty.c b/Kernel/tty.c
index 169cd5ea..eba4444f 100644
--- a/Kernel/tty.c
+++ b/Kernel/tty.c
@@ -512,12 +512,14 @@ uint8_t tty_putc_maywait(uint8_t minor, unsigned char c, uint8_t flag)
 				udata.u_error = EINTR;
 				return 1;
 			}
-			if (t == TTY_READY_LATER && flag) {
-				udata.u_error = EAGAIN;
-				return 1;
-			}
 			if (t != TTY_READY_SOON || need_reschedule()){
-				irqflags_t irq = di();
+				irqflags_t irq;
+
+				if (flag) {
+					udata.u_error = EAGAIN;
+					return 1;
+				}
+				irq = di();
 				tty_sleeping(minor);
 				psleep(&ttydata[minor]);
 				irqrestore(irq);
-- 
2.34.1