From d7a855bd6ab25d10d5e3b6aeb53d9c57fa17b808 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Wed, 10 Sep 2014 15:06:30 -0400 Subject: [PATCH] tty: Convert tty_struct bitfield to ints The stopped, hw_stopped, flow_stopped and packet bits are smp-unsafe and interrupt-unsafe. For example, CPU 0 | CPU 1 | tty->flow_stopped = 1 | tty->hw_stopped = 0 One of these updates will be corrupted, as the bitwise operation on the bitfield is non-atomic. Ensure each flag has a separate memory location, so concurrent updates do not corrupt orthogonal states. Because DEC Alpha EV4 and EV5 cpus (from 1995) perform RMW on smaller-than-machine-word storage, "separate memory location" must be int instead of byte. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- include/linux/tty.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/include/linux/tty.h b/include/linux/tty.h index 84132942902a..4cfd4a82fc31 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -261,7 +261,10 @@ struct tty_struct { unsigned long flags; int count; struct winsize winsize; /* winsize_mutex */ - unsigned char stopped:1, hw_stopped:1, flow_stopped:1, packet:1; + int stopped; + int flow_stopped; + int hw_stopped; + int packet; unsigned char ctrl_status; /* ctrl_lock */ unsigned int receive_room; /* Bytes free for queue */ int flow_change; -- 2.20.1