From f7027c6387d0c3acf569845165ec7947e2083c82 Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Fri, 12 Jun 2009 22:27:00 -0600 Subject: [PATCH] lguest: get more serious about wmb() in example Launcher code Since the Launcher process runs the Guest, it doesn't have to be very serious about its barriers: the Guest isn't running while we are (Guest is UP). Before we change to use threads to service devices, we need to fix this. Signed-off-by: Rusty Russell --- Documentation/lguest/lguest.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c index 1a2b906..1e31d1e 100644 --- a/Documentation/lguest/lguest.c +++ b/Documentation/lguest/lguest.c @@ -182,9 +182,10 @@ struct virtqueue /* Remember the arguments to the program so we can "reboot" */ static char **main_args; -/* Since guest is UP and we don't run at the same time, we don't need barriers. - * But I include them in the code in case others copy it. */ -#define wmb() +/* We have to be careful with barriers: our devices are all run in separate + * threads and so we need to make sure that changes visible to the Guest happen + * in precise order. */ +#define wmb() __asm__ __volatile__("" : : : "memory") /* Convert an iovec element to the given type. * -- 2.7.4