From f7027c6387d0c3acf569845165ec7947e2083c82 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
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 <rusty@rustcorp.com.au>
---
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 1a2b906a3ae6..1e31d1ec12a3 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.
*
--
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