From: Ben Pfaff <blp@cs.stanford.edu>
Date: Fri, 10 Nov 2006 15:51:03 +0000 (+0000)
Subject: Add "memory" as clobber to the asm used by barrier().
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2238c96ecda3b083eafbfcc3c2d8ebf2ade79d50;p=pintos-anon

Add "memory" as clobber to the asm used by barrier().
Otherwise at least some versions of GCC assume that no changes to
memory can take place.
---

diff --git a/src/threads/synch.h b/src/threads/synch.h
index 6b8f550..9e464e3 100644
--- a/src/threads/synch.h
+++ b/src/threads/synch.h
@@ -45,6 +45,6 @@ void cond_broadcast (struct condition *, struct lock *);
 
    The compiler will not reorder operations across an
    optimization barrier. */
-#define barrier() asm volatile ("")
+#define barrier() asm volatile ("" : : : "memory")
 
 #endif /* threads/synch.h */