r4796 - trunk/varnish-cache/bin/varnishd

[phk at varnish-cache.org]

Author: phk
Date: 2010-05-17 10:40:08 +0200 (Mon, 17 May 2010)
New Revision: 4796

Modified:
   trunk/varnish-cache/bin/varnishd/common.h
Log:
Add preliminary macro for memory barriers



Modified: trunk/varnish-cache/bin/varnishd/common.h
===================================================================
--- trunk/varnish-cache/bin/varnishd/common.h	2010-05-17 08:11:43 UTC (rev 4795)
+++ trunk/varnish-cache/bin/varnishd/common.h	2010-05-17 08:40:08 UTC (rev 4796)
@@ -70,3 +70,18 @@
 };
 
 #define NEEDLESS_RETURN(foo)	return (foo)
+
+/**********************************************************************
+ * Guess what:  There is no POSIX standard for memory barriers.
+ * XXX: Please try to find the minimal #ifdef to use here, rely on OS
+ * supplied facilities if at all possible, to avoid descending into the
+ * full cpu/compiler explosion.
+ */
+
+#ifdef __FreeBSD__
+#include <machine/atomic.h>
+#define MEMORY_BARRIER()       mb()
+#else
+#warn "MEMORY_BARRIER() is expensive"
+#define MEMORY_BARRIER()       close(-1)
+#endif