From 2b4c03cbc84090174a3cf5d27887bac8fb052b57 Mon Sep 17 00:00:00 2001
From: Justus Winter <4winter@informatik.uni-hamburg.de>
Date: Mon, 7 Sep 2015 14:37:40 +0200
Subject: kern: fix loop reading the time value

Previously, recent versions of gcc would hoist the loads out of the
loop reading the time value.

* kern/macros.h (access_once): New macro.
* kern/mach_clock.c (host_get_time): Use the new macro to prevent the
loads from being hoisted out of the loop.
---
 kern/macros.h | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'kern/macros.h')

diff --git a/kern/macros.h b/kern/macros.h
index 7cc579d..c2e8545 100644
--- a/kern/macros.h
+++ b/kern/macros.h
@@ -52,6 +52,8 @@
 #define structof(ptr, type, member) \
     ((type *)((char *)(ptr) - offsetof(type, member)))
 
+#define access_once(x)      (*(volatile typeof(x) *)&(x))
+
 #define alignof(x)          __alignof__(x)
 
 #ifndef likely
-- 
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