From 687696162fafe4e17f1a01631f7deb16f72ec5f6 Mon Sep 17 00:00:00 2001
From: sgehwolf <unknown>
Date: Tue, 24 Feb 2015 21:17:59 -0500
Subject: [PATCH] 8067331: Zero: Atomic::xchg and Atomic::xchg_ptr need full
 memory barrier Reviewed-by: dholmes, coleenp

---
 .../bsd_zero/vm/atomic_bsd_zero.inline.hpp       | 12 ++++++++++--
 .../linux_zero/vm/atomic_linux_zero.inline.hpp   | 16 ++++++++++++----
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/src/os_cpu/bsd_zero/vm/atomic_bsd_zero.inline.hpp b/src/os_cpu/bsd_zero/vm/atomic_bsd_zero.inline.hpp
index 4ed293446..6bc5f1e10 100644
--- a/src/os_cpu/bsd_zero/vm/atomic_bsd_zero.inline.hpp
+++ b/src/os_cpu/bsd_zero/vm/atomic_bsd_zero.inline.hpp
@@ -238,7 +238,13 @@ inline jint Atomic::xchg(jint exchange_value, volatile jint* dest) {
   // operation.  Note that some platforms only support this with the
   // limitation that the only valid value to store is the immediate
   // constant 1.  There is a test for this in JNI_CreateJavaVM().
-  return __sync_lock_test_and_set (dest, exchange_value);
+  jint result = __sync_lock_test_and_set (dest, exchange_value);
+  // All atomic operations are expected to be full memory barriers
+  // (see atomic.hpp). However, __sync_lock_test_and_set is not
+  // a full memory barrier, but an acquire barrier. Hence, this added
+  // barrier.
+  __sync_synchronize();
+  return result;
 #endif // M68K
 #endif // ARM
 }
@@ -251,7 +257,9 @@ inline intptr_t Atomic::xchg_ptr(intptr_t exchange_value,
 #ifdef M68K
   return m68k_lock_test_and_set(dest, exchange_value);
 #else
-  return __sync_lock_test_and_set (dest, exchange_value);
+  intptr_t result = __sync_lock_test_and_set (dest, exchange_value);
+  __sync_synchronize();
+  return result;
 #endif // M68K
 #endif // ARM
 }
diff --git a/src/os_cpu/linux_zero/vm/atomic_linux_zero.inline.hpp b/src/os_cpu/linux_zero/vm/atomic_linux_zero.inline.hpp
index 33ce50dc7..b7aca02e0 100644
--- a/src/os_cpu/linux_zero/vm/atomic_linux_zero.inline.hpp
+++ b/src/os_cpu/linux_zero/vm/atomic_linux_zero.inline.hpp
@@ -1,6 +1,6 @@
 /*
- * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
- * Copyright 2007, 2008, 2011 Red Hat, Inc.
+ * Copyright (c) 2003, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright 2007, 2008, 2011, 2015, Red Hat, Inc.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -232,7 +232,13 @@ inline jint Atomic::xchg(jint exchange_value, volatile jint* dest) {
   // operation.  Note that some platforms only support this with the
   // limitation that the only valid value to store is the immediate
   // constant 1.  There is a test for this in JNI_CreateJavaVM().
-  return __sync_lock_test_and_set (dest, exchange_value);
+  jint result = __sync_lock_test_and_set (dest, exchange_value);
+  // All atomic operations are expected to be full memory barriers
+  // (see atomic.hpp). However, __sync_lock_test_and_set is not
+  // a full memory barrier, but an acquire barrier. Hence, this added
+  // barrier.
+  __sync_synchronize();
+  return result;
 #endif // M68K
 #endif // ARM
 }
@@ -245,7 +251,9 @@ inline intptr_t Atomic::xchg_ptr(intptr_t exchange_value,
 #ifdef M68K
   return m68k_lock_test_and_set(dest, exchange_value);
 #else
-  return __sync_lock_test_and_set (dest, exchange_value);
+  intptr_t result = __sync_lock_test_and_set (dest, exchange_value);
+  __sync_synchronize();
+  return result;
 #endif // M68K
 #endif // ARM
 }
-- 
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