Add membarrier call in Android.

src/shims/android_membarrier.h

@@ -0,0 +1,106 @@
+/*
+ * This source file is part of the Swift.org open source project
+ *
+ * Copyright (c) 2015 Apple Inc. and the Swift project authors
+ *
+ * Licensed under Apache License v2.0 with Runtime Library Exception
+ *
+ * See http://swift.org/LICENSE.txt for license information
+ * See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+ *
+ */
+
+// CUtil License:
+
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// membarrier definitionis taken from cutils/atomic-arm.h / cutils/atomic-x86.h 
+
+#ifndef __DISPATCH__ANDROID__MEMBARRIER_SHIMS__INTERNAL
+#define __DISPATCH__ANDROID__MEMBARRIER_SHIMS__INTERNAL
+
+#include <machine/cpu-features.h>
+
+extern inline void android_compiler_barrier(void)
+{
+    __asm__ __volatile__ ("" : : : "memory");
+}
+#if ANDROID_SMP == 0
+extern inline void android_memory_barrier(void)
+{
+    android_compiler_barrier();
+}
+extern inline void android_memory_store_barrier(void)
+{
+    android_compiler_barrier();
+}
+#elif defined(__i386__) || defined(__x86_64__)
+extern inline void android_memory_barrier(void)
+{
+    __asm__ __volatile__ ("mfence" : : : "memory");
+}
+extern inline void android_memory_store_barrier(void)
+{
+    android_compiler_barrier();
+}
+#elif defined(__arm__)
+#	if defined(__ARM_HAVE_DMB)
+extern inline void android_memory_barrier(void)
+{
+    __asm__ __volatile__ ("dmb" : : : "memory");
+}
+extern inline void android_memory_store_barrier(void)
+{
+    __asm__ __volatile__ ("dmb st" : : : "memory");
+}
+#	elif defined(__ARM_HAVE_LDREX_STREX)
+extern inline void android_memory_barrier(void)
+{
+    __asm__ __volatile__ ("mcr p15, 0, %0, c7, c10, 5" : : "r" (0) : "memory");
+}
+extern inline void android_memory_store_barrier(void)
+{
+    android_memory_barrier();
+}
+#	else
+extern inline void android_memory_barrier(void)
+{
+    typedef void (kuser_memory_barrier)(void);
+    (*(kuser_memory_barrier *)0xffff0fa0)();
+}
+extern inline void android_memory_store_barrier(void)
+{
+    android_memory_barrier();
+}
+#	endif
+#else
+#error atomic operations are unsupported
+#endif
+
+#if ANDROID_SMP == 0
+#define ANDROID_MEMBAR_FULL android_compiler_barrier
+#else
+#define ANDROID_MEMBAR_FULL android_memory_barrier
+#endif
+
+#if ANDROID_SMP == 0
+#define ANDROID_MEMBAR_STORE android_compiler_barrier
+#else
+#define ANDROID_MEMBAR_STORE android_memory_store_barrier
+#endif
+
+#endif /* __DISPATCH__ANDROID__MEMBARRIER_SHIMS__INTERNAL */

src/shims/lock.h

@@ -89,8 +89,10 @@ _dispatch_lock_has_failed_trylock(dispatch_lock lock_value)
 
 #elif defined(__linux__)
 #include <linux/futex.h>
-#if !defined(__x86_64__) && !defined(__i386__)
+#if !defined(__x86_64__) && !defined(__i386__) && !defined(__ANDROID__)
 #include <linux/membarrier.h>
+#elif defined(__ANDROID__)
+#include "shims/android_membarrier.h"
 #endif
 #include <unistd.h>
 #include <sys/syscall.h>   /* For SYS_xxx definitions */
@@ -545,6 +547,9 @@ _dispatch_once_xchg_done(dispatch_once_t *pred)
 #if defined(__i386__) || defined(__x86_64__)
 	// On Intel, any load is a load-acquire, so we don't need to be fancy
 	return os_atomic_xchg(pred, DLOCK_ONCE_DONE, release);
+#elif defined(__ANDROID__)
+	ANDROID_MEMBAR_FULL();
+	return os_atomic_xchg(pred, DLOCK_ONCE_DONE, relaxed);
 #elif defined(__linux__)
 	if (unlikely(syscall(__NR_membarrier, MEMBARRIER_CMD_SHARED, 0) < 0)) {
 		DISPATCH_INTERNAL_CRASH(errno, "sys_membarrier not supported");