1 files changed, 87 insertions, 0 deletions
diff --git a/libc/arch-arm/bionic/atomics_arm.c b/libc/arch-arm/bionic/atomics_arm.c
new file mode 100644
index 0000000..d69eaff
--- /dev/null
+++ b/libc/arch-arm/bionic/atomics_arm.c
@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+
+/* The purpose of this file is to export a small set of atomic-related
+ * functions from the C library, to ensure binary ABI compatibility for
+ * the NDK.
+ *
+ * These functions were initially exposed by the NDK through <sys/atomics.h>,
+ * which was unfortunate because their implementation didn't provide any
+ * memory barriers at all.
+ *
+ * This wasn't a problem for the platform code that used them, because it
+ * used explicit barrier instructions around them. On the other hand, it means
+ * that any NDK-generated machine code that linked against them would not
+ * perform correctly when running on multi-core devices.
+ *
+ * To fix this, the platform code was first modified to not use any of these
+ * functions (everything is now inlined through assembly statements, see
+ * libc/private/bionic_arm_inline.h and the headers it includes.
+ *
+ * The functions here are thus only for the benefit of NDK applications,
+ * and now includes full memory barriers to prevent any random memory ordering
+ * issue from cropping.
+ *
+ * Note that we also provide an updated <sys/atomics.h> header that defines
+ * always_inlined versions of the functions that use the GCC builtin
+ * intrinsics to perform the same thing.
+ *
+ * NOTE: There is no need for a similar file for non-ARM platforms.
+ */
+
+/* DO NOT INCLUDE <sys/atomics.h> HERE ! */
+
+int
+__atomic_cmpxchg(int old, int _new, volatile int *ptr)
+{
+    /* We must return 0 on success */
+    return __sync_val_compare_and_swap(ptr, old, _new) != old;
+}
+
+int
+__atomic_swap(int _new, volatile int *ptr)
+{
+    int prev;
+    do {
+        prev = *ptr;
+    } while (__sync_val_compare_and_swap(ptr, prev, _new) != prev);
+    return prev;
+}
+
+int
+__atomic_dec(volatile int *ptr)
+{
+  return __sync_fetch_and_sub (ptr, 1);
+}
+
+int
+__atomic_inc(volatile int *ptr)
+{
+  return __sync_fetch_and_add (ptr, 1);
+}