/* * 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 , * 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 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 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); }