| /* |
| * 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); |
| } |