f1a39dce60
The function must be named __atomic_cmpxchg, not __android_cmpxchg. This typo broke existing prebuilt binaries (they couldn't be loaded at runtime anymore). Change-Id: I25ca7d18329817f0056e616a0409113269ad7b1f
87 lines
3.2 KiB
C
87 lines
3.2 KiB
C
/*
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* Copyright (C) 2011 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/* The purpose of this file is to export a small set of atomic-related
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* functions from the C library, to ensure binary ABI compatibility for
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* the NDK.
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*
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* These functions were initially exposed by the NDK through <sys/atomics.h>,
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* which was unfortunate because their implementation didn't provide any
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* memory barriers at all.
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*
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* This wasn't a problem for the platform code that used them, because it
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* used explicit barrier instructions around them. On the other hand, it means
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* that any NDK-generated machine code that linked against them would not
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* perform correctly when running on multi-core devices.
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*
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* To fix this, the platform code was first modified to not use any of these
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* functions (everything is now inlined through assembly statements, see
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* libc/private/bionic_arm_inline.h and the headers it includes.
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*
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* The functions here are thus only for the benefit of NDK applications,
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* and now includes full memory barriers to prevent any random memory ordering
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* issue from cropping.
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*
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* Note that we also provide an updated <sys/atomics.h> header that defines
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* always_inlined versions of the functions that use the GCC builtin
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* intrinsics to perform the same thing.
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*
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* NOTE: There is no need for a similar file for non-ARM platforms.
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*/
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/* DO NOT INCLUDE <sys/atomics.h> HERE ! */
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int
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__atomic_cmpxchg(int old, int _new, volatile int *ptr)
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{
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/* We must return 0 on success */
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return __sync_val_compare_and_swap(ptr, old, _new) != old;
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}
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int
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__atomic_swap(int _new, volatile int *ptr)
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{
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int prev;
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do {
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prev = *ptr;
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} while (__sync_val_compare_and_swap(ptr, prev, _new) != prev);
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return prev;
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}
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int
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__atomic_dec(volatile int *ptr)
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{
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return __sync_fetch_and_sub (ptr, 1);
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}
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int
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__atomic_inc(volatile int *ptr)
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{
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return __sync_fetch_and_add (ptr, 1);
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}
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