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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  *  * Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  *  * Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in
     12  *    the documentation and/or other materials provided with the
     13  *    distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     16  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     17  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     18  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     19  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     21  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
     22  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     23  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     24  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     25  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 #ifndef _SYS_ATOMICS_H
     29 #define _SYS_ATOMICS_H
     30 
     31 #include <sys/cdefs.h>
     32 #include <sys/time.h>
     33 
     34 __BEGIN_DECLS
     35 
     36 /* Note: atomic operations that were exported by the C library didn't
     37  *       provide any memory barriers, which created potential issues on
     38  *       multi-core devices. We now define them as inlined calls to
     39  *       GCC sync builtins, which always provide a full barrier.
     40  *
     41  *       NOTE: The C library still exports atomic functions by the same
     42  *              name to ensure ABI stability for existing NDK machine code.
     43  *
     44  *       If you are an NDK developer, we encourage you to rebuild your
     45  *       unmodified sources against this header as soon as possible.
     46  */
     47 #define __ATOMIC_INLINE__ static __inline__ __attribute__((always_inline))
     48 
     49 __ATOMIC_INLINE__ int
     50 __atomic_cmpxchg(int old, int _new, volatile int *ptr)
     51 {
     52     /* We must return 0 on success */
     53     return __sync_val_compare_and_swap(ptr, old, _new) != old;
     54 }
     55 
     56 __ATOMIC_INLINE__ int
     57 __atomic_swap(int _new, volatile int *ptr)
     58 {
     59     int prev;
     60     do {
     61         prev = *ptr;
     62     } while (__sync_val_compare_and_swap(ptr, prev, _new) != prev);
     63     return prev;
     64 }
     65 
     66 __ATOMIC_INLINE__ int
     67 __atomic_dec(volatile int *ptr)
     68 {
     69   return __sync_fetch_and_sub (ptr, 1);
     70 }
     71 
     72 __ATOMIC_INLINE__ int
     73 __atomic_inc(volatile int *ptr)
     74 {
     75   return __sync_fetch_and_add (ptr, 1);
     76 }
     77 
     78 
     79 int __futex_wait(volatile void *ftx, int val, const struct timespec *timeout);
     80 int __futex_wake(volatile void *ftx, int count);
     81 
     82 __END_DECLS
     83 
     84 #endif /* _SYS_ATOMICS_H */
     85