1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 #ifndef BIONIC_ATOMIC_X86_H 17 #define BIONIC_ATOMIC_X86_H 18 19 /* Define a full memory barrier, this is only needed if we build the 20 * platform for a multi-core device. 21 */ 22 __ATOMIC_INLINE__ void __bionic_memory_barrier() { 23 #if defined(ANDROID_SMP) && ANDROID_SMP == 1 24 __asm__ __volatile__ ( "mfence" : : : "memory" ); 25 #else 26 /* A simple compiler barrier. */ 27 __asm__ __volatile__ ( "" : : : "memory" ); 28 #endif 29 } 30 31 /* Compare-and-swap, without any explicit barriers. Note that this function 32 * returns 0 on success, and 1 on failure. The opposite convention is typically 33 * used on other platforms. 34 */ 35 __ATOMIC_INLINE__ int __bionic_cmpxchg(int32_t old_value, int32_t new_value, volatile int32_t* ptr) { 36 int32_t prev; 37 __asm__ __volatile__ ("lock; cmpxchgl %1, %2" 38 : "=a" (prev) 39 : "q" (new_value), "m" (*ptr), "0" (old_value) 40 : "memory"); 41 return prev != old_value; 42 } 43 44 /* Swap, without any explicit barriers. */ 45 __ATOMIC_INLINE__ int32_t __bionic_swap(int32_t new_value, volatile int32_t *ptr) { 46 __asm__ __volatile__ ("xchgl %1, %0" 47 : "=r" (new_value) 48 : "m" (*ptr), "0" (new_value) 49 : "memory"); 50 return new_value; 51 } 52 53 /* Atomic decrement, without explicit barriers. */ 54 __ATOMIC_INLINE__ int32_t __bionic_atomic_dec(volatile int32_t* ptr) { 55 int increment = -1; 56 __asm__ __volatile__ ("lock; xaddl %0, %1" 57 : "+r" (increment), "+m" (*ptr) 58 : : "memory"); 59 /* increment now holds the old value of *ptr */ 60 return increment; 61 } 62 63 #endif /* BIONIC_ATOMIC_X86_H */ 64
