1 /* 2 * Copyright (C) 2013 Google Inc. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions are 6 * met: 7 * 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 11 * copyright notice, this list of conditions and the following disclaimer 12 * in the documentation and/or other materials provided with the 13 * distribution. 14 * * Neither the name of Google Inc. nor the names of its 15 * contributors may be used to endorse or promote products derived from 16 * this software without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29 */ 30 31 #ifndef WTF_SpinLock_h 32 #define WTF_SpinLock_h 33 34 // DESCRIPTION 35 // spinLockLock() and spinLockUnlock() are simple spinlock primitives based on 36 // the standard CPU primitive of atomic increment and decrement of an int at 37 // a given memory address. 38 39 #include "wtf/Atomics.h" 40 41 namespace WTF { 42 43 ALWAYS_INLINE void spinLockLock(int volatile* lock) 44 { 45 while (UNLIKELY(atomicTestAndSetToOne(lock))) { 46 while (*lock) { } // Spin without spamming locked instructions. 47 } 48 } 49 50 ALWAYS_INLINE void spinLockUnlock(int volatile* lock) 51 { 52 atomicSetOneToZero(lock); 53 } 54 55 } // namespace WTF 56 57 using WTF::spinLockLock; 58 using WTF::spinLockUnlock; 59 60 #endif // WTF_SpinLock_h 61
