once.cc revision 3ef787dbeca8a5fb1086949cda830dccee07bfbd
1// Copyright 2012 the V8 project authors. All rights reserved. 2// Redistribution and use in source and binary forms, with or without 3// modification, are permitted provided that the following conditions are 4// met: 5// 6// * Redistributions of source code must retain the above copyright 7// notice, this list of conditions and the following disclaimer. 8// * Redistributions in binary form must reproduce the above 9// copyright notice, this list of conditions and the following 10// disclaimer in the documentation and/or other materials provided 11// with the distribution. 12// * Neither the name of Google Inc. nor the names of its 13// contributors may be used to endorse or promote products derived 14// from this software without specific prior written permission. 15// 16// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 28#include "once.h" 29 30#ifdef _WIN32 31#include <windows.h> 32#else 33#include <sched.h> 34#endif 35 36#include "atomicops.h" 37#include "checks.h" 38 39namespace v8 { 40namespace internal { 41 42void CallOnceImpl(OnceType* once, PointerArgFunction init_func, void* arg) { 43 AtomicWord state = Acquire_Load(once); 44 // Fast path. The provided function was already executed. 45 if (state == ONCE_STATE_DONE) { 46 return; 47 } 48 49 // The function execution did not complete yet. The once object can be in one 50 // of the two following states: 51 // - UNINITIALIZED: We are the first thread calling this function. 52 // - EXECUTING_FUNCTION: Another thread is already executing the function. 53 // 54 // First, try to change the state from UNINITIALIZED to EXECUTING_FUNCTION 55 // atomically. 56 state = Acquire_CompareAndSwap( 57 once, ONCE_STATE_UNINITIALIZED, ONCE_STATE_EXECUTING_FUNCTION); 58 if (state == ONCE_STATE_UNINITIALIZED) { 59 // We are the first thread to call this function, so we have to call the 60 // function. 61 init_func(arg); 62 Release_Store(once, ONCE_STATE_DONE); 63 } else { 64 // Another thread has already started executing the function. We need to 65 // wait until it completes the initialization. 66 while (state == ONCE_STATE_EXECUTING_FUNCTION) { 67#ifdef _WIN32 68 ::Sleep(0); 69#else 70 sched_yield(); 71#endif 72 state = Acquire_Load(once); 73 } 74 } 75} 76 77} } // namespace v8::internal 78