1 // Copyright 2012 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 #include "src/base/once.h"
13 #include "src/base/atomicops.h"
18 void CallOnceImpl(OnceType* once, PointerArgFunction init_func, void* arg) {
19 AtomicWord state = Acquire_Load(once);
20 // Fast path. The provided function was already executed.
21 if (state == ONCE_STATE_DONE) {
25 // The function execution did not complete yet. The once object can be in one
26 // of the two following states:
27 // - UNINITIALIZED: We are the first thread calling this function.
28 // - EXECUTING_FUNCTION: Another thread is already executing the function.
30 // First, try to change the state from UNINITIALIZED to EXECUTING_FUNCTION
32 state = Acquire_CompareAndSwap(
33 once, ONCE_STATE_UNINITIALIZED, ONCE_STATE_EXECUTING_FUNCTION);
34 if (state == ONCE_STATE_UNINITIALIZED) {
35 // We are the first thread to call this function, so we have to call the
38 Release_Store(once, ONCE_STATE_DONE);
40 // Another thread has already started executing the function. We need to
41 // wait until it completes the initialization.
42 while (state == ONCE_STATE_EXECUTING_FUNCTION) {
48 state = Acquire_Load(once);
53 } } // namespace v8::base