78 lines
2.9 KiB
C++
78 lines
2.9 KiB
C++
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// Copyright 2012 the V8 project authors. All rights reserved.
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived
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// from this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#include "once.h"
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#ifdef _WIN32
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#include <windows.h>
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#else
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#include <sched.h>
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#endif
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#include "atomicops.h"
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#include "checks.h"
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namespace v8 {
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namespace internal {
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void CallOnceImpl(OnceType* once, PointerArgFunction init_func, void* arg) {
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AtomicWord state = Acquire_Load(once);
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// Fast path. The provided function was already executed.
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if (state == ONCE_STATE_DONE) {
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return;
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}
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// The function execution did not complete yet. The once object can be in one
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// of the two following states:
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// - UNINITIALIZED: We are the first thread calling this function.
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// - EXECUTING_FUNCTION: Another thread is already executing the function.
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//
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// First, try to change the state from UNINITIALIZED to EXECUTING_FUNCTION
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// atomically.
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state = Acquire_CompareAndSwap(
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once, ONCE_STATE_UNINITIALIZED, ONCE_STATE_EXECUTING_FUNCTION);
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if (state == ONCE_STATE_UNINITIALIZED) {
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// We are the first thread to call this function, so we have to call the
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// function.
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init_func(arg);
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Release_Store(once, ONCE_STATE_DONE);
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} else {
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// Another thread has already started executing the function. We need to
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// wait until it completes the initialization.
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while (state == ONCE_STATE_EXECUTING_FUNCTION) {
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#ifdef _WIN32
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::Sleep(0);
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#else
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sched_yield();
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#endif
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state = Acquire_Load(once);
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}
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}
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}
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} } // namespace v8::internal
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