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diff --git a/src/google/protobuf/stubs/once.cc b/src/google/protobuf/stubs/once.cc
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-// Protocol Buffers - Google's data interchange format
-// Copyright 2008 Google Inc. All rights reserved.
-// https://developers.google.com/protocol-buffers/
-//
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted provided that the following conditions are
-// met:
-//
-// * Redistributions of source code must retain the above copyright
-// notice, this list of conditions and the following disclaimer.
-// * Redistributions in binary form must reproduce the above
-// copyright notice, this list of conditions and the following disclaimer
-// in the documentation and/or other materials provided with the
-// distribution.
-// * Neither the name of Google Inc. nor the names of its
-// contributors may be used to endorse or promote products derived from
-// this software without specific prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-// Author: kenton@google.com (Kenton Varda)
-//
-// emulates google3/base/once.h
-//
-// This header is intended to be included only by internal .cc files and
-// generated .pb.cc files. Users should not use this directly.
-
-#include <google/protobuf/stubs/once.h>
-
-#ifndef GOOGLE_PROTOBUF_NO_THREAD_SAFETY
-
-#ifdef _WIN32
-#include <windows.h>
-#else
-#include <sched.h>
-#endif
-
-#include <google/protobuf/stubs/atomicops.h>
-
-namespace google {
-namespace protobuf {
-
-namespace {
-
-void SchedYield() {
-#ifdef _WIN32
- Sleep(0);
-#else // POSIX
- sched_yield();
-#endif
-}
-
-} // namespace
-
-void GoogleOnceInitImpl(ProtobufOnceType* once, Closure* closure) {
- internal::AtomicWord state = internal::Acquire_Load(once);
- // Fast path. The provided closure was already executed.
- if (state == ONCE_STATE_DONE) {
- return;
- }
- // The closure execution did not complete yet. The once object can be in one
- // of the two following states:
- // - UNINITIALIZED: We are the first thread calling this function.
- // - EXECUTING_CLOSURE: Another thread is already executing the closure.
- //
- // First, try to change the state from UNINITIALIZED to EXECUTING_CLOSURE
- // atomically.
- state = internal::Acquire_CompareAndSwap(
- once, ONCE_STATE_UNINITIALIZED, ONCE_STATE_EXECUTING_CLOSURE);
- if (state == ONCE_STATE_UNINITIALIZED) {
- // We are the first thread to call this function, so we have to call the
- // closure.
- closure->Run();
- internal::Release_Store(once, ONCE_STATE_DONE);
- } else {
- // Another thread has already started executing the closure. We need to
- // wait until it completes the initialization.
- while (state == ONCE_STATE_EXECUTING_CLOSURE) {
- // Note that futex() could be used here on Linux as an improvement.
- SchedYield();
- state = internal::Acquire_Load(once);
- }
- }
-}
-
-} // namespace protobuf
-} // namespace google
-
-#endif // GOOGLE_PROTOBUF_NO_THREAD_SAFETY