third_party/WebKit/Source/wtf/Threading.h

   1 /*
   2  * Copyright (C) 2007, 2008, 2010 Apple Inc. All rights reserved.
   3  * Copyright (C) 2007 Justin Haygood (jhaygood@reaktix.com)
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * 1.  Redistributions of source code must retain the above copyright
  10  *     notice, this list of conditions and the following disclaimer.
  11  * 2.  Redistributions in binary form must reproduce the above copyright
  12  *     notice, this list of conditions and the following disclaimer in the
  13  *     documentation and/or other materials provided with the distribution.
  14  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
  15  *     its contributors may be used to endorse or promote products derived
  16  *     from this software without specific prior written permission.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  19  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  20  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  21  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  22  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  23  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  24  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  25  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  28  */
  29
  30 #ifndef Threading_h
  31 #define Threading_h
  32
  33 #include "wtf/Atomics.h"
  34 #include "wtf/TypeTraits.h"
  35 #include "wtf/WTFExport.h"
  36 #include <stdint.h>
  37
  38 // For portability, we do not make use of C++11 thread-safe statics, as supported
  39 // by some toolchains. Make use of double-checked locking to reduce overhead.
  40 #define AtomicallyInitializedStaticReferenceInternal(T, name, initializer, LOCK, UNLOCK) \
  41     /* Init to nullptr is thread-safe on all implementations. */        \
  42     static void* name##Pointer = nullptr;                               \
  43     if (!WTF::acquireLoad(&name##Pointer)) {                            \
  44         LOCK;                                                           \
  45         if (!WTF::acquireLoad(&name##Pointer)) {                        \
  46             WTF::RemoveConst<T>::Type* initializerResult = initializer; \
  47             WTF::releaseStore(&name##Pointer, initializerResult);       \
  48         }                                                               \
  49         UNLOCK;                                                         \
  50     }                                                                   \
  51     T& name = *static_cast<T*>(name##Pointer)
  52
  53 // Uses system-wide default lock. This version cannot be used before
  54 // WTF::initializeThreading() is called.
  55 #define AtomicallyInitializedStaticReference(T, name, initializer)      \
  56     AtomicallyInitializedStaticReferenceInternal(                       \
  57         T, name, initializer, \
  58         WTF::lockAtomicallyInitializedStaticMutex(),                    \
  59         WTF::unlockAtomicallyInitializedStaticMutex())
  60
  61 // Same as above but uses a given lock.
  62 #define AtomicallyInitializedStaticReferenceWithLock(T, name, initializer, lockable)  \
  63     AtomicallyInitializedStaticReferenceInternal(                       \
  64         T, name, initializer, lockable.lock(), lockable.unlock());
  65
  66 namespace WTF {
  67
  68 #if OS(WIN)
  69 typedef uint32_t ThreadIdentifier;
  70 #else
  71 typedef intptr_t ThreadIdentifier;
  72 #endif
  73
  74 WTF_EXPORT ThreadIdentifier currentThread();
  75
  76 WTF_EXPORT void lockAtomicallyInitializedStaticMutex();
  77 WTF_EXPORT void unlockAtomicallyInitializedStaticMutex();
  78
  79 #if ENABLE(ASSERT)
  80 WTF_EXPORT bool isAtomicallyInitializedStaticMutexLockHeld();
  81 WTF_EXPORT bool isBeforeThreadCreated();
  82 WTF_EXPORT void willCreateThread();
  83 #endif
  84
  85 } // namespace WTF
  86
  87 using WTF::ThreadIdentifier;
  88 using WTF::currentThread;
  89
  90 #endif // Threading_h