third_party/WebKit/Source/wtf/ThreadIdentifierDataPthreads.h

/*
 * Copyright (C) 2009 Google Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
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 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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#ifndef ThreadIdentifierDataPthreads_h
#define ThreadIdentifierDataPthreads_h

#include "wtf/Noncopyable.h"
#include "wtf/Threading.h"
#include <pthread.h>

namespace WTF {

// Holds ThreadIdentifier in the thread-specific storage and employs pthreads-specific 2-pass destruction to reliably remove
// ThreadIdentifier from threadMap. It assumes regular ThreadSpecific types don't use multiple-pass destruction.
class ThreadIdentifierData {
    WTF_MAKE_NONCOPYABLE(ThreadIdentifierData);
public:
    ~ThreadIdentifierData();

    // One time initialization for this class as a whole.
    // This method must be called before initialize() and it is not thread-safe.
    static void initializeOnce();

    // Creates and puts an instance of ThreadIdentifierData into thread-specific storage.
    static void initialize(ThreadIdentifier identifier);

    // Returns 0 if thread-specific storage was not initialized.
    static ThreadIdentifier identifier();

private:
    ThreadIdentifierData(ThreadIdentifier identifier)
        : m_identifier(identifier)
        , m_isDestroyedOnce(false)
    {
    }

    // This thread-specific destructor is called 2 times when thread terminates:
    // - first, when all the other thread-specific destructors are called, it simply remembers it was 'destroyed once'
    // and re-sets itself into the thread-specific slot to make Pthreads to call it again later.
    // - second, after all thread-specific destructors were invoked, it gets called again - this time, we remove the
    // ThreadIdentifier from the threadMap, completing the cleanup.
    static void destruct(void* data);

    ThreadIdentifier m_identifier;
    bool m_isDestroyedOnce;
    static pthread_key_t m_key;
};

} // namespace WTF

#endif // ThreadIdentifierDataPthreads_h