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https://github.com/RGBCube/serenity
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3d6e08156d
MutexProtected mirrors the identically-named Kernel primitive and can be used to synchronize access to any object that might not be thread safe on its own. Synchronization is done with a simple mutex, so access to a MutexProtected object is potentially blocking. Mutex now has an internal nesting variable which is there to harden it against lock-unlock ordering issues (e.g. double unlocking).
89 lines
1.9 KiB
C++
89 lines
1.9 KiB
C++
/*
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* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
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* Copyright (c) 2021, kleines Filmröllchen <malu.bertsch@gmail.com>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Assertions.h>
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#include <AK/Format.h>
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#include <AK/Noncopyable.h>
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#include <AK/Types.h>
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#include <pthread.h>
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namespace Threading {
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class Mutex {
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AK_MAKE_NONCOPYABLE(Mutex);
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AK_MAKE_NONMOVABLE(Mutex);
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friend class ConditionVariable;
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public:
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Mutex()
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: m_lock_count(0)
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{
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#ifndef __serenity__
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pthread_mutexattr_t attr;
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pthread_mutexattr_init(&attr);
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pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
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pthread_mutex_init(&m_mutex, &attr);
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#endif
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}
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~Mutex()
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{
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VERIFY(m_lock_count == 0);
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// FIXME: pthread_mutex_destroy() is not implemented.
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}
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void lock();
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void unlock();
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private:
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#ifdef __serenity__
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pthread_mutex_t m_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
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#else
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pthread_mutex_t m_mutex;
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#endif
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unsigned m_lock_count { 0 };
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};
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class MutexLocker {
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AK_MAKE_NONCOPYABLE(MutexLocker);
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AK_MAKE_NONMOVABLE(MutexLocker);
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public:
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ALWAYS_INLINE explicit MutexLocker(Mutex& mutex)
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: m_mutex(mutex)
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{
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lock();
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}
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ALWAYS_INLINE ~MutexLocker()
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{
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unlock();
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}
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ALWAYS_INLINE void unlock() { m_mutex.unlock(); }
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ALWAYS_INLINE void lock() { m_mutex.lock(); }
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private:
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Mutex& m_mutex;
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};
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ALWAYS_INLINE void Mutex::lock()
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{
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pthread_mutex_lock(&m_mutex);
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m_lock_count++;
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}
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ALWAYS_INLINE void Mutex::unlock()
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{
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VERIFY(m_lock_count > 0);
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// FIXME: We need to protect the lock count with the mutex itself.
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// This may be bad because we're not *technically* unlocked yet,
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// but we're not handling any errors from pthread_mutex_unlock anyways.
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m_lock_count--;
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pthread_mutex_unlock(&m_mutex);
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}
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}
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