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94647fa4ab
Instead of using a separate synchronization variable, just use the lock holder TID for synchronization. This way, we only need to CAS when first acquiring a lock.
133 lines
3.1 KiB
C++
133 lines
3.1 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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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 met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (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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*/
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#pragma once
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#ifdef __serenity__
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#include <AK/Assertions.h>
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#include <AK/Types.h>
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#include <AK/Atomic.h>
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#include <unistd.h>
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namespace LibThread {
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class Lock {
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public:
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Lock() {}
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~Lock() {}
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void lock();
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void unlock();
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private:
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Atomic<int> m_holder { 0 };
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u32 m_level { 0 };
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};
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class Locker {
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public:
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[[gnu::always_inline]] inline explicit Locker(Lock& l)
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: m_lock(l)
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{
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lock();
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}
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[[gnu::always_inline]] inline ~Locker() { unlock(); }
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[[gnu::always_inline]] inline void unlock() { m_lock.unlock(); }
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[[gnu::always_inline]] inline void lock() { m_lock.lock(); }
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private:
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Lock& m_lock;
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};
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[[gnu::always_inline]] inline void Lock::lock()
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{
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int tid = gettid();
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if (m_holder == tid) {
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++m_level;
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return;
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}
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for (;;) {
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int expected = 0;
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if (m_holder.compare_exchange_strong(expected, tid, AK::memory_order_acq_rel)) {
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m_holder = tid;
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m_level = 1;
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return;
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}
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donate(m_holder);
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}
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}
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inline void Lock::unlock()
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{
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ASSERT(m_holder == gettid());
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ASSERT(m_level);
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--m_level;
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if (!m_level)
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m_holder.store(0, AK::memory_order_release);
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}
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#define LOCKER(lock) LibThread::Locker locker(lock)
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template<typename T>
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class Lockable {
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public:
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Lockable() {}
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Lockable(T&& resource)
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: m_resource(move(resource))
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{
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}
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Lock& lock() { return m_lock; }
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T& resource() { return m_resource; }
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T lock_and_copy()
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{
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LOCKER(m_lock);
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return m_resource;
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}
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private:
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T m_resource;
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Lock m_lock;
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};
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}
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#else
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namespace LibThread {
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class Lock {
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public:
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Lock() { }
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~Lock() { }
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};
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}
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#define LOCKER(x)
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#endif
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