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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. 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.
*
* 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 HOLDER 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.
*/
#pragma once
#include <AK/Assertions.h>
#include <AK/Atomic.h>
#include <AK/Types.h>
#include <Kernel/Arch/i386/CPU.h>
#include <Kernel/Forward.h>
#include <Kernel/WaitQueue.h>
namespace Kernel {
class Lock {
public:
Lock(const char* name = nullptr)
: m_name(name)
{
}
~Lock() { }
enum class Mode {
Unlocked,
Shared,
Exclusive
};
void lock(Mode = Mode::Exclusive);
void unlock();
bool force_unlock_if_locked();
bool is_locked() const { return m_holder; }
void clear_waiters();
const char* name() const { return m_name; }
private:
Atomic<bool> m_lock { false };
const char* m_name { nullptr };
WaitQueue m_queue;
Mode m_mode { Mode::Unlocked };
// When locked exclusively, only the thread already holding the lock can
// lock it again. When locked in shared mode, any thread can do that.
u32 m_times_locked { 0 };
// One of the threads that hold this lock, or nullptr. When locked in shared
// mode, this is stored on best effort basis: nullptr value does *not* mean
// the lock is unlocked, it just means we don't know which threads hold it.
// When locked exclusively, this is always the one thread that holds the
// lock.
Thread* m_holder { nullptr };
};
class Locker {
public:
ALWAYS_INLINE explicit Locker(Lock& l, Lock::Mode mode = Lock::Mode::Exclusive)
: m_lock(l)
{
m_lock.lock(mode);
}
ALWAYS_INLINE ~Locker() { unlock(); }
ALWAYS_INLINE void unlock() { m_lock.unlock(); }
ALWAYS_INLINE void lock(Lock::Mode mode = Lock::Mode::Exclusive) { m_lock.lock(mode); }
private:
Lock& m_lock;
};
#define LOCKER(...) Locker locker(__VA_ARGS__)
template<typename T>
class Lockable {
public:
Lockable() { }
Lockable(T&& resource)
: m_resource(move(resource))
{
}
Lock& lock() { return m_lock; }
T& resource() { return m_resource; }
T lock_and_copy()
{
LOCKER(m_lock);
return m_resource;
}
private:
T m_resource;
Lock m_lock;
};
}
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