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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Assertions.h>
#include <AK/Atomic.h>
#include <AK/HashMap.h>
#include <AK/Types.h>
#include <Kernel/Forward.h>
#include <Kernel/LockMode.h>
#include <Kernel/WaitQueue.h>
namespace Kernel {
class Lock {
AK_MAKE_NONCOPYABLE(Lock);
AK_MAKE_NONMOVABLE(Lock);
public:
using Mode = LockMode;
Lock(const char* name = nullptr)
: m_name(name)
{
}
~Lock() = default;
#if LOCK_DEBUG
void lock(Mode mode = Mode::Exclusive, const SourceLocation& location = SourceLocation::current());
void restore_lock(Mode, u32, const SourceLocation& location = SourceLocation::current());
#else
void lock(Mode = Mode::Exclusive);
void restore_lock(Mode, u32);
#endif
void unlock();
[[nodiscard]] Mode force_unlock_if_locked(u32&);
[[nodiscard]] bool is_locked() const { return m_mode != Mode::Unlocked; }
void clear_waiters();
[[nodiscard]] const char* name() const { return m_name; }
static const char* mode_to_string(Mode mode)
{
switch (mode) {
case Mode::Unlocked:
return "unlocked";
case Mode::Exclusive:
return "exclusive";
case Mode::Shared:
return "shared";
default:
return "invalid";
}
}
private:
Atomic<bool> m_lock { false };
const char* m_name { nullptr };
WaitQueue m_queue;
Atomic<Mode, AK::MemoryOrder::memory_order_relaxed> 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.
RefPtr<Thread> m_holder;
HashMap<Thread*, u32> m_shared_holders;
};
class Locker {
public:
#if LOCK_DEBUG
ALWAYS_INLINE explicit Locker(Lock& l, Lock::Mode mode = Lock::Mode::Exclusive, const SourceLocation& location = SourceLocation::current())
#else
ALWAYS_INLINE explicit Locker(Lock& l, Lock::Mode mode = Lock::Mode::Exclusive)
#endif
: m_lock(l)
{
#if LOCK_DEBUG
m_lock.lock(mode, location);
#else
m_lock.lock(mode);
#endif
}
ALWAYS_INLINE ~Locker()
{
if (m_locked)
unlock();
}
ALWAYS_INLINE void unlock()
{
VERIFY(m_locked);
m_locked = false;
m_lock.unlock();
}
#if LOCK_DEBUG
ALWAYS_INLINE void lock(Lock::Mode mode = Lock::Mode::Exclusive, const SourceLocation& location = SourceLocation::current())
#else
ALWAYS_INLINE void lock(Lock::Mode mode = Lock::Mode::Exclusive)
#endif
{
VERIFY(!m_locked);
m_locked = true;
#if LOCK_DEBUG
m_lock.lock(mode, location);
#else
m_lock.lock(mode);
#endif
}
Lock& get_lock() { return m_lock; }
const Lock& get_lock() const { return m_lock; }
private:
Lock& m_lock;
bool m_locked { true };
};
template<typename T>
class Lockable {
public:
Lockable() = default;
Lockable(T&& resource)
: m_resource(move(resource))
{
}
[[nodiscard]] Lock& lock() { return m_lock; }
[[nodiscard]] T& resource() { return m_resource; }
[[nodiscard]] T lock_and_copy()
{
Locker locker(m_lock);
return m_resource;
}
private:
T m_resource;
Lock m_lock;
};
class ScopedLockRelease {
AK_MAKE_NONCOPYABLE(ScopedLockRelease);
public:
ScopedLockRelease& operator=(ScopedLockRelease&&) = delete;
ScopedLockRelease(Lock& lock)
: m_lock(&lock)
, m_previous_mode(lock.force_unlock_if_locked(m_previous_recursions))
{
}
ScopedLockRelease(ScopedLockRelease&& from)
: m_lock(exchange(from.m_lock, nullptr))
, m_previous_mode(exchange(from.m_previous_mode, Lock::Mode::Unlocked))
, m_previous_recursions(exchange(from.m_previous_recursions, 0))
{
}
~ScopedLockRelease()
{
if (m_lock && m_previous_mode != Lock::Mode::Unlocked)
m_lock->restore_lock(m_previous_mode, m_previous_recursions);
}
void restore_lock()
{
VERIFY(m_lock);
if (m_previous_mode != Lock::Mode::Unlocked) {
m_lock->restore_lock(m_previous_mode, m_previous_recursions);
m_previous_mode = Lock::Mode::Unlocked;
m_previous_recursions = 0;
}
}
void do_not_restore()
{
VERIFY(m_lock);
m_previous_mode = Lock::Mode::Unlocked;
m_previous_recursions = 0;
}
private:
Lock* m_lock;
Lock::Mode m_previous_mode;
u32 m_previous_recursions;
};
}
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