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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2022, Idan Horowitz <idan.horowitz@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/Locking/LockLocation.h>
#include <Kernel/Locking/LockMode.h>
#include <Kernel/WaitQueue.h>
namespace Kernel {
class Mutex {
friend class Thread;
AK_MAKE_NONCOPYABLE(Mutex);
AK_MAKE_NONMOVABLE(Mutex);
public:
using Mode = LockMode;
// FIXME: remove this after annihilating Process::m_big_lock
enum class MutexBehavior {
Regular,
BigLock,
};
Mutex(StringView name = {}, MutexBehavior behavior = MutexBehavior::Regular)
: m_name(name)
, m_behavior(behavior)
{
}
~Mutex() = default;
void lock(Mode mode = Mode::Exclusive, LockLocation const& location = LockLocation::current());
void restore_exclusive_lock(u32, LockLocation const& location = LockLocation::current());
void unlock();
[[nodiscard]] Mode force_unlock_exclusive_if_locked(u32&);
[[nodiscard]] bool is_locked() const
{
SpinlockLocker lock(m_lock);
return m_mode != Mode::Unlocked;
}
[[nodiscard]] bool is_exclusively_locked_by_current_thread() const
{
SpinlockLocker lock(m_lock);
VERIFY(m_mode != Mode::Shared); // This method should only be used on exclusively-held locks
if (m_mode == Mode::Unlocked)
return false;
return m_holder == Thread::current();
}
[[nodiscard]] StringView name() const { return m_name; }
static StringView mode_to_string(Mode mode)
{
switch (mode) {
case Mode::Unlocked:
return "unlocked"sv;
case Mode::Exclusive:
return "exclusive"sv;
case Mode::Shared:
return "shared"sv;
default:
return "invalid"sv;
}
}
private:
using BlockedThreadList = IntrusiveList<&Thread::m_blocked_threads_list_node>;
// FIXME: remove this after annihilating Process::m_big_lock
using BigLockBlockedThreadList = IntrusiveList<&Thread::m_big_lock_blocked_threads_list_node>;
void block(Thread&, Mode, SpinlockLocker<Spinlock>&, u32);
void unblock_waiters(Mode);
StringView m_name;
Mode m_mode { Mode::Unlocked };
// FIXME: remove this after annihilating Process::m_big_lock
MutexBehavior m_behavior;
// 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;
size_t m_shared_holders { 0 };
struct BlockedThreadLists {
BlockedThreadList exclusive;
BlockedThreadList shared;
// FIXME: remove this after annihilating Process::m_big_lock
BigLockBlockedThreadList exclusive_big_lock;
ALWAYS_INLINE BlockedThreadList& list_for_mode(Mode mode)
{
VERIFY(mode == Mode::Exclusive || mode == Mode::Shared);
return mode == Mode::Exclusive ? exclusive : shared;
}
};
SpinlockProtected<BlockedThreadLists> m_blocked_thread_lists;
mutable Spinlock m_lock;
#if LOCK_SHARED_UPGRADE_DEBUG
HashMap<Thread*, u32> m_shared_holders_map;
#endif
};
class MutexLocker {
AK_MAKE_NONCOPYABLE(MutexLocker);
public:
ALWAYS_INLINE explicit MutexLocker()
: m_lock(nullptr)
, m_locked(false)
{
}
ALWAYS_INLINE explicit MutexLocker(Mutex& l, Mutex::Mode mode = Mutex::Mode::Exclusive, LockLocation const& location = LockLocation::current())
: m_lock(&l)
{
m_lock->lock(mode, location);
}
ALWAYS_INLINE ~MutexLocker()
{
if (m_locked)
unlock();
}
ALWAYS_INLINE void unlock()
{
VERIFY(m_lock);
VERIFY(m_locked);
m_locked = false;
m_lock->unlock();
}
ALWAYS_INLINE void attach_and_lock(Mutex& lock, Mutex::Mode mode = Mutex::Mode::Exclusive, LockLocation const& location = LockLocation::current())
{
VERIFY(!m_locked);
m_lock = &lock;
m_locked = true;
m_lock->lock(mode, location);
}
ALWAYS_INLINE void lock(Mutex::Mode mode = Mutex::Mode::Exclusive, LockLocation const& location = LockLocation::current())
{
VERIFY(m_lock);
VERIFY(!m_locked);
m_locked = true;
m_lock->lock(mode, location);
}
private:
Mutex* m_lock;
bool m_locked { true };
};
}
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