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construct/include/ircd/ctx/mutex.h

177 lines
2.8 KiB
C++

// Matrix Construct
//
// Copyright (C) Matrix Construct Developers, Authors & Contributors
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice is present in all copies. The
// full license for this software is available in the LICENSE file.
#pragma once
#define HAVE_IRCD_CTX_MUTEX_H
namespace ircd::ctx
{
class mutex;
}
//
// The mutex only allows one context to lock it and continue,
// additional contexts are queued. This can be used with std::
// locking concepts.
//
struct ircd::ctx::mutex
{
dock q;
ctx *m;
void deadlock_assertion() const noexcept;
public:
bool locked() const noexcept;
size_t waiting() const noexcept;
bool waiting(const ctx &) const noexcept;
bool try_lock() noexcept;
template<class time_point> bool try_lock_until(const time_point &);
template<class duration> bool try_lock_for(const duration &);
void lock();
void unlock();
mutex() noexcept;
mutex(mutex &&) noexcept;
mutex(const mutex &) = delete;
mutex &operator=(mutex &&) noexcept;
mutex &operator=(const mutex &) = delete;
~mutex() noexcept;
};
inline
ircd::ctx::mutex::mutex()
noexcept
:m{nullptr}
{
}
inline
ircd::ctx::mutex::mutex(mutex &&o)
noexcept
:q{std::move(o.q)}
,m{std::move(o.m)}
{
o.m = nullptr;
}
inline
ircd::ctx::mutex &
ircd::ctx::mutex::operator=(mutex &&o)
noexcept
{
this->~mutex();
q = std::move(o.q);
m = std::move(o.m);
o.m = nullptr;
return *this;
}
inline
ircd::ctx::mutex::~mutex()
noexcept
{
assert(!m);
}
inline void
ircd::ctx::mutex::unlock()
{
assert(m == current);
m = nullptr;
q.notify_one();
}
inline void
ircd::ctx::mutex::lock()
{
assert(current);
deadlock_assertion();
q.wait([this]
{
return !locked();
});
m = current;
}
template<class duration>
bool
ircd::ctx::mutex::try_lock_for(const duration &d)
{
return try_lock_until(system_clock::now() + d);
}
template<class time_point>
bool
ircd::ctx::mutex::try_lock_until(const time_point &tp)
{
assert(current);
deadlock_assertion();
const bool success
{
q.wait_until(tp, [this]
{
return !locked();
})
};
if(likely(success))
m = current;
return success;
}
inline bool
ircd::ctx::mutex::try_lock()
noexcept
{
assert(current);
deadlock_assertion();
if(locked())
return false;
m = current;
return true;
}
inline bool
ircd::ctx::mutex::waiting(const ctx &c)
const noexcept
{
return q.waiting(c);
}
inline size_t
ircd::ctx::mutex::waiting()
const noexcept
{
return q.size();
}
inline bool
ircd::ctx::mutex::locked()
const noexcept
{
return m;
}
inline void
__attribute__((always_inline, artificial))
ircd::ctx::mutex::deadlock_assertion()
const noexcept
{
assert(!locked() || m != current);
}