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construct/include/ircd/ctx/mutex.h

172 lines
2.6 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;
template<class queue> void release_sequence(queue &);
}
//
// The mutex only allows one context to lock it and continue,
// additional contexts are queued. This can be used with std::
// locking concepts.
//
class ircd::ctx::mutex
{
bool m;
list q;
public:
bool locked() const;
size_t waiting() const;
bool try_lock();
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();
mutex(mutex &&) noexcept;
mutex(const mutex &) = delete;
mutex &operator=(mutex &&) noexcept;
mutex &operator=(const mutex &) = delete;
~mutex() noexcept;
};
inline
ircd::ctx::mutex::mutex()
:m{false}
{
}
inline
ircd::ctx::mutex::mutex(mutex &&o)
noexcept
:m{std::move(o.m)}
{
o.m = false;
}
inline
ircd::ctx::mutex &
ircd::ctx::mutex::operator=(mutex &&o)
noexcept
{
this->~mutex();
std::swap(m, o.m);
return *this;
}
inline
ircd::ctx::mutex::~mutex()
noexcept
{
assert(!m);
}
inline void
ircd::ctx::mutex::unlock()
{
assert(m);
m = false;
release_sequence(q);
}
inline void
ircd::ctx::mutex::lock()
{
if(likely(try_lock()))
return;
assert(current);
q.push_back(current);
while(!try_lock())
wait();
}
template<class duration>
bool
ircd::ctx::mutex::try_lock_for(const duration &d)
{
return try_lock_until(steady_clock::now() + d);
}
template<class time_point>
bool
ircd::ctx::mutex::try_lock_until(const time_point &tp)
{
if(likely(try_lock()))
return true;
assert(current);
q.push_back(current);
while(!try_lock())
{
if(unlikely(wait_until<std::nothrow_t>(tp)))
{
q.remove(current);
return false;
}
}
return true;
}
inline bool
ircd::ctx::mutex::try_lock()
{
if(m)
return false;
m = true;
return true;
}
inline size_t
ircd::ctx::mutex::waiting()
const
{
return q.size();
}
inline bool
ircd::ctx::mutex::locked()
const
{
return m;
}
template<class queue>
void
ircd::ctx::release_sequence(queue &q)
{
assert(current);
ctx *next; do
{
if(!q.empty())
{
next = q.front();
q.pop_front();
}
else next = nullptr;
}
while(next == current);
if(next)
yield(*next);
}