mutex
Go to the documentation of this file.
// <mutex> -*- C++ -*-
// Copyright (C) 2003-2015 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/** @file include/mutex
* This is a Standard C++ Library header.
*/
#ifndef _GLIBCXX_MUTEX
#define _GLIBCXX_MUTEX 1
#pragma GCC system_header
#if __cplusplus < 201103L
# include <bits/c++0x_warning.h>
#else
#include <tuple>
#include <chrono>
#include <exception>
#include <type_traits>
#include <functional>
#include <system_error>
#include <bits/functexcept.h>
#include <bits/gthr.h>
#include <bits/move.h> // for std::swap
#include <bits/cxxabi_forced.h>
#ifdef _GLIBCXX_USE_C99_STDINT_TR1
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
#ifdef _GLIBCXX_HAS_GTHREADS
// Common base class for std::mutex and std::timed_mutex
class __mutex_base
{
protected:
typedef __gthread_mutex_t __native_type;
#ifdef __GTHREAD_MUTEX_INIT
__native_type _M_mutex = __GTHREAD_MUTEX_INIT;
constexpr __mutex_base() noexcept = default;
#else
__native_type _M_mutex;
__mutex_base() noexcept
{
// XXX EAGAIN, ENOMEM, EPERM, EBUSY(may), EINVAL(may)
__GTHREAD_MUTEX_INIT_FUNCTION(&_M_mutex);
}
~__mutex_base() noexcept { __gthread_mutex_destroy(&_M_mutex); }
#endif
__mutex_base(const __mutex_base&) = delete;
__mutex_base& operator=(const __mutex_base&) = delete;
};
// Common base class for std::recursive_mutex and std::recursive_timed_mutex
class __recursive_mutex_base
{
protected:
typedef __gthread_recursive_mutex_t __native_type;
__recursive_mutex_base(const __recursive_mutex_base&) = delete;
__recursive_mutex_base& operator=(const __recursive_mutex_base&) = delete;
#ifdef __GTHREAD_RECURSIVE_MUTEX_INIT
__native_type _M_mutex = __GTHREAD_RECURSIVE_MUTEX_INIT;
__recursive_mutex_base() = default;
#else
__native_type _M_mutex;
__recursive_mutex_base()
{
// XXX EAGAIN, ENOMEM, EPERM, EBUSY(may), EINVAL(may)
__GTHREAD_RECURSIVE_MUTEX_INIT_FUNCTION(&_M_mutex);
}
~__recursive_mutex_base()
{ __gthread_recursive_mutex_destroy(&_M_mutex); }
#endif
};
/**
* @defgroup mutexes Mutexes
* @ingroup concurrency
*
* Classes for mutex support.
* @{
*/
/// The standard mutex type.
class mutex : private __mutex_base
{
public:
typedef __native_type* native_handle_type;
#ifdef __GTHREAD_MUTEX_INIT
constexpr
#endif
mutex() noexcept = default;
~mutex() = default;
mutex(const mutex&) = delete;
mutex& operator=(const mutex&) = delete;
void
lock()
{
int __e = __gthread_mutex_lock(&_M_mutex);
// EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
if (__e)
__throw_system_error(__e);
}
bool
try_lock() noexcept
{
// XXX EINVAL, EAGAIN, EBUSY
return !__gthread_mutex_trylock(&_M_mutex);
}
void
unlock()
{
// XXX EINVAL, EAGAIN, EPERM
__gthread_mutex_unlock(&_M_mutex);
}
native_handle_type
native_handle()
{ return &_M_mutex; }
};
/// The standard recursive mutex type.
class recursive_mutex : private __recursive_mutex_base
{
public:
typedef __native_type* native_handle_type;
recursive_mutex() = default;
~recursive_mutex() = default;
recursive_mutex(const recursive_mutex&) = delete;
recursive_mutex& operator=(const recursive_mutex&) = delete;
void
lock()
{
int __e = __gthread_recursive_mutex_lock(&_M_mutex);
// EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
if (__e)
__throw_system_error(__e);
}
bool
try_lock() noexcept
{
// XXX EINVAL, EAGAIN, EBUSY
return !__gthread_recursive_mutex_trylock(&_M_mutex);
}
void
unlock()
{
// XXX EINVAL, EAGAIN, EBUSY
__gthread_recursive_mutex_unlock(&_M_mutex);
}
native_handle_type
native_handle()
{ return &_M_mutex; }
};
#if _GTHREAD_USE_MUTEX_TIMEDLOCK
template<typename _Derived>
class __timed_mutex_impl
{
protected:
typedef chrono::high_resolution_clock __clock_t;
template<typename _Rep, typename _Period>
bool
_M_try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
{
using chrono::steady_clock;
auto __rt = chrono::duration_cast<steady_clock::duration>(__rtime);
if (ratio_greater<steady_clock::period, _Period>())
++__rt;
return _M_try_lock_until(steady_clock::now() + __rt);
}
template<typename _Duration>
bool
_M_try_lock_until(const chrono::time_point<__clock_t,
_Duration>& __atime)
{
auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
__gthread_time_t __ts = {
static_cast<std::time_t>(__s.time_since_epoch().count()),
static_cast<long>(__ns.count())
};
auto __mutex = static_cast<_Derived*>(this)->native_handle();
return !__gthread_mutex_timedlock(__mutex, &__ts);
}
template<typename _Clock, typename _Duration>
bool
_M_try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
{
auto __rtime = __atime - _Clock::now();
return _M_try_lock_until(__clock_t::now() + __rtime);
}
};
/// The standard timed mutex type.
class timed_mutex
: private __mutex_base, public __timed_mutex_impl<timed_mutex>
{
public:
typedef __native_type* native_handle_type;
timed_mutex() = default;
~timed_mutex() = default;
timed_mutex(const timed_mutex&) = delete;
timed_mutex& operator=(const timed_mutex&) = delete;
void
lock()
{
int __e = __gthread_mutex_lock(&_M_mutex);
// EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
if (__e)
__throw_system_error(__e);
}
bool
try_lock() noexcept
{
// XXX EINVAL, EAGAIN, EBUSY
return !__gthread_mutex_trylock(&_M_mutex);
}
template <class _Rep, class _Period>
bool
try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
{ return _M_try_lock_for(__rtime); }
template <class _Clock, class _Duration>
bool
try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
{ return _M_try_lock_until(__atime); }
void
unlock()
{
// XXX EINVAL, EAGAIN, EBUSY
__gthread_mutex_unlock(&_M_mutex);
}
native_handle_type
native_handle()
{ return &_M_mutex; }
};
/// The standard recursive timed mutex type.
class recursive_timed_mutex
: private __recursive_mutex_base,
public __timed_mutex_impl<recursive_timed_mutex>
{
public:
typedef __native_type* native_handle_type;
recursive_timed_mutex() = default;
~recursive_timed_mutex() = default;
recursive_timed_mutex(const recursive_timed_mutex&) = delete;
recursive_timed_mutex& operator=(const recursive_timed_mutex&) = delete;
void
lock()
{
int __e = __gthread_recursive_mutex_lock(&_M_mutex);
// EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
if (__e)
__throw_system_error(__e);
}
bool
try_lock() noexcept
{
// XXX EINVAL, EAGAIN, EBUSY
return !__gthread_recursive_mutex_trylock(&_M_mutex);
}
template <class _Rep, class _Period>
bool
try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
{ return _M_try_lock_for(__rtime); }
template <class _Clock, class _Duration>
bool
try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
{ return _M_try_lock_until(__atime); }
void
unlock()
{
// XXX EINVAL, EAGAIN, EBUSY
__gthread_recursive_mutex_unlock(&_M_mutex);
}
native_handle_type
native_handle()
{ return &_M_mutex; }
};
#endif
#endif // _GLIBCXX_HAS_GTHREADS
/// Do not acquire ownership of the mutex.
struct defer_lock_t { };
/// Try to acquire ownership of the mutex without blocking.
struct try_to_lock_t { };
/// Assume the calling thread has already obtained mutex ownership
/// and manage it.
struct adopt_lock_t { };
/// Tag used to prevent a scoped lock from acquiring ownership of a mutex.
constexpr defer_lock_t defer_lock { };
/// Tag used to prevent a scoped lock from blocking if a mutex is locked.
constexpr try_to_lock_t try_to_lock { };
/// Tag used to make a scoped lock take ownership of a locked mutex.
constexpr adopt_lock_t adopt_lock { };
/** @brief A movable scoped lock type.
*
* A unique_lock controls mutex ownership within a scope. Ownership of the
* mutex can be delayed until after construction and can be transferred
* to another unique_lock by move construction or move assignment. If a
* mutex lock is owned when the destructor runs ownership will be released.
*/
template<typename _Mutex>
class lock_guard
{
public:
typedef _Mutex mutex_type;
explicit lock_guard(mutex_type& __m) : _M_device(__m)
{ _M_device.lock(); }
lock_guard(mutex_type& __m, adopt_lock_t) : _M_device(__m)
{ } // calling thread owns mutex
~lock_guard()
{ _M_device.unlock(); }
lock_guard(const lock_guard&) = delete;
lock_guard& operator=(const lock_guard&) = delete;
private:
mutex_type& _M_device;
};
/// unique_lock
template<typename _Mutex>
class unique_lock
{
public:
typedef _Mutex mutex_type;
unique_lock() noexcept
: _M_device(0), _M_owns(false)
{ }
explicit unique_lock(mutex_type& __m)
: _M_device(std::__addressof(__m)), _M_owns(false)
{
lock();
_M_owns = true;
}
unique_lock(mutex_type& __m, defer_lock_t) noexcept
: _M_device(std::__addressof(__m)), _M_owns(false)
{ }
unique_lock(mutex_type& __m, try_to_lock_t)
: _M_device(std::__addressof(__m)), _M_owns(_M_device->try_lock())
{ }
unique_lock(mutex_type& __m, adopt_lock_t)
: _M_device(std::__addressof(__m)), _M_owns(true)
{
// XXX calling thread owns mutex
}
template<typename _Clock, typename _Duration>
unique_lock(mutex_type& __m,
const chrono::time_point<_Clock, _Duration>& __atime)
: _M_device(std::__addressof(__m)),
_M_owns(_M_device->try_lock_until(__atime))
{ }
template<typename _Rep, typename _Period>
unique_lock(mutex_type& __m,
const chrono::duration<_Rep, _Period>& __rtime)
: _M_device(std::__addressof(__m)),
_M_owns(_M_device->try_lock_for(__rtime))
{ }
~unique_lock()
{
if (_M_owns)
unlock();
}
unique_lock(const unique_lock&) = delete;
unique_lock& operator=(const unique_lock&) = delete;
unique_lock(unique_lock&& __u) noexcept
: _M_device(__u._M_device), _M_owns(__u._M_owns)
{
__u._M_device = 0;
__u._M_owns = false;
}
unique_lock& operator=(unique_lock&& __u) noexcept
{
if(_M_owns)
unlock();
unique_lock(std::move(__u)).swap(*this);
__u._M_device = 0;
__u._M_owns = false;
return *this;
}
void
lock()
{
if (!_M_device)
__throw_system_error(int(errc::operation_not_permitted));
else if (_M_owns)
__throw_system_error(int(errc::resource_deadlock_would_occur));
else
{
_M_device->lock();
_M_owns = true;
}
}
bool
try_lock()
{
if (!_M_device)
__throw_system_error(int(errc::operation_not_permitted));
else if (_M_owns)
__throw_system_error(int(errc::resource_deadlock_would_occur));
else
{
_M_owns = _M_device->try_lock();
return _M_owns;
}
}
template<typename _Clock, typename _Duration>
bool
try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
{
if (!_M_device)
__throw_system_error(int(errc::operation_not_permitted));
else if (_M_owns)
__throw_system_error(int(errc::resource_deadlock_would_occur));
else
{
_M_owns = _M_device->try_lock_until(__atime);
return _M_owns;
}
}
template<typename _Rep, typename _Period>
bool
try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
{
if (!_M_device)
__throw_system_error(int(errc::operation_not_permitted));
else if (_M_owns)
__throw_system_error(int(errc::resource_deadlock_would_occur));
else
{
_M_owns = _M_device->try_lock_for(__rtime);
return _M_owns;
}
}
void
unlock()
{
if (!_M_owns)
__throw_system_error(int(errc::operation_not_permitted));
else if (_M_device)
{
_M_device->unlock();
_M_owns = false;
}
}
void
swap(unique_lock& __u) noexcept
{
std::swap(_M_device, __u._M_device);
std::swap(_M_owns, __u._M_owns);
}
mutex_type*
release() noexcept
{
mutex_type* __ret = _M_device;
_M_device = 0;
_M_owns = false;
return __ret;
}
bool
owns_lock() const noexcept
{ return _M_owns; }
explicit operator bool() const noexcept
{ return owns_lock(); }
mutex_type*
mutex() const noexcept
{ return _M_device; }
private:
mutex_type* _M_device;
bool _M_owns; // XXX use atomic_bool
};
/// Swap overload for unique_lock objects.
template<typename _Mutex>
inline void
swap(unique_lock<_Mutex>& __x, unique_lock<_Mutex>& __y) noexcept
{ __x.swap(__y); }
template<typename _Lock>
inline unique_lock<_Lock>
__try_to_lock(_Lock& __l)
{ return unique_lock<_Lock>{__l, try_to_lock}; }
template<int _Idx, bool _Continue = true>
struct __try_lock_impl
{
template<typename... _Lock>
static void
__do_try_lock(tuple<_Lock&...>& __locks, int& __idx)
{
__idx = _Idx;
auto __lock = std::__try_to_lock(std::get<_Idx>(__locks));
if (__lock.owns_lock())
{
constexpr bool __cont = _Idx + 2 < sizeof...(_Lock);
using __try_locker = __try_lock_impl<_Idx + 1, __cont>;
__try_locker::__do_try_lock(__locks, __idx);
if (__idx == -1)
__lock.release();
}
}
};
template<int _Idx>
struct __try_lock_impl<_Idx, false>
{
template<typename... _Lock>
static void
__do_try_lock(tuple<_Lock&...>& __locks, int& __idx)
{
__idx = _Idx;
auto __lock = std::__try_to_lock(std::get<_Idx>(__locks));
if (__lock.owns_lock())
{
__idx = -1;
__lock.release();
}
}
};
/** @brief Generic try_lock.
* @param __l1 Meets Mutex requirements (try_lock() may throw).
* @param __l2 Meets Mutex requirements (try_lock() may throw).
* @param __l3 Meets Mutex requirements (try_lock() may throw).
* @return Returns -1 if all try_lock() calls return true. Otherwise returns
* a 0-based index corresponding to the argument that returned false.
* @post Either all arguments are locked, or none will be.
*
* Sequentially calls try_lock() on each argument.
*/
template<typename _Lock1, typename _Lock2, typename... _Lock3>
int
try_lock(_Lock1& __l1, _Lock2& __l2, _Lock3&... __l3)
{
int __idx;
auto __locks = std::tie(__l1, __l2, __l3...);
__try_lock_impl<0>::__do_try_lock(__locks, __idx);
return __idx;
}
/** @brief Generic lock.
* @param __l1 Meets Mutex requirements (try_lock() may throw).
* @param __l2 Meets Mutex requirements (try_lock() may throw).
* @param __l3 Meets Mutex requirements (try_lock() may throw).
* @throw An exception thrown by an argument's lock() or try_lock() member.
* @post All arguments are locked.
*
* All arguments are locked via a sequence of calls to lock(), try_lock()
* and unlock(). If the call exits via an exception any locks that were
* obtained will be released.
*/
template<typename _L1, typename _L2, typename... _L3>
void
lock(_L1& __l1, _L2& __l2, _L3&... __l3)
{
while (true)
{
using __try_locker = __try_lock_impl<0, sizeof...(_L3) != 0>;
unique_lock<_L1> __first(__l1);
int __idx;
auto __locks = std::tie(__l2, __l3...);
__try_locker::__do_try_lock(__locks, __idx);
if (__idx == -1)
{
__first.release();
return;
}
}
}
#ifdef _GLIBCXX_HAS_GTHREADS
/// once_flag
struct once_flag
{
private:
typedef __gthread_once_t __native_type;
__native_type _M_once = __GTHREAD_ONCE_INIT;
public:
/// Constructor
constexpr once_flag() noexcept = default;
/// Deleted copy constructor
once_flag(const once_flag&) = delete;
/// Deleted assignment operator
once_flag& operator=(const once_flag&) = delete;
template<typename _Callable, typename... _Args>
friend void
call_once(once_flag& __once, _Callable&& __f, _Args&&... __args);
};
#ifdef _GLIBCXX_HAVE_TLS
extern __thread void* __once_callable;
extern __thread void (*__once_call)();
template<typename _Callable>
inline void
__once_call_impl()
{
(*(_Callable*)__once_callable)();
}
#else
extern function<void()> __once_functor;
extern void
__set_once_functor_lock_ptr(unique_lock<mutex>*);
extern mutex&
__get_once_mutex();
#endif
extern "C" void __once_proxy(void);
/// call_once
template<typename _Callable, typename... _Args>
void
call_once(once_flag& __once, _Callable&& __f, _Args&&... __args)
{
#ifdef _GLIBCXX_HAVE_TLS
auto __bound_functor = std::__bind_simple(std::forward<_Callable>(__f),
std::forward<_Args>(__args)...);
__once_callable = std::__addressof(__bound_functor);
__once_call = &__once_call_impl<decltype(__bound_functor)>;
#else
unique_lock<mutex> __functor_lock(__get_once_mutex());
auto __callable = std::__bind_simple(std::forward<_Callable>(__f),
std::forward<_Args>(__args)...);
__once_functor = [&]() { __callable(); };
__set_once_functor_lock_ptr(&__functor_lock);
#endif
int __e = __gthread_once(&__once._M_once, &__once_proxy);
#ifndef _GLIBCXX_HAVE_TLS
if (__functor_lock)
__set_once_functor_lock_ptr(0);
#endif
if (__e)
__throw_system_error(__e);
}
#endif // _GLIBCXX_HAS_GTHREADS
// @} group mutexes
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#endif // _GLIBCXX_USE_C99_STDINT_TR1
#endif // C++11
#endif // _GLIBCXX_MUTEX