// <shared_mutex> -*- C++ -*-
-// Copyright (C) 2013-2016 Free Software Foundation, Inc.
+// Copyright (C) 2013-2024 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
#pragma GCC system_header
-#if __cplusplus <= 201103L
-# include <bits/c++14_warning.h>
-#else
+#include <bits/requires_hosted.h> // concurrency
+
+#if __cplusplus >= 201402L
-#include <bits/c++config.h>
-#include <condition_variable>
+#include <bits/chrono.h>
+#include <bits/error_constants.h>
#include <bits/functexcept.h>
+#include <bits/move.h> // move, __exchange
+#include <bits/std_mutex.h> // defer_lock_t
+
+#define __glibcxx_want_shared_mutex
+#define __glibcxx_want_shared_timed_mutex
+#include <bits/version.h>
+
+#if ! (_GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK)
+# include <condition_variable>
+#endif
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
/**
- * @ingroup mutexes
+ * @addtogroup mutexes
* @{
*/
-#ifdef _GLIBCXX_USE_C99_STDINT_TR1
#ifdef _GLIBCXX_HAS_GTHREADS
-#if __cplusplus > 201402L
-// TODO: #define __cpp_lib_shared_mutex 201505
+#ifdef __cpp_lib_shared_mutex // C++ >= 17 && hosted && gthread
class shared_mutex;
#endif
-#define __cpp_lib_shared_timed_mutex 201402
class shared_timed_mutex;
+ /// @cond undocumented
+
#if _GLIBCXX_USE_PTHREAD_RWLOCK_T
+#ifdef __gthrw
+#define _GLIBCXX_GTHRW(name) \
+ __gthrw(pthread_ ## name); \
+ static inline int \
+ __glibcxx_ ## name (pthread_rwlock_t *__rwlock) \
+ { \
+ if (__gthread_active_p ()) \
+ return __gthrw_(pthread_ ## name) (__rwlock); \
+ else \
+ return 0; \
+ }
+ _GLIBCXX_GTHRW(rwlock_rdlock)
+ _GLIBCXX_GTHRW(rwlock_tryrdlock)
+ _GLIBCXX_GTHRW(rwlock_wrlock)
+ _GLIBCXX_GTHRW(rwlock_trywrlock)
+ _GLIBCXX_GTHRW(rwlock_unlock)
+# ifndef PTHREAD_RWLOCK_INITIALIZER
+ _GLIBCXX_GTHRW(rwlock_destroy)
+ __gthrw(pthread_rwlock_init);
+ static inline int
+ __glibcxx_rwlock_init (pthread_rwlock_t *__rwlock)
+ {
+ if (__gthread_active_p ())
+ return __gthrw_(pthread_rwlock_init) (__rwlock, NULL);
+ else
+ return 0;
+ }
+# endif
+# if _GTHREAD_USE_MUTEX_TIMEDLOCK
+ __gthrw(pthread_rwlock_timedrdlock);
+ static inline int
+ __glibcxx_rwlock_timedrdlock (pthread_rwlock_t *__rwlock,
+ const timespec *__ts)
+ {
+ if (__gthread_active_p ())
+ return __gthrw_(pthread_rwlock_timedrdlock) (__rwlock, __ts);
+ else
+ return 0;
+ }
+ __gthrw(pthread_rwlock_timedwrlock);
+ static inline int
+ __glibcxx_rwlock_timedwrlock (pthread_rwlock_t *__rwlock,
+ const timespec *__ts)
+ {
+ if (__gthread_active_p ())
+ return __gthrw_(pthread_rwlock_timedwrlock) (__rwlock, __ts);
+ else
+ return 0;
+ }
+# endif
+#else
+ static inline int
+ __glibcxx_rwlock_rdlock (pthread_rwlock_t *__rwlock)
+ { return pthread_rwlock_rdlock (__rwlock); }
+ static inline int
+ __glibcxx_rwlock_tryrdlock (pthread_rwlock_t *__rwlock)
+ { return pthread_rwlock_tryrdlock (__rwlock); }
+ static inline int
+ __glibcxx_rwlock_wrlock (pthread_rwlock_t *__rwlock)
+ { return pthread_rwlock_wrlock (__rwlock); }
+ static inline int
+ __glibcxx_rwlock_trywrlock (pthread_rwlock_t *__rwlock)
+ { return pthread_rwlock_trywrlock (__rwlock); }
+ static inline int
+ __glibcxx_rwlock_unlock (pthread_rwlock_t *__rwlock)
+ { return pthread_rwlock_unlock (__rwlock); }
+ static inline int
+ __glibcxx_rwlock_destroy(pthread_rwlock_t *__rwlock)
+ { return pthread_rwlock_destroy (__rwlock); }
+ static inline int
+ __glibcxx_rwlock_init(pthread_rwlock_t *__rwlock)
+ { return pthread_rwlock_init (__rwlock, NULL); }
+# if _GTHREAD_USE_MUTEX_TIMEDLOCK
+ static inline int
+ __glibcxx_rwlock_timedrdlock (pthread_rwlock_t *__rwlock,
+ const timespec *__ts)
+ { return pthread_rwlock_timedrdlock (__rwlock, __ts); }
+ static inline int
+ __glibcxx_rwlock_timedwrlock (pthread_rwlock_t *__rwlock,
+ const timespec *__ts)
+ { return pthread_rwlock_timedwrlock (__rwlock, __ts); }
+# endif
+#endif
+
/// A shared mutex type implemented using pthread_rwlock_t.
class __shared_mutex_pthread
{
public:
__shared_mutex_pthread()
{
- int __ret = pthread_rwlock_init(&_M_rwlock, NULL);
+ int __ret = __glibcxx_rwlock_init(&_M_rwlock);
if (__ret == ENOMEM)
__throw_bad_alloc();
else if (__ret == EAGAIN)
~__shared_mutex_pthread()
{
- int __ret __attribute((__unused__)) = pthread_rwlock_destroy(&_M_rwlock);
+ int __ret __attribute((__unused__)) = __glibcxx_rwlock_destroy(&_M_rwlock);
// Errors not handled: EBUSY, EINVAL
__glibcxx_assert(__ret == 0);
}
void
lock()
{
- int __ret = pthread_rwlock_wrlock(&_M_rwlock);
+ int __ret = __glibcxx_rwlock_wrlock(&_M_rwlock);
if (__ret == EDEADLK)
__throw_system_error(int(errc::resource_deadlock_would_occur));
// Errors not handled: EINVAL
bool
try_lock()
{
- int __ret = pthread_rwlock_trywrlock(&_M_rwlock);
+ int __ret = __glibcxx_rwlock_trywrlock(&_M_rwlock);
if (__ret == EBUSY) return false;
// Errors not handled: EINVAL
__glibcxx_assert(__ret == 0);
void
unlock()
{
- int __ret __attribute((__unused__)) = pthread_rwlock_unlock(&_M_rwlock);
+ int __ret __attribute((__unused__)) = __glibcxx_rwlock_unlock(&_M_rwlock);
// Errors not handled: EPERM, EBUSY, EINVAL
__glibcxx_assert(__ret == 0);
}
// is okay based on the current specification of forward progress
// guarantees by the standard.
do
- __ret = pthread_rwlock_rdlock(&_M_rwlock);
+ __ret = __glibcxx_rwlock_rdlock(&_M_rwlock);
while (__ret == EAGAIN);
if (__ret == EDEADLK)
__throw_system_error(int(errc::resource_deadlock_would_occur));
bool
try_lock_shared()
{
- int __ret = pthread_rwlock_tryrdlock(&_M_rwlock);
+ int __ret = __glibcxx_rwlock_tryrdlock(&_M_rwlock);
// If the maximum number of read locks has been exceeded, we just fail
// to acquire the lock. Unlike for lock(), we are not allowed to throw
// an exception.
}
};
#endif
+ /// @endcond
-#if __cplusplus > 201402L
+#ifdef __cpp_lib_shared_mutex
/// The standard shared mutex type.
class shared_mutex
{
// Exclusive ownership
void lock() { _M_impl.lock(); }
- bool try_lock() { return _M_impl.try_lock(); }
+ [[nodiscard]] bool try_lock() { return _M_impl.try_lock(); }
void unlock() { _M_impl.unlock(); }
// Shared ownership
void lock_shared() { _M_impl.lock_shared(); }
- bool try_lock_shared() { return _M_impl.try_lock_shared(); }
+ [[nodiscard]] bool try_lock_shared() { return _M_impl.try_lock_shared(); }
void unlock_shared() { _M_impl.unlock_shared(); }
#if _GLIBCXX_USE_PTHREAD_RWLOCK_T
__shared_mutex_cv _M_impl;
#endif
};
-#endif // C++17
+#endif // __cpp_lib_shared_mutex
+ /// @cond undocumented
#if _GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK
using __shared_timed_mutex_base = __shared_mutex_pthread;
#else
using __shared_timed_mutex_base = __shared_mutex_cv;
#endif
+ /// @endcond
/// The standard shared timed mutex type.
class shared_timed_mutex
using _Base = __shared_timed_mutex_base;
// Must use the same clock as condition_variable for __shared_mutex_cv.
- typedef chrono::system_clock __clock_t;
+#ifdef _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK
+ using __clock_t = chrono::steady_clock;
+#else
+ using __clock_t = chrono::system_clock;
+#endif
public:
shared_timed_mutex() = default;
// Exclusive ownership
void lock() { _Base::lock(); }
- bool try_lock() { return _Base::try_lock(); }
+ _GLIBCXX_NODISCARD bool try_lock() { return _Base::try_lock(); }
void unlock() { _Base::unlock(); }
template<typename _Rep, typename _Period>
+ _GLIBCXX_NODISCARD
bool
- try_lock_for(const chrono::duration<_Rep, _Period>& __rel_time)
+ try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
{
- return try_lock_until(__clock_t::now() + __rel_time);
+ auto __rt = chrono::duration_cast<__clock_t::duration>(__rtime);
+ if (ratio_greater<__clock_t::period, _Period>())
+ ++__rt;
+ return try_lock_until(__clock_t::now() + __rt);
}
// Shared ownership
void lock_shared() { _Base::lock_shared(); }
+ _GLIBCXX_NODISCARD
bool try_lock_shared() { return _Base::try_lock_shared(); }
void unlock_shared() { _Base::unlock_shared(); }
template<typename _Rep, typename _Period>
+ _GLIBCXX_NODISCARD
bool
- try_lock_shared_for(const chrono::duration<_Rep, _Period>& __rel_time)
+ try_lock_shared_for(const chrono::duration<_Rep, _Period>& __rtime)
{
- return try_lock_shared_until(__clock_t::now() + __rel_time);
+ auto __rt = chrono::duration_cast<__clock_t::duration>(__rtime);
+ if (ratio_greater<__clock_t::period, _Period>())
+ ++__rt;
+ return try_lock_shared_until(__clock_t::now() + __rt);
}
#if _GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK
// Exclusive ownership
template<typename _Duration>
+ _GLIBCXX_NODISCARD
bool
- try_lock_until(const chrono::time_point<__clock_t, _Duration>& __atime)
+ try_lock_until(const chrono::time_point<chrono::system_clock,
+ _Duration>& __atime)
{
auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
static_cast<long>(__ns.count())
};
- int __ret = pthread_rwlock_timedwrlock(&_M_rwlock, &__ts);
+ int __ret = __glibcxx_rwlock_timedwrlock(&_M_rwlock, &__ts);
// On self-deadlock, we just fail to acquire the lock. Technically,
// the program violated the precondition.
if (__ret == ETIMEDOUT || __ret == EDEADLK)
return true;
}
+#ifdef _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK
+ template<typename _Duration>
+ _GLIBCXX_NODISCARD
+ bool
+ try_lock_until(const chrono::time_point<chrono::steady_clock,
+ _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())
+ };
+
+ int __ret = pthread_rwlock_clockwrlock(&_M_rwlock, CLOCK_MONOTONIC,
+ &__ts);
+ // On self-deadlock, we just fail to acquire the lock. Technically,
+ // the program violated the precondition.
+ if (__ret == ETIMEDOUT || __ret == EDEADLK)
+ return false;
+ // Errors not handled: EINVAL
+ __glibcxx_assert(__ret == 0);
+ return true;
+ }
+#endif
+
template<typename _Clock, typename _Duration>
+ _GLIBCXX_NODISCARD
bool
- try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time)
+ try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
{
- // DR 887 - Sync unknown clock to known clock.
- const typename _Clock::time_point __c_entry = _Clock::now();
- const __clock_t::time_point __s_entry = __clock_t::now();
- const auto __delta = __abs_time - __c_entry;
- const auto __s_atime = __s_entry + __delta;
- return try_lock_until(__s_atime);
+#if __cplusplus > 201703L
+ static_assert(chrono::is_clock_v<_Clock>);
+#endif
+ // The user-supplied clock may not tick at the same rate as
+ // steady_clock, so we must loop in order to guarantee that
+ // the timeout has expired before returning false.
+ typename _Clock::time_point __now = _Clock::now();
+ do {
+ auto __rtime = __atime - __now;
+ if (try_lock_for(__rtime))
+ return true;
+ __now = _Clock::now();
+ } while (__atime > __now);
+ return false;
}
// Shared ownership
template<typename _Duration>
+ _GLIBCXX_NODISCARD
bool
- try_lock_shared_until(const chrono::time_point<__clock_t,
+ try_lock_shared_until(const chrono::time_point<chrono::system_clock,
_Duration>& __atime)
{
auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
// mistaken for a spurious failure, which might help users realise
// there is a deadlock.
do
- __ret = pthread_rwlock_timedrdlock(&_M_rwlock, &__ts);
+ __ret = __glibcxx_rwlock_timedrdlock(&_M_rwlock, &__ts);
while (__ret == EAGAIN || __ret == EDEADLK);
if (__ret == ETIMEDOUT)
return false;
return true;
}
+#ifdef _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK
+ template<typename _Duration>
+ _GLIBCXX_NODISCARD
+ bool
+ try_lock_shared_until(const chrono::time_point<chrono::steady_clock,
+ _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())
+ };
+
+ int __ret = pthread_rwlock_clockrdlock(&_M_rwlock, CLOCK_MONOTONIC,
+ &__ts);
+ // On self-deadlock, we just fail to acquire the lock. Technically,
+ // the program violated the precondition.
+ if (__ret == ETIMEDOUT || __ret == EDEADLK)
+ return false;
+ // Errors not handled: EINVAL
+ __glibcxx_assert(__ret == 0);
+ return true;
+ }
+#endif
+
template<typename _Clock, typename _Duration>
+ _GLIBCXX_NODISCARD
bool
try_lock_shared_until(const chrono::time_point<_Clock,
- _Duration>& __abs_time)
+ _Duration>& __atime)
{
- // DR 887 - Sync unknown clock to known clock.
- const typename _Clock::time_point __c_entry = _Clock::now();
- const __clock_t::time_point __s_entry = __clock_t::now();
- const auto __delta = __abs_time - __c_entry;
- const auto __s_atime = __s_entry + __delta;
- return try_lock_shared_until(__s_atime);
+#if __cplusplus > 201703L
+ static_assert(chrono::is_clock_v<_Clock>);
+#endif
+ // The user-supplied clock may not tick at the same rate as
+ // steady_clock, so we must loop in order to guarantee that
+ // the timeout has expired before returning false.
+ typename _Clock::time_point __now = _Clock::now();
+ do {
+ auto __rtime = __atime - __now;
+ if (try_lock_shared_for(__rtime))
+ return true;
+ __now = _Clock::now();
+ } while (__atime > __now);
+ return false;
}
#else // ! (_GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK)
// Exclusive ownership
template<typename _Clock, typename _Duration>
+ _GLIBCXX_NODISCARD
bool
try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time)
{
// Shared ownership
template <typename _Clock, typename _Duration>
+ _GLIBCXX_NODISCARD
bool
try_lock_shared_until(const chrono::time_point<_Clock,
_Duration>& __abs_time)
_M_owns = true;
}
+ _GLIBCXX_NODISCARD
bool
try_lock()
{
}
template<typename _Rep, typename _Period>
+ _GLIBCXX_NODISCARD
bool
try_lock_for(const chrono::duration<_Rep, _Period>& __rel_time)
{
}
template<typename _Clock, typename _Duration>
+ _GLIBCXX_NODISCARD
bool
try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time)
{
unlock()
{
if (!_M_owns)
- __throw_system_error(int(errc::resource_deadlock_would_occur));
+ __throw_system_error(int(errc::operation_not_permitted));
_M_pm->unlock_shared();
_M_owns = false;
}
release() noexcept
{
_M_owns = false;
- return std::exchange(_M_pm, nullptr);
+ return std::__exchange(_M_pm, nullptr);
}
// Getters
+ _GLIBCXX_NODISCARD
bool owns_lock() const noexcept { return _M_owns; }
explicit operator bool() const noexcept { return _M_owns; }
+ _GLIBCXX_NODISCARD
mutex_type* mutex() const noexcept { return _M_pm; }
private:
};
/// Swap specialization for shared_lock
+ /// @relates shared_mutex
template<typename _Mutex>
void
swap(shared_lock<_Mutex>& __x, shared_lock<_Mutex>& __y) noexcept
{ __x.swap(__y); }
-#endif // _GLIBCXX_USE_C99_STDINT_TR1
-
- // @} group mutexes
+ /// @} group mutexes
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
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