// <shared_mutex> -*- C++ -*-
-// Copyright (C) 2013-2015 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 <mutex>
-#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
-#define __cpp_lib_shared_timed_mutex 201402
+#ifdef __cpp_lib_shared_mutex // C++ >= 17 && hosted && gthread
+ class shared_mutex;
+#endif
- /// shared_timed_mutex
- class shared_timed_mutex
+ 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)
{
-#ifdef _GLIBCXX_USE_PTHREAD_RWLOCK_T
- typedef chrono::system_clock __clock_t;
+ 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
+ {
+ friend class shared_timed_mutex;
#ifdef PTHREAD_RWLOCK_INITIALIZER
pthread_rwlock_t _M_rwlock = PTHREAD_RWLOCK_INITIALIZER;
public:
- shared_timed_mutex() = default;
- ~shared_timed_mutex() = default;
+ __shared_mutex_pthread() = default;
+ ~__shared_mutex_pthread() = default;
#else
pthread_rwlock_t _M_rwlock;
public:
- shared_timed_mutex()
+ __shared_mutex_pthread()
{
- int __ret = pthread_rwlock_init(&_M_rwlock, NULL);
+ int __ret = __glibcxx_rwlock_init(&_M_rwlock);
if (__ret == ENOMEM)
- throw bad_alloc();
+ __throw_bad_alloc();
else if (__ret == EAGAIN)
__throw_system_error(int(errc::resource_unavailable_try_again));
else if (__ret == EPERM)
__throw_system_error(int(errc::operation_not_permitted));
// Errors not handled: EBUSY, EINVAL
- _GLIBCXX_DEBUG_ASSERT(__ret == 0);
+ __glibcxx_assert(__ret == 0);
}
- ~shared_timed_mutex()
+ ~__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_DEBUG_ASSERT(__ret == 0);
+ __glibcxx_assert(__ret == 0);
}
#endif
- shared_timed_mutex(const shared_timed_mutex&) = delete;
- shared_timed_mutex& operator=(const shared_timed_mutex&) = delete;
-
- // Exclusive ownership
+ __shared_mutex_pthread(const __shared_mutex_pthread&) = delete;
+ __shared_mutex_pthread& operator=(const __shared_mutex_pthread&) = delete;
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
- _GLIBCXX_DEBUG_ASSERT(__ret == 0);
+ __glibcxx_assert(__ret == 0);
}
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_DEBUG_ASSERT(__ret == 0);
+ __glibcxx_assert(__ret == 0);
return true;
}
-#if _GTHREAD_USE_MUTEX_TIMEDLOCK
- template<typename _Rep, typename _Period>
- bool
- try_lock_for(const chrono::duration<_Rep, _Period>& __rel_time)
- {
- return try_lock_until(__clock_t::now() + __rel_time);
- }
-
- template<typename _Duration>
- bool
- 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())
- };
-
- int __ret = pthread_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 false;
- // Errors not handled: EINVAL
- _GLIBCXX_DEBUG_ASSERT(__ret == 0);
- return true;
- }
-
- template<typename _Clock, typename _Duration>
- bool
- try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time)
- {
- // 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);
- }
-#endif
-
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_DEBUG_ASSERT(__ret == 0);
+ __glibcxx_assert(__ret == 0);
}
// Shared ownership
// 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));
// Errors not handled: EINVAL
- _GLIBCXX_DEBUG_ASSERT(__ret == 0);
+ __glibcxx_assert(__ret == 0);
}
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.
if (__ret == EBUSY || __ret == EAGAIN) return false;
// Errors not handled: EINVAL
- _GLIBCXX_DEBUG_ASSERT(__ret == 0);
+ __glibcxx_assert(__ret == 0);
return true;
}
-#if _GTHREAD_USE_MUTEX_TIMEDLOCK
- template<typename _Rep, typename _Period>
- bool
- try_lock_shared_for(const chrono::duration<_Rep, _Period>& __rel_time)
- {
- return try_lock_shared_until(__clock_t::now() + __rel_time);
- }
-
- template<typename _Duration>
- bool
- try_lock_shared_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())
- };
-
- int __ret;
- // Unlike for lock(), we are not allowed to throw an exception so if
- // the maximum number of read locks has been exceeded, or we would
- // deadlock, we just try to acquire the lock again (and will time out
- // eventually).
- // In cases where we would exceed the maximum number of read locks
- // throughout the whole time until the timeout, we will fail to
- // acquire the lock even if it would be logically free; however, this
- // is allowed by the standard, and we made a "strong effort"
- // (see C++14 30.4.1.4p26).
- // For cases where the implementation detects a deadlock we
- // intentionally block and timeout so that an early return isn't
- // mistaken for a spurious failure, which might help users realise
- // there is a deadlock.
- do
- __ret = pthread_rwlock_timedrdlock(&_M_rwlock, &__ts);
- while (__ret == EAGAIN || __ret == EDEADLK);
- if (__ret == ETIMEDOUT)
- return false;
- // Errors not handled: EINVAL
- _GLIBCXX_DEBUG_ASSERT(__ret == 0);
- return true;
- }
-
- template<typename _Clock, typename _Duration>
- bool
- try_lock_shared_until(const chrono::time_point<_Clock,
- _Duration>& __abs_time)
- {
- // 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);
- }
-#endif
-
void
unlock_shared()
{
unlock();
}
-#else // ! _GLIBCXX_USE_PTHREAD_RWLOCK_T
+ void* native_handle() { return &_M_rwlock; }
+ };
+#endif
- // Must use the same clock as condition_variable
- typedef chrono::system_clock __clock_t;
+#if ! (_GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK)
+ /// A shared mutex type implemented using std::condition_variable.
+ class __shared_mutex_cv
+ {
+ friend class shared_timed_mutex;
// Based on Howard Hinnant's reference implementation from N2406.
unsigned _M_readers() const { return _M_state & _S_max_readers; }
public:
- shared_timed_mutex() : _M_state(0) {}
+ __shared_mutex_cv() : _M_state(0) {}
- ~shared_timed_mutex()
+ ~__shared_mutex_cv()
{
- _GLIBCXX_DEBUG_ASSERT( _M_state == 0 );
+ __glibcxx_assert( _M_state == 0 );
}
- shared_timed_mutex(const shared_timed_mutex&) = delete;
- shared_timed_mutex& operator=(const shared_timed_mutex&) = delete;
+ __shared_mutex_cv(const __shared_mutex_cv&) = delete;
+ __shared_mutex_cv& operator=(const __shared_mutex_cv&) = delete;
// Exclusive ownership
return false;
}
- template<typename _Rep, typename _Period>
- bool
- try_lock_for(const chrono::duration<_Rep, _Period>& __rel_time)
- {
- return try_lock_until(__clock_t::now() + __rel_time);
- }
-
- template<typename _Clock, typename _Duration>
- bool
- try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time)
- {
- unique_lock<mutex> __lk(_M_mut);
- if (!_M_gate1.wait_until(__lk, __abs_time,
- [=]{ return !_M_write_entered(); }))
- {
- return false;
- }
- _M_state |= _S_write_entered;
- if (!_M_gate2.wait_until(__lk, __abs_time,
- [=]{ return _M_readers() == 0; }))
- {
- _M_state ^= _S_write_entered;
- // Wake all threads blocked while the write-entered flag was set.
- _M_gate1.notify_all();
- return false;
- }
- return true;
- }
-
void
unlock()
{
lock_guard<mutex> __lk(_M_mut);
- _GLIBCXX_DEBUG_ASSERT( _M_write_entered() );
+ __glibcxx_assert( _M_write_entered() );
_M_state = 0;
// call notify_all() while mutex is held so that another thread can't
// lock and unlock the mutex then destroy *this before we make the call.
return false;
}
- template<typename _Rep, typename _Period>
- bool
- try_lock_shared_for(const chrono::duration<_Rep, _Period>& __rel_time)
- {
- return try_lock_shared_until(__clock_t::now() + __rel_time);
- }
-
- template <typename _Clock, typename _Duration>
- bool
- try_lock_shared_until(const chrono::time_point<_Clock,
- _Duration>& __abs_time)
- {
- unique_lock<mutex> __lk(_M_mut);
- if (!_M_gate1.wait_until(__lk, __abs_time,
- [=]{ return _M_state < _S_max_readers; }))
- {
- return false;
- }
- ++_M_state;
- return true;
- }
-
void
unlock_shared()
{
lock_guard<mutex> __lk(_M_mut);
- _GLIBCXX_DEBUG_ASSERT( _M_readers() > 0 );
+ __glibcxx_assert( _M_readers() > 0 );
auto __prev = _M_state--;
if (_M_write_entered())
{
_M_gate1.notify_one();
}
}
-#endif // ! _GLIBCXX_USE_PTHREAD_RWLOCK_T
+ };
+#endif
+ /// @endcond
+
+#ifdef __cpp_lib_shared_mutex
+ /// The standard shared mutex type.
+ class shared_mutex
+ {
+ public:
+ shared_mutex() = default;
+ ~shared_mutex() = default;
+
+ shared_mutex(const shared_mutex&) = delete;
+ shared_mutex& operator=(const shared_mutex&) = delete;
+
+ // Exclusive ownership
+
+ void lock() { _M_impl.lock(); }
+ [[nodiscard]] bool try_lock() { return _M_impl.try_lock(); }
+ void unlock() { _M_impl.unlock(); }
+
+ // Shared ownership
+
+ void lock_shared() { _M_impl.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
+ typedef void* native_handle_type;
+ native_handle_type native_handle() { return _M_impl.native_handle(); }
+
+ private:
+ __shared_mutex_pthread _M_impl;
+#else
+ private:
+ __shared_mutex_cv _M_impl;
+#endif
+ };
+#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
+ : private __shared_timed_mutex_base
+ {
+ using _Base = __shared_timed_mutex_base;
+
+ // Must use the same clock as condition_variable for __shared_mutex_cv.
+#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;
+ ~shared_timed_mutex() = default;
+
+ shared_timed_mutex(const shared_timed_mutex&) = delete;
+ shared_timed_mutex& operator=(const shared_timed_mutex&) = delete;
+
+ // Exclusive ownership
+
+ void lock() { _Base::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>& __rtime)
+ {
+ 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>& __rtime)
+ {
+ 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<chrono::system_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 = __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 false;
+ // Errors not handled: EINVAL
+ __glibcxx_assert(__ret == 0);
+ 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>& __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<chrono::system_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;
+ // Unlike for lock(), we are not allowed to throw an exception so if
+ // the maximum number of read locks has been exceeded, or we would
+ // deadlock, we just try to acquire the lock again (and will time out
+ // eventually).
+ // In cases where we would exceed the maximum number of read locks
+ // throughout the whole time until the timeout, we will fail to
+ // acquire the lock even if it would be logically free; however, this
+ // is allowed by the standard, and we made a "strong effort"
+ // (see C++14 30.4.1.4p26).
+ // For cases where the implementation detects a deadlock we
+ // intentionally block and timeout so that an early return isn't
+ // mistaken for a spurious failure, which might help users realise
+ // there is a deadlock.
+ do
+ __ret = __glibcxx_rwlock_timedrdlock(&_M_rwlock, &__ts);
+ while (__ret == EAGAIN || __ret == EDEADLK);
+ if (__ret == ETIMEDOUT)
+ return false;
+ // Errors not handled: EINVAL
+ __glibcxx_assert(__ret == 0);
+ 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>& __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)
+ {
+ unique_lock<mutex> __lk(_M_mut);
+ if (!_M_gate1.wait_until(__lk, __abs_time,
+ [=]{ return !_M_write_entered(); }))
+ {
+ return false;
+ }
+ _M_state |= _S_write_entered;
+ if (!_M_gate2.wait_until(__lk, __abs_time,
+ [=]{ return _M_readers() == 0; }))
+ {
+ _M_state ^= _S_write_entered;
+ // Wake all threads blocked while the write-entered flag was set.
+ _M_gate1.notify_all();
+ return false;
+ }
+ return true;
+ }
+
+ // Shared ownership
+
+ template <typename _Clock, typename _Duration>
+ _GLIBCXX_NODISCARD
+ bool
+ try_lock_shared_until(const chrono::time_point<_Clock,
+ _Duration>& __abs_time)
+ {
+ unique_lock<mutex> __lk(_M_mut);
+ if (!_M_gate1.wait_until(__lk, __abs_time,
+ [=]{ return _M_state < _S_max_readers; }))
+ {
+ return false;
+ }
+ ++_M_state;
+ return true;
+ }
+
+#endif // _GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK
};
#endif // _GLIBCXX_HAS_GTHREADS
shared_lock() noexcept : _M_pm(nullptr), _M_owns(false) { }
explicit
- shared_lock(mutex_type& __m) : _M_pm(&__m), _M_owns(true)
+ shared_lock(mutex_type& __m)
+ : _M_pm(std::__addressof(__m)), _M_owns(true)
{ __m.lock_shared(); }
shared_lock(mutex_type& __m, defer_lock_t) noexcept
- : _M_pm(&__m), _M_owns(false) { }
+ : _M_pm(std::__addressof(__m)), _M_owns(false) { }
shared_lock(mutex_type& __m, try_to_lock_t)
- : _M_pm(&__m), _M_owns(__m.try_lock_shared()) { }
+ : _M_pm(std::__addressof(__m)), _M_owns(__m.try_lock_shared()) { }
shared_lock(mutex_type& __m, adopt_lock_t)
- : _M_pm(&__m), _M_owns(true) { }
+ : _M_pm(std::__addressof(__m)), _M_owns(true) { }
template<typename _Clock, typename _Duration>
shared_lock(mutex_type& __m,
const chrono::time_point<_Clock, _Duration>& __abs_time)
- : _M_pm(&__m), _M_owns(__m.try_lock_shared_until(__abs_time)) { }
+ : _M_pm(std::__addressof(__m)),
+ _M_owns(__m.try_lock_shared_until(__abs_time)) { }
template<typename _Rep, typename _Period>
shared_lock(mutex_type& __m,
const chrono::duration<_Rep, _Period>& __rel_time)
- : _M_pm(&__m), _M_owns(__m.try_lock_shared_for(__rel_time)) { }
+ : _M_pm(std::__addressof(__m)),
+ _M_owns(__m.try_lock_shared_for(__rel_time)) { }
~shared_lock()
{
_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