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Diffstat (limited to 'boost/interprocess/sync/spin/condition.hpp')
| -rw-r--r-- | boost/interprocess/sync/spin/condition.hpp | 295 |
1 files changed, 295 insertions, 0 deletions
diff --git a/boost/interprocess/sync/spin/condition.hpp b/boost/interprocess/sync/spin/condition.hpp new file mode 100644 index 0000000..5a37d9b --- /dev/null +++ b/boost/interprocess/sync/spin/condition.hpp @@ -0,0 +1,295 @@ +////////////////////////////////////////////////////////////////////////////// +// +// (C) Copyright Ion Gaztanaga 2005-2011. Distributed under the Boost +// Software License, Version 1.0. (See accompanying file +// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) +// +// See http://www.boost.org/libs/interprocess for documentation. +// +////////////////////////////////////////////////////////////////////////////// + +#ifndef BOOST_INTERPROCESS_DETAIL_SPIN_CONDITION_HPP +#define BOOST_INTERPROCESS_DETAIL_SPIN_CONDITION_HPP + +#include <boost/interprocess/detail/config_begin.hpp> +#include <boost/interprocess/detail/workaround.hpp> +#include <boost/interprocess/sync/spin/mutex.hpp> +#include <boost/interprocess/detail/posix_time_types_wrk.hpp> +#include <boost/interprocess/detail/atomic.hpp> +#include <boost/interprocess/sync/scoped_lock.hpp> +#include <boost/interprocess/exceptions.hpp> +#include <boost/interprocess/detail/os_thread_functions.hpp> +#include <boost/move/move.hpp> +#include <boost/cstdint.hpp> + +namespace boost { +namespace interprocess { +namespace ipcdetail { + +class spin_condition +{ + spin_condition(const spin_condition &); + spin_condition &operator=(const spin_condition &); + public: + spin_condition(); + ~spin_condition(); + + void notify_one(); + void notify_all(); + + template <typename L> + bool timed_wait(L& lock, const boost::posix_time::ptime &abs_time) + { + if(abs_time == boost::posix_time::pos_infin){ + this->wait(lock); + return true; + } + if (!lock) + throw lock_exception(); + return this->do_timed_wait(abs_time, *lock.mutex()); + } + + template <typename L, typename Pr> + bool timed_wait(L& lock, const boost::posix_time::ptime &abs_time, Pr pred) + { + if(abs_time == boost::posix_time::pos_infin){ + this->wait(lock, pred); + return true; + } + if (!lock) + throw lock_exception(); + while (!pred()){ + if (!this->do_timed_wait(abs_time, *lock.mutex())) + return pred(); + } + return true; + } + + template <typename L> + void wait(L& lock) + { + if (!lock) + throw lock_exception(); + do_wait(*lock.mutex()); + } + + template <typename L, typename Pr> + void wait(L& lock, Pr pred) + { + if (!lock) + throw lock_exception(); + + while (!pred()) + do_wait(*lock.mutex()); + } + + template<class InterprocessMutex> + void do_wait(InterprocessMutex &mut); + + template<class InterprocessMutex> + bool do_timed_wait(const boost::posix_time::ptime &abs_time, InterprocessMutex &mut); + + private: + template<class InterprocessMutex> + bool do_timed_wait(bool tout_enabled, const boost::posix_time::ptime &abs_time, InterprocessMutex &mut); + + enum { SLEEP = 0, NOTIFY_ONE, NOTIFY_ALL }; + spin_mutex m_enter_mut; + volatile boost::uint32_t m_command; + volatile boost::uint32_t m_num_waiters; + void notify(boost::uint32_t command); +}; + +inline spin_condition::spin_condition() +{ + //Note that this class is initialized to zero. + //So zeroed memory can be interpreted as an initialized + //condition variable + m_command = SLEEP; + m_num_waiters = 0; +} + +inline spin_condition::~spin_condition() +{ + //Trivial destructor +} + +inline void spin_condition::notify_one() +{ + this->notify(NOTIFY_ONE); +} + +inline void spin_condition::notify_all() +{ + this->notify(NOTIFY_ALL); +} + +inline void spin_condition::notify(boost::uint32_t command) +{ + //This mutex guarantees that no other thread can enter to the + //do_timed_wait method logic, so that thread count will be + //constant until the function writes a NOTIFY_ALL command. + //It also guarantees that no other notification can be signaled + //on this spin_condition before this one ends + m_enter_mut.lock(); + + //Return if there are no waiters + if(!atomic_read32(&m_num_waiters)) { + m_enter_mut.unlock(); + return; + } + + //Notify that all threads should execute wait logic + while(SLEEP != atomic_cas32(const_cast<boost::uint32_t*>(&m_command), command, SLEEP)){ + thread_yield(); + } +/* + //Wait until the threads are woken + while(SLEEP != atomic_cas32(const_cast<boost::uint32_t*>(&m_command), 0)){ + thread_yield(); + } +*/ + //The enter mutex will rest locked until the last waiting thread unlocks it +} + +template<class InterprocessMutex> +inline void spin_condition::do_wait(InterprocessMutex &mut) +{ + this->do_timed_wait(false, boost::posix_time::ptime(), mut); +} + +template<class InterprocessMutex> +inline bool spin_condition::do_timed_wait + (const boost::posix_time::ptime &abs_time, InterprocessMutex &mut) +{ + return this->do_timed_wait(true, abs_time, mut); +} + +template<class InterprocessMutex> +inline bool spin_condition::do_timed_wait(bool tout_enabled, + const boost::posix_time::ptime &abs_time, + InterprocessMutex &mut) +{ + boost::posix_time::ptime now = microsec_clock::universal_time(); + + if(tout_enabled){ + if(now >= abs_time) return false; + } + + typedef boost::interprocess::scoped_lock<spin_mutex> InternalLock; + //The enter mutex guarantees that while executing a notification, + //no other thread can execute the do_timed_wait method. + { + //--------------------------------------------------------------- + InternalLock lock; + if(tout_enabled){ + InternalLock dummy(m_enter_mut, abs_time); + lock = boost::move(dummy); + } + else{ + InternalLock dummy(m_enter_mut); + lock = boost::move(dummy); + } + + if(!lock) + return false; + //--------------------------------------------------------------- + //We increment the waiting thread count protected so that it will be + //always constant when another thread enters the notification logic. + //The increment marks this thread as "waiting on spin_condition" + atomic_inc32(const_cast<boost::uint32_t*>(&m_num_waiters)); + + //We unlock the external mutex atomically with the increment + mut.unlock(); + } + + //By default, we suppose that no timeout has happened + bool timed_out = false, unlock_enter_mut= false; + + //Loop until a notification indicates that the thread should + //exit or timeout occurs + while(1){ + //The thread sleeps/spins until a spin_condition commands a notification + //Notification occurred, we will lock the checking mutex so that + while(atomic_read32(&m_command) == SLEEP){ + thread_yield(); + + //Check for timeout + if(tout_enabled){ + now = microsec_clock::universal_time(); + + if(now >= abs_time){ + //If we can lock the mutex it means that no notification + //is being executed in this spin_condition variable + timed_out = m_enter_mut.try_lock(); + + //If locking fails, indicates that another thread is executing + //notification, so we play the notification game + if(!timed_out){ + //There is an ongoing notification, we will try again later + continue; + } + //No notification in execution, since enter mutex is locked. + //We will execute time-out logic, so we will decrement count, + //release the enter mutex and return false. + break; + } + } + } + + //If a timeout occurred, the mutex will not execute checking logic + if(tout_enabled && timed_out){ + //Decrement wait count + atomic_dec32(const_cast<boost::uint32_t*>(&m_num_waiters)); + unlock_enter_mut = true; + break; + } + else{ + boost::uint32_t result = atomic_cas32 + (const_cast<boost::uint32_t*>(&m_command), SLEEP, NOTIFY_ONE); + if(result == SLEEP){ + //Other thread has been notified and since it was a NOTIFY one + //command, this thread must sleep again + continue; + } + else if(result == NOTIFY_ONE){ + //If it was a NOTIFY_ONE command, only this thread should + //exit. This thread has atomically marked command as sleep before + //so no other thread will exit. + //Decrement wait count. + unlock_enter_mut = true; + atomic_dec32(const_cast<boost::uint32_t*>(&m_num_waiters)); + break; + } + else{ + //If it is a NOTIFY_ALL command, all threads should return + //from do_timed_wait function. Decrement wait count. + unlock_enter_mut = 1 == atomic_dec32(const_cast<boost::uint32_t*>(&m_num_waiters)); + //Check if this is the last thread of notify_all waiters + //Only the last thread will release the mutex + if(unlock_enter_mut){ + atomic_cas32(const_cast<boost::uint32_t*>(&m_command), SLEEP, NOTIFY_ALL); + } + break; + } + } + } + + //Unlock the enter mutex if it is a single notification, if this is + //the last notified thread in a notify_all or a timeout has occurred + if(unlock_enter_mut){ + m_enter_mut.unlock(); + } + + //Lock external again before returning from the method + mut.lock(); + return !timed_out; +} + +} //namespace ipcdetail +} //namespace interprocess +} //namespace boost + +#include <boost/interprocess/detail/config_end.hpp> + +#endif //BOOST_INTERPROCESS_DETAIL_SPIN_CONDITION_HPP |