timed_mutex.hpp

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// SPDX-License-Identifier: BSD-3-Clause
/* Copyright 2016-2020, Intel Corporation */
 
#ifndef LIBPMEMOBJ_CPP_TIMED_MUTEX_HPP
#define LIBPMEMOBJ_CPP_TIMED_MUTEX_HPP
 
#include <chrono>
 
#include <libpmemobj++/detail/conversions.hpp>
#include <libpmemobj/thread.h>
 
namespace pmem
{
 
namespace obj
{
 
class timed_mutex {
    typedef std::chrono::system_clock clock_type;
 
public:
    typedef PMEMmutex *native_handle_type;
 
    timed_mutex()
    {
        PMEMobjpool *pop;
        if ((pop = pmemobj_pool_by_ptr(&plock)) == nullptr)
            throw pmem::lock_error(
                1, std::generic_category(),
                "Persistent mutex not from persistent memory.");
 
        pmemobj_mutex_zero(pop, &plock);
    }
 
    ~timed_mutex() = default;
 
    void
    lock()
    {
        PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
        if (int ret = pmemobj_mutex_lock(pop, &this->plock))
            throw pmem::lock_error(ret, std::system_category(),
                           "Failed to lock a mutex.")
                .with_pmemobj_errormsg();
    }
 
    bool
    try_lock()
    {
        PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
        int ret = pmemobj_mutex_trylock(pop, &this->plock);
 
        if (ret == 0)
            return true;
        else if (ret == EBUSY)
            return false;
        else
            throw pmem::lock_error(ret, std::system_category(),
                           "Failed to lock a mutex.")
                .with_pmemobj_errormsg();
    }
 
    template <typename Clock, typename Duration>
    bool
    try_lock_until(
        const std::chrono::time_point<Clock, Duration> &timeout_time)
    {
        return timedlock_impl(timeout_time);
    }
 
    template <typename Rep, typename Period>
    bool
    try_lock_for(const std::chrono::duration<Rep, Period> &timeout_duration)
    {
        return timedlock_impl(clock_type::now() + timeout_duration);
    }
 
    void
    unlock()
    {
        PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
        int ret = pmemobj_mutex_unlock(pop, &this->plock);
        if (ret)
            throw pmem::lock_error(ret, std::system_category(),
                           "Failed to unlock a mutex.")
                .with_pmemobj_errormsg();
    }
 
    native_handle_type
    native_handle() noexcept
    {
        return &this->plock;
    }
 
    timed_mutex &operator=(const timed_mutex &) = delete;
 
    timed_mutex(const timed_mutex &) = delete;
 
private:
    template <typename Clock, typename Duration>
    bool
    timedlock_impl(const std::chrono::time_point<Clock, Duration> &abs_time)
    {
        PMEMobjpool *pop = pmemobj_pool_by_ptr(this);
 
        /* convert to my clock */
        const typename Clock::time_point their_now = Clock::now();
        const clock_type::time_point my_now = clock_type::now();
        const auto delta = abs_time - their_now;
        const auto my_abs = my_now + delta;
 
        struct timespec ts = detail::timepoint_to_timespec(my_abs);
 
        auto ret = pmemobj_mutex_timedlock(pop, &this->plock, &ts);
 
        if (ret == 0)
            return true;
        else if (ret == ETIMEDOUT)
            return false;
        else
            throw pmem::lock_error(ret, std::system_category(),
                           "Failed to lock a mutex");
    }
 
    PMEMmutex plock;
};
 
} /* namespace obj */
 
} /* namespace pmem */
 
#endif /* LIBPMEMOBJ_CPP_TIMED_MUTEX_HPP */