Function _futex_wait

components/lwp/lwp_futex.c:535–600

* @brief Wait on a futex if its value matches the expected value. * * @param[in] futex The futex to wait on * @param[in] lwp Lightweight process structure * @param[in] uaddr User-space address of futex value * @param[in] value Expected value to compare against * @param[in] timeout Optional timeout specification * @param[in] op_flags Operation flags (e.g. FUTEX_PRIVATE) * * @return int Ret

 *         - EAGAIN if value does not match
 */
static int _futex_wait(rt_futex_t futex, struct rt_lwp *lwp, int *uaddr,
                       int value, const struct timespec *timeout, int op_flags)
{
    rt_tick_t to;
    rt_thread_t thread;
    rt_err_t rc = -RT_EINTR;

    /**
     * Brief: Remove current thread from scheduler, besides appends it to
     * the waiting thread list of the futex. If the timeout is specified
     * a timer will be setup for current thread
     *
     * Note: Critical Section
     * - futex.waiting (RW; Protected by lwp_lock)
     * - the local cpu
     */
    _futex_lock(lwp, op_flags);
    if (*uaddr == value)
    {
        thread = rt_thread_self();

        if (timeout)
        {
            to = timeout->tv_sec * RT_TICK_PER_SECOND;
            to +=
                (timeout->tv_nsec * RT_TICK_PER_SECOND) / NANOSECOND_PER_SECOND;

            if (to < 0)
            {
                rc = -EINVAL;
                _futex_unlock(lwp, op_flags);
            }
            else
            {
                rt_enter_critical();
                rc = _suspend_thread_timeout_locked(thread, futex, to);
                _futex_unlock(lwp, op_flags);
                rt_exit_critical();
            }
        }
        else
        {
            rt_enter_critical();
            rc = _suspend_thread_locked(thread, futex);
            _futex_unlock(lwp, op_flags);
            rt_exit_critical();
        }

        if (rc == RT_EOK)
        {
            /* do schedule */
            rt_schedule();
            /* check errno */
            rc = rt_get_errno();
            rc = rc > 0 ? -rc : rc;
        }
    }
    else