Function _futex_wake

components/lwp/lwp_futex.c:616–647

* @brief Wake up suspended threads from futex waiting list * * @param[in] futex The futex containing waiting threads * @param[in] lwp Lightweight process structure * @param[in] number Maximum number of threads to wake up * @param[in] op_flags Operation flags (e.g. FUTEX_PRIVATE) * * @return long Number of threads actually woken up * * @note The actual number of woken threads may be less t

 *       It performs a schedule after waking threads.
 */
static long _futex_wake(rt_futex_t futex, struct rt_lwp *lwp, int number,
                        int op_flags)
{
    long woken_cnt = 0;
    int is_empty = 0;

    /**
     * Brief: Wakeup a suspended thread on the futex waiting thread list
     *
     * Note: Critical Section
     * - the futex waiting_thread list (RW)
     */
    while (number && !is_empty)
    {
        _futex_lock(lwp, op_flags);
        if (rt_susp_list_dequeue(&futex->waiting_thread, RT_EOK))
        {
            number--;
            woken_cnt++;
            is_empty = RT_FALSE;
        }
        else
        {
            is_empty = RT_TRUE;
        }
        _futex_unlock(lwp, op_flags);
    }

    /* do schedule */
    rt_schedule();
    return woken_cnt;
}

/**
 * @brief Requeue threads from one futex waiting list to another