Function _rt_mq_recv

src/ipc.c:3764–3925

* @brief This function will receive a message from message queue object, * if there is no message in messagequeue object, the thread shall wait for a specified time. * * @note Only when there is mail in the mailbox, the receiving thread can get the mail immediately and return RT_EOK, * otherwise the receiving thread will be suspended until timeout. * If th

 *           If the return value is any other values, it means that the mailbox release failed.
 */
static rt_ssize_t _rt_mq_recv(rt_mq_t mq,
                              void *buffer,
                              rt_size_t size,
                              rt_int32_t *prio,
                              rt_int32_t timeout,
                              int suspend_flag)
{
    struct rt_thread *thread;
    rt_base_t level;
    struct rt_mq_message *msg;
    rt_uint32_t tick_delta;
    rt_err_t ret;
    rt_size_t len;

    RT_UNUSED(prio);

    /* parameter check */
    RT_ASSERT(mq != RT_NULL);
    RT_ASSERT(rt_object_get_type(&mq->parent.parent) == RT_Object_Class_MessageQueue);
    RT_ASSERT(buffer != RT_NULL);
    RT_ASSERT(size != 0);

    /* current context checking */
    RT_DEBUG_SCHEDULER_AVAILABLE(timeout != 0);

    /* initialize delta tick */
    tick_delta = 0;
    /* get current thread */
    thread = rt_thread_self();
    RT_OBJECT_HOOK_CALL(rt_object_trytake_hook, (&(mq->parent.parent)));

    level = rt_spin_lock_irqsave(&(mq->spinlock));

    /* for non-blocking call */
    if (mq->entry == 0 && timeout == 0)
    {
        rt_spin_unlock_irqrestore(&(mq->spinlock), level);

        return -RT_ETIMEOUT;
    }

    /* message queue is empty */
    while (mq->entry == 0)
    {
        /* reset error number in thread */
        thread->error = -RT_EINTR;

        /* no waiting, return timeout */
        if (timeout == 0)
        {
            /* enable interrupt */
            rt_spin_unlock_irqrestore(&(mq->spinlock), level);

            thread->error = -RT_ETIMEOUT;

            return -RT_ETIMEOUT;
        }