SizedQueue#push

static VALUE
rb_szqueue_push(int argc, VALUE *argv, VALUE self)
{
    struct rb_szqueue *sq = szqueue_ptr(self);
    int should_block = szqueue_push_should_block(argc, argv);

    while (queue_length(self, &sq->q) >= sq->max) {
        if (!should_block) {
            rb_raise(rb_eThreadError, "queue full");
        }
        else if (queue_closed_p(self)) {
            break;
        }
        else {
            rb_execution_context_t *ec = GET_EC();
            COROUTINE_STACK_LOCAL(struct queue_waiter, qw);
            struct list_head *pushq = szqueue_pushq(sq);

            qw->w.self = self;
            qw->w.th = ec->thread_ptr;
            qw->w.fiber = ec->fiber_ptr;

            qw->as.sq = sq;
            list_add_tail(pushq, &qw->w.node);
            sq->num_waiting_push++;

            rb_ensure(queue_sleep, self, szqueue_sleep_done, (VALUE)qw);
        }
    }

    if (queue_closed_p(self)) {
        raise_closed_queue_error(self);
    }

    return queue_do_push(self, &sq->q, argv[0]);
}