Thread::SizedQueue#max=

static VALUE
rb_szqueue_max_set(VALUE self, VALUE vmax)
{
    long max = NUM2LONG(vmax);
    long diff = 0;
    struct rb_szqueue *sq = szqueue_ptr(self);

    if (max <= 0) {
        rb_raise(rb_eArgError, "queue size must be positive");
    }
    if (max > sq->max) {
        diff = max - sq->max;
    }
    sq->max = max;
    sync_wakeup(szqueue_pushq(sq), diff);
    return vmax;
}