enqueue() - Rust

mod bindings;
use bindings::*;

pub fn enqueue(rp: *mut proc) {
    let q: i32 = rp.p_priority;
    let rdy_head: *mut proc;
    let rdy_tail: *mut proc;

    // assert!(proc_is_runnable(rp));

    // assert!(q > 0);

    rdy_head = get_cpu_var(rp.p_cpu, run_q_head);
    rdy_tail = get_cpu_var(rp.p_cpu, run_q_tail);

    // Now add the process to the queue
    if !rdy_head[&q] {
        rdy_head[&q] = rdy_tail[q] = rp;
        //rp.p_nextready = std::ptr::null();
    }
    else {
        rdy_tail[&q].p_nextready = rp;
        rdy_tail[&q] = rp;
        //rp.p_nextready = std::ptr::null();
    }

     /*
     * enqueueing a process with a higher priority than the current one,
     * it gets preempted. The current process must be preemptible. Testing
     * the priority also makes sure that a process does not preempt itself
     */

    if cpuid == rp.p_cpu {
        let p: *mut proc;
        p = get_cpulocal_var(proc_ptr);
        assert!(p);

        if (p.p_priority > rp.p_priority) && p.s_flags & PREEMPTIBLE {
            RTS_SET(p, RTS_PREEMPTED);
        }

    }
    else if get_cpu_var(rp.p_cpu, cpu_is_idle) {
        smp_schedule(rp.p_cpu);
    }

    read_tsc_64(&(get_cpulocal_var(proc_ptr).p_accounting.enter_queue));
}