fix: scheduler: head node will never be scheduled, add a dummy head node

kernel/src/arch/riscv/board/virt/mod.rs

@@ -1,4 +1,4 @@
-pub const TIMER_TICKS: u64 = 100_000; // 100ms
+pub const TIMER_TICKS: u64 = 100_000;
 
 // devices
 pub const UART0_BASE: usize = 0x1000_0000;

kernel/src/entry.rs

@@ -2,7 +2,7 @@ use crate::plat::console::{set_console, ConsoleDevice, ConsoleDriver, CONSOLE};
 use crate::plat::lowlevel::{Hardware, LowLevel};
 use crate::plat::timer::{Timer, TimerOps};
 use crate::plat::trap::{Trap, TrapOps};
-use crate::scheduler::SCHEDULER;
+use crate::scheduler::{IDLE_THREAD, SCHEDULER};
 use core::cell::Cell;
 use core::sync::atomic::{AtomicUsize, Ordering};
 use fdt::Fdt;
@@ -35,6 +35,9 @@ pub fn rust_main() -> ! {
     Trap::init();
     Timer::init();
 
+    SCHEDULER.init();
+    SCHEDULER.add(&IDLE_THREAD);
+
     SCHEDULER.schedule();
 
     loop {

kernel/src/scheduler.rs

@@ -1,18 +1,18 @@
 use crate::objects::*;
 use core::ptr::NonNull;
-use log::{error, trace};
+use log::error;
 use spin::lazy::Lazy;
-use utils::linked_list::Link;
+use utils::{container_of, linked_list::Link};
 
 #[thread_local]
-static IDLE_THREAD: Lazy<TcbObject> = Lazy::new(|| {
+pub static IDLE_THREAD: Lazy<TcbObject> = Lazy::new(|| {
     let mut idle_thread = TcbObject::new();
     idle_thread.configure_idle_thread();
     idle_thread
 });
 
 #[thread_local]
-pub static SCHEDULER: Lazy<Scheduler> = Lazy::new(|| Scheduler::new(&IDLE_THREAD));
+pub static SCHEDULER: Scheduler = Scheduler::new();
 
 // TODO: add a shared buffer to transfer TCB between cores
 
@@ -24,14 +24,14 @@ pub struct Scheduler {
 }
 
 impl Scheduler {
-    pub fn new(idle_thread: &TcbObject) -> Self {
+    pub const fn new() -> Self {
-        // link idle_thread
+        Self { head: Link::new() }
-        idle_thread.link.set_prev(Some(NonNull::from(idle_thread)));
-        idle_thread.link.set_next(Some(NonNull::from(idle_thread)));
-
-        Self {
-            head: idle_thread.link.clone(),
     }
+
+    pub fn init(&self) {
+        let head = unsafe { Some(NonNull::from(&*container_of!(&self.head, TcbObject, link))) };
+        self.head.set_next(head);
+        self.head.set_prev(head);
     }
 
     pub fn add(&self, tcb: &TcbObject) {
@@ -41,7 +41,6 @@ impl Scheduler {
     pub fn schedule(&self) {
         while let Some(next) = self.head.next_mut() {
             if next.timetick() > 0 && next.schedulable() {
-                trace!("[Scheduler] Switch to {}, tick: {}", next.tid(), next.timetick());
                 next.activate();
             } else if next.timetick() == 0 {
                 next.set_timetick(TIME_SLICE);