Implement thread#t_yield()

src/kernel/thread_manager.rs

@@ -52,7 +52,18 @@ impl<'a> ThreadManager<'a> {
     /// 
     /// Cannot use yield as a function name -> reserved name in rust
     pub fn thread_yield(&mut self, thread: Rc<RefCell<Thread>>) {
-        todo!();
+        if let Some(system) = self.system.get() {
+            let mut machine = system.get_g_machine().borrow_mut();
+            let old_status = machine.interrupt.set_status(crate::simulator::interrupt::InterruptStatus::InterruptOff);
+            
+            let next_thread = self.g_scheduler().find_next_to_run();
+            if let Some(next_thread) = next_thread {
+                let scheduler = self.g_scheduler();
+                scheduler.ready_to_run(thread);
+                scheduler.switch_to(system, next_thread);
+            }
+            machine.interrupt.set_status(old_status);
+        }
     }
 
     /// Put the thread to sleep and relinquish the processor
@@ -124,9 +135,4 @@ impl<'a> ThreadManager<'a> {
         self.g_thread_to_be_destroyed = thread
     }
 
-    /// Set Scheduler which will manage the threads
-    pub fn set_g_scheduler(&mut self, scheduler: Scheduler) {
-        self.g_scheduler = scheduler
-    }
-
 }