From fe519555cc7d7147f98017389f0886b0183e3df9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois=20Autin?=
 <francois.autin@etudiant.univ-rennes1.fr>
Date: Wed, 19 Apr 2023 23:33:37 +0200
Subject: [PATCH] Removed thread_to_be_destroyed field and associated methods

This used to exist in NachOS' source code as memory management is manual in C++.
Here, simply dropping the Thread from the thread list allows the borrow checker to
automatically destroy the thread.
---
 src/kernel/thread_manager.rs | 55 ++++++++++++++++++------------------
 1 file changed, 27 insertions(+), 28 deletions(-)

diff --git a/src/kernel/thread_manager.rs b/src/kernel/thread_manager.rs
index da4518e..eb69172 100644
--- a/src/kernel/thread_manager.rs
+++ b/src/kernel/thread_manager.rs
@@ -1,11 +1,31 @@
-use std::{rc::Rc, cell::{RefCell, Ref}, fmt::format};
+use std::{
+    rc::Rc,
+    cell::{
+        RefCell,
+        Ref
+    }
+};
 
-use crate::{utility::{list::List, objaddr::ObjAddr}, simulator::{machine::{NUM_INT_REGS, NUM_FP_REGS, Machine}, interrupt::InterruptStatus, error::{MachineOk, MachineError}}};
+use crate::{
+    utility::{
+        list::List,
+        objaddr::ObjAddr
+    },
+    simulator::{
+        machine::{
+            NUM_INT_REGS,
+            NUM_FP_REGS,
+            Machine
+        },
+        interrupt::InterruptStatus,
+        error::{
+            MachineOk,
+            MachineError
+        }
+    }
+};
 
 use super::{thread::Thread, process::Process};
-
-pub const SIMULATORSTACKSIZE: usize = 32 * 1024;
-
 /// # Thread manager
 /// 
 /// An instance of this struct is responsible for managing threads on behalf of the system
@@ -13,8 +33,6 @@ pub const SIMULATORSTACKSIZE: usize = 32 * 1024;
 pub struct ThreadManager {
     /// Current running thread
     pub g_current_thread: Option<Rc<RefCell<Thread>>>,
-    /// The thread to be destroyed next
-    pub g_thread_to_be_destroyed: Option<Rc<RefCell<Thread>>>,
     /// The list of alive threads
     pub g_alive: List<Rc<RefCell<Thread>>>,
     /// Thread in ready state waiting to become active
@@ -28,8 +46,7 @@ impl ThreadManager {
     /// Thread manager constructor
     pub fn new(debug: bool) -> Self {
         Self { 
-            g_current_thread: Option::None, 
-            g_thread_to_be_destroyed: Option::None, 
+            g_current_thread: Option::None,
             g_alive: List::default(),
             ready_list: List::default(),
             obj_addrs: ObjAddr::init(),
@@ -85,11 +102,6 @@ impl ThreadManager {
             // next_thread.restore_simulator_state();
             self.set_g_current_thread(Some(next_thread));
         }
-
-        if let Some(th) = self.get_g_thread_to_be_destroyed() {
-            drop(th);
-            self.g_thread_to_be_destroyed = None
-        }
     }
 
     /// Start a thread, attaching it to a process
@@ -147,8 +159,7 @@ impl ThreadManager {
     /// Finish the execution of the thread and prepare its deallocation
     pub fn thread_finish(&mut self, machine: &mut Machine, thread: Rc<RefCell<Thread>>) {
         let old_status = machine.interrupt.set_status(InterruptStatus::InterruptOff);
-        self.set_g_thread_to_be_destroyed(Option::Some(Rc::clone(&thread)));
-        self.g_alive.remove(Rc::clone(&thread));
+        assert_eq!(self.g_alive.remove(Rc::clone(&thread)), true);
         self.debug(format!("Sleeping thread {}", thread.borrow().get_name()));
         // g_objets_addrs->removeObject(self.thread) // a ajouté plus tard
         self.thread_sleep(machine, Rc::clone(&thread));
@@ -296,13 +307,6 @@ impl ThreadManager {
         &self.g_current_thread
     }
 
-    /// Thread to be destroyed by [...]
-    /// 
-    /// TODO: Finish the comment with the relevant value
-    pub fn get_g_thread_to_be_destroyed(&mut self) -> &Option<Rc<RefCell<Thread>>> {
-        &self.g_thread_to_be_destroyed
-    }
-
     /// List of alive threads
     pub fn get_g_alive(&mut self) -> &mut List<Rc<RefCell<Thread>>> {
         &mut self.g_alive
@@ -313,11 +317,6 @@ impl ThreadManager {
         self.g_current_thread = thread
     }
 
-    /// Set thread to be destroyed next
-    pub fn set_g_thread_to_be_destroyed(&mut self, thread: Option<Rc<RefCell<Thread>>>) {
-        self.g_thread_to_be_destroyed = thread
-    }
-
     pub fn get_obj_addrs(&mut self) -> &mut ObjAddr {
         &mut self.obj_addrs 
     }