diff --git a/src/kernel/synch.rs b/src/kernel/synch.rs
index e7b9ac2..d7257be 100644
--- a/src/kernel/synch.rs
+++ b/src/kernel/synch.rs
@@ -1,3 +1,4 @@
+use core::panicking::panic;
 use crate::utility::list::List;
 use crate::kernel::thread::Thread;
 use crate::simulator::interrupt::InterruptStatus::InterruptOff;
@@ -23,6 +24,10 @@ pub struct Semaphore {
 
 impl Semaphore {
 
+    pub fn new(counter: i32, thread_manager: Rc<RefCell<ThreadManager>>) -> Semaphore{
+        Semaphore { counter, waiting_queue: List::new(), thread_manager}
+    }
+
     ///     Decrement the value, and wait if it becomes < 0. Checking the
     ///	value and decrementing must be done atomically, so we
     ///	need to disable interrupts before checking the value.
@@ -69,7 +74,7 @@ impl Semaphore {
 pub struct Lock{
 
     /// Thread owning the lock
-    owner: Rc<RefCell<Thread>>,
+    owner: Option<Rc<RefCell<Thread>>>,
     /// The queue of threads waiting for execution
     waiting_queue:List<Rc<RefCell<Thread>>>,
     /// Thread manager which managing threads
@@ -81,6 +86,15 @@ pub struct Lock{
 
 impl Lock {
 
+    ///    Initialize a Lock, so that it can be used for synchronization.
+    /// The lock is initialy free
+    ///
+    /// ### Parameters
+    /// - **thread_manager** Thread manager which managing threads
+    pub fn new(thread_manager: Rc<RefCell<ThreadManager>>) -> Lock {
+        Lock { owner: None, waiting_queue: List::new(), thread_manager, free: true }
+    }
+
     ///    Wait until the lock become free.  Checking the
     ///	state of the lock (free or busy) and modify it must be done
     ///	atomically, so we need to disable interrupts before checking
@@ -92,15 +106,20 @@ impl Lock {
     /// ### Parameters
     /// - **current_thread** the current thread
     /// - **machine** the machine where the threads are executed
-    pub fn acquire(&mut self, current_thread: Rc<RefCell<Thread>>, machine: &mut Machine) {
+    pub fn acquire(&mut self, current_thread: Option<Rc<RefCell<Thread>>>, machine: &mut Machine) {
         let old_status = machine.interrupt.set_status(InterruptOff);
 
         if self.free {
             self.free = false;
             self.owner = current_thread;
         } else {
-            self.waiting_queue.push(Rc::clone(&current_thread));
-            self.thread_manager.borrow_mut().thread_sleep(current_thread);
+            match current_thread {
+                Some(x) => {
+                    self.waiting_queue.push(Rc::clone(&x));
+                    self.thread_manager.borrow_mut().thread_sleep(x)
+                },
+                None => ()
+            }
         }
 
         machine.interrupt.set_status(old_status);
@@ -120,8 +139,11 @@ impl Lock {
 
         if self.held_by_current_thread(current_thread) {
             if self.waiting_queue.peek() != None {
-                self.owner = self.waiting_queue.pop().unwrap();
-                scheduler.ready_to_run(Rc::clone(&self.owner));
+                self.owner = Some(self.waiting_queue.pop().unwrap());
+                match &self.owner {
+                    Some(x) => scheduler.ready_to_run(Rc::clone(&x)),
+                    None => ()
+                }
             } else {
                 self.free = true;
             }
@@ -147,6 +169,14 @@ pub struct Condition{
 
 impl Condition {
 
+    /// Initializes a Condition, so that it can be used for synchronization.
+    ///
+    /// ### Parameters
+    /// - *thread_manager* Thread manager which managing threads
+    pub fn new(thread_manager: Rc<RefCell<ThreadManager>>) -> Condition {
+        Condition{ waiting_queue: List::new(), thread_manager }
+    }
+
     ///  Block the calling thread (put it in the wait queue).
     ///  This operation must be atomic, so we need to disable interrupts.
     ///