diff --git a/src/kernel/mod.rs b/src/kernel/mod.rs
index e061a2a..f1abafa 100644
--- a/src/kernel/mod.rs
+++ b/src/kernel/mod.rs
@@ -3,4 +3,5 @@ pub mod thread;
 pub mod scheduler;
 pub mod mgerror;
 pub mod system;
-mod ucontext;
\ No newline at end of file
+mod ucontext;
+mod synch;
\ No newline at end of file
diff --git a/src/kernel/synch.rs b/src/kernel/synch.rs
new file mode 100644
index 0000000..a2038e6
--- /dev/null
+++ b/src/kernel/synch.rs
@@ -0,0 +1,43 @@
+use crate::utility::list::List;
+use crate::kernel::thread::Thread;
+use std::rc::Rc;
+use crate::simulator::interrupt::InterruptStatus::InterruptOff;
+use crate::simulator::machine::Machine;
+
+pub struct Semaphore{
+
+    counter:i32,
+    waiting_queue:List<Rc<Thread>>
+
+}
+
+impl Semaphore{
+
+    pub fn p(&mut self, current_thread:Rc<Thread>, machine: &mut Machine){
+        let old_status = machine.interrupt.set_status(InterruptOff);
+        self.counter-=1;
+        if self.counter < 0 {
+            self.waiting_queue.push(Rc::clone(&current_thread));
+            current_thread.sleep();
+        }
+        machine.interrupt.set_status(old_status);
+    }
+
+    pub fn v(&mut self, current_thread:Rc<Thread>, machine: &mut Machine){
+        let old_status = machine.interrupt.set_status(InterruptOff);
+        self.counter-=1;
+        if self.waiting_queue.peek() == None {
+            self.waiting_queue.push(Rc::clone(&current_thread));
+            current_thread.sleep();
+        }
+        machine.interrupt.set_status(old_status);
+    }
+}
+
+pub struct Lock{
+
+}
+
+pub struct Condition{
+
+}
\ No newline at end of file
diff --git a/src/utility/list.rs b/src/utility/list.rs
index 88962c4..024606c 100644
--- a/src/utility/list.rs
+++ b/src/utility/list.rs
@@ -70,6 +70,33 @@ impl<T: PartialEq> List<T> {
         false
     }
 
+    /// Remove the item from the list
+    /// 
+    /// Return true if the item has been found, otherwise return false
+    /// 
+    /// Worst-case complexity is O(n)
+    pub fn remove(&mut self, item: T)-> bool {
+        let mut found = false;
+        let mut tmp_list: List<T> = List::new();
+        while !self.is_empty() {
+            let current = self.pop().unwrap();
+            if current != item {
+                tmp_list.push(current);
+            } else {
+                found = true;
+                break;
+            }
+        }
+        while !tmp_list.is_empty() {
+            self.push(tmp_list.pop().unwrap());
+        }
+        found
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.head.is_none()
+    }
+
     pub fn into_iter(self) -> IntoIter<T> {
         IntoIter(self)
     }