diff --git a/os/src/syscall/mod.rs b/os/src/syscall/mod.rs
index fa4a4cf1..ca3fc526 100644
--- a/os/src/syscall/mod.rs
+++ b/os/src/syscall/mod.rs
@@ -62,7 +62,7 @@ pub fn syscall(syscall_id: usize, args: [usize; 3]) -> isize {
         SYSCALL_SEMAPHORE_CREATE => sys_semaphore_create(args[0]),
         SYSCALL_SEMAPHORE_UP => sys_semaphore_up(args[0]),
         SYSCALL_SEMAPHORE_DOWN => sys_semaphore_down(args[0]),
-        SYSCALL_CONDVAR_CREATE => sys_condvar_create(args[0]),
+        SYSCALL_CONDVAR_CREATE => sys_condvar_create(),
         SYSCALL_CONDVAR_SIGNAL => sys_condvar_signal(args[0]),
         SYSCALL_CONDVAR_WAIT => sys_condvar_wait(args[0], args[1]),
         _ => panic!("Unsupported syscall_id: {}", syscall_id),
diff --git a/os/src/syscall/sync.rs b/os/src/syscall/sync.rs
index dd0e856a..eb67583a 100644
--- a/os/src/syscall/sync.rs
+++ b/os/src/syscall/sync.rs
@@ -93,7 +93,7 @@ pub fn sys_semaphore_down(sem_id: usize) -> isize {
     0
 }
 
-pub fn sys_condvar_create(_arg: usize) -> isize {
+pub fn sys_condvar_create() -> isize {
     let process = current_process();
     let mut process_inner = process.inner_exclusive_access();
     let id = if let Some(id) = process_inner
diff --git a/user/src/bin/barrier_condvar.rs b/user/src/bin/barrier_condvar.rs
index db0a80ba..ca0953b3 100644
--- a/user/src/bin/barrier_condvar.rs
+++ b/user/src/bin/barrier_condvar.rs
@@ -28,7 +28,7 @@ impl Barrier {
     }
     pub fn block(&self) {
         mutex_lock(self.mutex_id);
-        let mut count = self.count.get();
+        let count = self.count.get();
         // SAFETY: Here, the accesses of the count is in the
         // critical section protected by the mutex.
         unsafe { *count = *count + 1; } 
diff --git a/user/src/bin/test_condvar.rs b/user/src/bin/condsync_condvar.rs
similarity index 100%
rename from user/src/bin/test_condvar.rs
rename to user/src/bin/condsync_condvar.rs
index 2db9d8a4..b83aeda2 100644
--- a/user/src/bin/test_condvar.rs
+++ b/user/src/bin/condsync_condvar.rs
@@ -35,8 +35,8 @@ unsafe fn second() -> ! {
         println!("Second: A is {}", A);
         condvar_wait(CONDVAR_ID, MUTEX_ID);
     }
-    mutex_unlock(MUTEX_ID);
     println!("A is {}, Second can work now", A);
+    mutex_unlock(MUTEX_ID);
     exit(0)
 }
 
diff --git a/user/src/bin/condsync_sem.rs b/user/src/bin/condsync_sem.rs
new file mode 100644
index 00000000..d7b875a7
--- /dev/null
+++ b/user/src/bin/condsync_sem.rs
@@ -0,0 +1,64 @@
+#![no_std]
+#![no_main]
+
+#[macro_use]
+extern crate user_lib;
+
+extern crate alloc;
+
+use alloc::vec;
+use user_lib::exit;
+use user_lib::{
+    semaphore_create, semaphore_down, semaphore_up, mutex_blocking_create, mutex_lock, mutex_unlock,
+};
+use user_lib::{sleep, thread_create, waittid};
+
+static mut A: usize = 0;
+
+const SEM_ID: usize = 0;
+const MUTEX_ID: usize = 0;
+
+unsafe fn first() -> ! {
+    sleep(10);
+    println!("First work, Change A --> 1 and wakeup Second");
+    mutex_lock(MUTEX_ID);
+    A = 1;
+    semaphore_up(SEM_ID);
+    mutex_unlock(MUTEX_ID);
+    exit(0)
+}
+
+unsafe fn second() -> ! {
+    println!("Second want to continue,but need to wait A=1");
+    loop {
+        mutex_lock(MUTEX_ID);
+        if A == 0 {
+            println!("Second: A is {}", A);
+            mutex_unlock(MUTEX_ID);
+            semaphore_down(SEM_ID);
+        } else {
+            mutex_unlock(MUTEX_ID);
+            break;
+        }
+    }
+    println!("A is {}, Second can work now", A);
+    exit(0)
+}
+
+#[no_mangle]
+pub fn main() -> i32 {
+    // create semaphore & mutex
+    assert_eq!(semaphore_create(0) as usize, SEM_ID);
+    assert_eq!(mutex_blocking_create() as usize, MUTEX_ID);
+    // create threads
+    let threads = vec![
+        thread_create(first as usize, 0),
+        thread_create(second as usize, 0),
+    ];
+    // wait for all threads to complete
+    for thread in threads.iter() {
+        waittid(*thread as usize);
+    }
+    println!("test_condvar passed!");
+    0
+}
diff --git a/user/src/lib.rs b/user/src/lib.rs
index 3677a65d..7e5482ae 100644
--- a/user/src/lib.rs
+++ b/user/src/lib.rs
@@ -189,7 +189,7 @@ pub fn semaphore_down(sem_id: usize) {
     sys_semaphore_down(sem_id);
 }
 pub fn condvar_create() -> isize {
-    sys_condvar_create(0)
+    sys_condvar_create()
 }
 pub fn condvar_signal(condvar_id: usize) {
     sys_condvar_signal(condvar_id);
diff --git a/user/src/syscall.rs b/user/src/syscall.rs
index 4cd714ef..eecdf096 100644
--- a/user/src/syscall.rs
+++ b/user/src/syscall.rs
@@ -145,8 +145,8 @@ pub fn sys_semaphore_down(sem_id: usize) -> isize {
     syscall(SYSCALL_SEMAPHORE_DOWN, [sem_id, 0, 0])
 }
 
-pub fn sys_condvar_create(_arg: usize) -> isize {
-    syscall(SYSCALL_CONDVAR_CREATE, [_arg, 0, 0])
+pub fn sys_condvar_create() -> isize {
+    syscall(SYSCALL_CONDVAR_CREATE, [0, 0, 0])
 }
 
 pub fn sys_condvar_signal(condvar_id: usize) -> isize {