diff --git a/kernel/src/ipc/semary.rs b/kernel/src/ipc/semary.rs
index 6770bf8c..178b2f61 100644
--- a/kernel/src/ipc/semary.rs
+++ b/kernel/src/ipc/semary.rs
@@ -61,7 +61,8 @@ pub fn new_semary(key: usize, nsems: usize, semflg: usize) -> Arc<SemArray> {
     let mut key2sem_table = KEY2SEM.write();
     let mut sem_array_ref: Arc<SemArray>;
 
-    if key2sem_table.get(&key).is_none() {
+    let mut key_sem_array_ref = key2sem_table.get(&key);
+    if (key_sem_array_ref.is_none() || key_sem_array_ref.unwrap().upgrade().is_none()) {
         let mut semaphores: Vec<Semaphore> = Vec::new();
         for i in 0..nsems {
             semaphores.push(Semaphore::new(0));
diff --git a/user b/user
index 11baf015..746114ac 160000
--- a/user
+++ b/user
@@ -1 +1 @@
-Subproject commit 11baf01577e0ca87ef88e6f1f95d2192e43e5d58
+Subproject commit 746114ac65b255ba7bdffba0445a162e767e0a6f