diff --git a/source/module/monitor_kernel.h b/source/module/monitor_kernel.h
index dda9108..de394c7 100644
--- a/source/module/monitor_kernel.h
+++ b/source/module/monitor_kernel.h
@@ -11,3 +11,5 @@ void monitor_exit(void);
 
 int start_watch_variable(watch_arg warg);
 void clear_watch(pid_t pid);
+
+enum hrtimer_restart check_variable_cb(struct hrtimer *timer);  // callback
diff --git a/source/module/monitor_kernel_lib.c b/source/module/monitor_kernel_lib.c
index b2b0260..6c42005 100644
--- a/source/module/monitor_kernel_lib.c
+++ b/source/module/monitor_kernel_lib.c
@@ -127,4 +127,56 @@ void clear_watch(pid_t pid) {
   del_all_kwarg_by_pid(pid);  // delete all kwarg with pid
   free_page_list(pid);        // free page with pid
   start_all_hrTimer();        // restart timer
+}
+
+/**
+ * @brief main callback function
+ *
+ * @param timer
+ * @return enum hrtimer_restart
+ */
+enum hrtimer_restart check_variable_cb(struct hrtimer *timer) {
+  kernel_watch_timer *k_watch_timer =
+      container_of(timer, kernel_watch_timer, hr_timer);
+  int i = 0, j = 0;
+  int buffer[TIMER_MAX_WATCH_NUM];  // Buffer to store the messages
+
+  // // check all watched kernel_watch_arg
+  // for (i = 0; i < k_watch_timer->sentinel; i++) {
+  //   if (read_and_compare(&k_watch_timer->k_watch_args[i])) {
+  //     // snprintf(buffer + strlen(buffer), sizeof(buffer) - strlen(buffer), "
+  //     // name: %s, threshold: %lld, pid: %d\n",
+  //     //          k_watch_timer->k_watch_args[i].name,
+  //     //          k_watch_timer->k_watch_args[i].threshold,
+  //     //          k_watch_timer->k_watch_args[i].task_id);
+  //     buffer[j] = i;
+  //     j++;
+
+  //     // printk(KERN_INFO "j: name %s, threshold: %lld\n",
+  //     // k_watch_timer->k_watch_args[i].name,
+  //     //        k_watch_timer->k_watch_args[i].threshold);
+  //     // printk(KERN_INFO "j: %d\n", j);
+  //   }
+  // }
+  if (j > 0)  // if any threshold reached
+  {
+    printk("-------------------------------------\n");
+    printk("-------------watch monitor-----------\n");
+    printk("Threshold reached:\n");
+
+    for (i = 0; i < j; i++) {
+      printk(" name: %s, threshold: %lld, pid: %d\n",
+             k_watch_timer->k_watch_args[buffer[i]].name,  //! todo
+             k_watch_timer->k_watch_args[buffer[i]].threshold,
+             k_watch_timer->k_watch_args[buffer[i]].task_id);
+    }
+    // print_task_stack();
+    // restart timer after 1s
+    hrtimer_forward(timer, timer->base->get_time(), ktime_set(1, 0));  //! todo
+    printk("-------------------------------------\n");
+  } else {
+    // keep frequency
+    hrtimer_forward(timer, timer->base->get_time(), k_watch_timer->kt);
+  }
+  return HRTIMER_RESTART;  // restart timer
 }
\ No newline at end of file
diff --git a/source/module/monitor_timer.c b/source/module/monitor_timer.c
index 2bef95d..dbc57ea 100644
--- a/source/module/monitor_timer.c
+++ b/source/module/monitor_timer.c
@@ -115,53 +115,6 @@ unsigned char timer_del_watch_by_pid(kernel_watch_timer *timer, pid_t pid) {
   return 0;
 }
 
-/// @brief hrTimer handler
-enum hrtimer_restart check_variable_cb(struct hrtimer *timer) {
-  kernel_watch_timer *k_watch_timer =
-      container_of(timer, kernel_watch_timer, hr_timer);
-  int i = 0, j = 0;
-  int buffer[TIMER_MAX_WATCH_NUM]; // Buffer to store the messages
-
-  // // check all watched kernel_watch_arg
-  // for (i = 0; i < k_watch_timer->sentinel; i++) {
-  //   if (read_and_compare(&k_watch_timer->k_watch_args[i])) {
-  //     // snprintf(buffer + strlen(buffer), sizeof(buffer) - strlen(buffer), "
-  //     // name: %s, threshold: %lld, pid: %d\n",
-  //     //          k_watch_timer->k_watch_args[i].name,
-  //     //          k_watch_timer->k_watch_args[i].threshold,
-  //     //          k_watch_timer->k_watch_args[i].task_id);
-  //     buffer[j] = i;
-  //     j++;
-
-  //     // printk(KERN_INFO "j: name %s, threshold: %lld\n",
-  //     // k_watch_timer->k_watch_args[i].name,
-  //     //        k_watch_timer->k_watch_args[i].threshold);
-  //     // printk(KERN_INFO "j: %d\n", j);
-  //   }
-  // }
-  if (j > 0) // if any threshold reached
-  {
-    printk("-------------------------------------\n");
-    printk("-------------watch monitor-----------\n");
-    printk("Threshold reached:\n");
-
-    for (i = 0; i < j; i++) {
-      printk(" name: %s, threshold: %lld, pid: %d\n",
-             k_watch_timer->k_watch_args[buffer[i]].name, //! todo
-             k_watch_timer->k_watch_args[buffer[i]].threshold,
-             k_watch_timer->k_watch_args[buffer[i]].task_id);
-    }
-    // print_task_stack();
-    // restart timer after 1s
-    hrtimer_forward(timer, timer->base->get_time(), ktime_set(1, 0)); //! todo
-    printk("-------------------------------------\n");
-  } else {
-    // keep frequency
-    hrtimer_forward(timer, timer->base->get_time(), k_watch_timer->kt);
-  }
-  return HRTIMER_RESTART; // restart timer
-}
-
 /// @brief start hrTimer
 /// @param timeout: timeout in us
 /// @return 0 is success
diff --git a/source/module/monitor_timer.h b/source/module/monitor_timer.h
index 2367dcc..0feb57c 100644
--- a/source/module/monitor_timer.h
+++ b/source/module/monitor_timer.h
@@ -54,6 +54,6 @@ unsigned char timer_add_watch(kernel_watch_timer *timer,
                               kernel_watch_arg k_watch_arg);
 unsigned char timer_del_watch_by_pid(kernel_watch_timer *timer, pid_t pid);
 
-enum hrtimer_restart check_variable_cb(struct hrtimer *timer); // callback
+extern enum hrtimer_restart check_variable_cb(struct hrtimer *timer); // callback
 void start_all_hrTimer(void);
 void cancel_all_hrTimer(void);
\ No newline at end of file