diff --git a/src/threadpoolman.cpp b/src/threadpoolman.cpp
index ebce944..db4f47d 100644
--- a/src/threadpoolman.cpp
+++ b/src/threadpoolman.cpp
@@ -75,11 +75,11 @@ void* ThreadPoolMan::Worker(void* arg)
     }
     S3FS_PRN_INFO3("Start worker thread in ThreadPoolMan.");
 
-    while(!psingleton->is_exit){
+    while(!psingleton->IsExit()){
         // wait
         psingleton->thpoolman_sem.wait();
 
-        if(psingleton->is_exit){
+        if(psingleton->IsExit()){
             break;
         }
 
@@ -119,7 +119,7 @@ void* ThreadPoolMan::Worker(void* arg)
 //------------------------------------------------
 // ThreadPoolMan methods
 //------------------------------------------------
-ThreadPoolMan::ThreadPoolMan(int count) : is_exit(false), thpoolman_sem(0)
+ThreadPoolMan::ThreadPoolMan(int count) : is_exit(false), thpoolman_sem(0), is_lock_init(false), is_exit_flag_init(false)
 {
     if(count < 1){
         S3FS_PRN_CRIT("Failed to creating singleton for Thread Manager, because thread count(%d) is under 1.", count);
@@ -130,12 +130,12 @@ ThreadPoolMan::ThreadPoolMan(int count) : is_exit(false), thpoolman_sem(0)
         abort();
     }
 
-    is_lock_init = false;
     pthread_mutexattr_t attr;
     pthread_mutexattr_init(&attr);
 #if S3FS_PTHREAD_ERRORCHECK
     pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK);
 #endif
+
     int result;
     if(0 != (result = pthread_mutex_init(&thread_list_lock, &attr))){
         S3FS_PRN_CRIT("failed to init thread_list_lock: %d", result);
@@ -143,6 +143,12 @@ ThreadPoolMan::ThreadPoolMan(int count) : is_exit(false), thpoolman_sem(0)
     }
     is_lock_init = true;
 
+    if(0 != (result = pthread_mutex_init(&thread_exit_flag_lock, &attr))){
+        S3FS_PRN_CRIT("failed to init thread_exit_flag_lock: %d", result);
+        abort();
+    }
+    is_exit_flag_init = true;
+
     // create threads
     if(!StartThreads(count)){
         S3FS_PRN_ERR("Failed starting threads at initializing.");
@@ -155,13 +161,33 @@ ThreadPoolMan::~ThreadPoolMan()
     StopThreads();
 
     if(is_lock_init){
-      int result;
-      if(0 != (result = pthread_mutex_destroy(&thread_list_lock))){
-          S3FS_PRN_CRIT("failed to destroy thread_list_lock: %d", result);
-          abort();
-      }
-      is_lock_init = false;
+        int result;
+        if(0 != (result = pthread_mutex_destroy(&thread_list_lock))){
+            S3FS_PRN_CRIT("failed to destroy thread_list_lock: %d", result);
+            abort();
+        }
+        is_lock_init = false;
     }
+    if(is_exit_flag_init ){
+        int result;
+        if(0 != (result = pthread_mutex_destroy(&thread_exit_flag_lock))){
+            S3FS_PRN_CRIT("failed to destroy thread_exit_flag_lock: %d", result);
+            abort();
+        }
+        is_exit_flag_init  = false;
+    }
+}
+
+bool ThreadPoolMan::IsExit()
+{
+    AutoLock auto_lock(&thread_exit_flag_lock);
+    return is_exit;
+}
+
+void ThreadPoolMan::SetExitFlag(bool exit_flag)
+{
+    AutoLock auto_lock(&thread_exit_flag_lock);
+    is_exit = exit_flag;
 }
 
 bool ThreadPoolMan::StopThreads()
@@ -172,7 +198,7 @@ bool ThreadPoolMan::StopThreads()
     }
 
     // all threads to exit
-    is_exit = true;
+    SetExitFlag(true);
     for(uint waitcnt = thread_list.size(); 0 < waitcnt; --waitcnt){
         thpoolman_sem.post();
     }
@@ -216,7 +242,7 @@ bool ThreadPoolMan::StartThreads(int count)
     }
 
     // create all threads
-    is_exit = false;
+    SetExitFlag(false);
     for(int cnt = 0; cnt < count; ++cnt){
         // run thread
         pthread_t thread;
diff --git a/src/threadpoolman.h b/src/threadpoolman.h
index 5066532..fdd3a3d 100644
--- a/src/threadpoolman.h
+++ b/src/threadpoolman.h
@@ -60,7 +60,7 @@ class ThreadPoolMan
     private:
         static ThreadPoolMan* singleton;
 
-        volatile bool         is_exit;
+        bool                  is_exit;
         Semaphore             thpoolman_sem;
 
         bool                  is_lock_init;
@@ -69,12 +69,18 @@ class ThreadPoolMan
 
         thpoolman_params_t    instruction_list;
 
+        bool                  is_exit_flag_init;
+        pthread_mutex_t       thread_exit_flag_lock;
+
     private:
         static void* Worker(void* arg);
 
         explicit ThreadPoolMan(int count = 1);
         ~ThreadPoolMan();
 
+        bool IsExit();
+        void SetExitFlag(bool exit_flag);
+
         bool StopThreads();
         bool StartThreads(int count);
         bool SetInstruction(thpoolman_param* pparam);