diff --git a/include/pocketpy/common/threads.h b/include/pocketpy/common/threads.h
index 4be7458b..de988bf4 100644
--- a/include/pocketpy/common/threads.h
+++ b/include/pocketpy/common/threads.h
@@ -44,12 +44,11 @@ void c11_cond__broadcast(c11_cond_t* cond);
 
 typedef void (*c11_thrdpool_func_t)(void* arg);
 
-
 typedef struct c11_thrdpool_tasks {
+    atomic_int sync_val;
     c11_thrdpool_func_t func;
     void** args;
     int length;
-    int sync_val;
     atomic_int current_index;
     atomic_int completed_count;
 } c11_thrdpool_tasks;
@@ -64,10 +63,9 @@ typedef struct c11_thrdpool_worker {
 typedef struct c11_thrdpool {
     int length;
     c11_thrdpool_worker* workers;
-    atomic_bool is_busy;
-    
-    c11_mutex_t workers_mutex[2];
-    c11_cond_t workers_cond[2];
+
+    c11_mutex_t workers_mutex;
+    c11_cond_t workers_cond;
     c11_thrdpool_tasks tasks;
 } c11_thrdpool;
 
diff --git a/src/common/threads.c b/src/common/threads.c
index 2b1e2a73..e76b8362 100644
--- a/src/common/threads.c
+++ b/src/common/threads.c
@@ -71,29 +71,22 @@ void c11_cond__broadcast(c11_cond_t* cond) { cnd_broadcast(cond); }
 
 #endif
 
-static bool _thrdpool_worker_sync(c11_mutex_t* p_mutex,
-                                  c11_cond_t* p_cond,
-                                  int* p_sync_val,
-                                  int expected_sync_val) {
-    int index = (int)expected_sync_val;
-    c11_mutex__lock(p_mutex + index);
-    while(true) {
-        c11_cond__wait(p_cond + index, p_mutex + index);
-        if(*p_sync_val == -1) return false;
-        if(*p_sync_val == expected_sync_val) break;
-    }
-    c11_mutex__unlock(p_mutex + index);
-    return true;
-}
-
 static c11_thrd_retval_t _thrdpool_worker(void* arg) {
     c11_thrdpool_worker* p_worker = (c11_thrdpool_worker*)arg;
     c11_thrdpool_tasks* p_tasks = p_worker->p_tasks;
 
     while(true) {
-        if(!_thrdpool_worker_sync(p_worker->p_mutex, p_worker->p_cond, &p_tasks->sync_val, 0)) {
-            break;
+        c11_mutex__lock(p_worker->p_mutex);
+        while(true) {
+            c11_cond__wait(p_worker->p_cond, p_worker->p_mutex);
+            int sync_val = atomic_load(&p_tasks->sync_val);
+            if(sync_val == -1) {
+                c11_mutex__unlock(p_worker->p_mutex);
+                return 0;  // force kill
+            }
+            if(sync_val == 1) break;
         }
+        c11_mutex__unlock(p_worker->p_mutex);
 
         // execute tasks
         while(true) {
@@ -106,10 +99,6 @@ static c11_thrd_retval_t _thrdpool_worker(void* arg) {
                 break;
             }
         }
-
-        if(!_thrdpool_worker_sync(p_worker->p_mutex, p_worker->p_cond, &p_tasks->sync_val, 1)) {
-            break;
-        }
     }
     return 0;
 }
@@ -117,17 +106,16 @@ static c11_thrd_retval_t _thrdpool_worker(void* arg) {
 void c11_thrdpool__ctor(c11_thrdpool* pool, int length) {
     pool->length = length;
     pool->workers = PK_MALLOC(sizeof(c11_thrdpool_worker) * length);
-    atomic_store(&pool->is_busy, false);
 
-    c11_mutex__ctor(&pool->workers_mutex[0]);
-    c11_mutex__ctor(&pool->workers_mutex[1]);
-    c11_cond__ctor(&pool->workers_cond[0]);
-    c11_cond__ctor(&pool->workers_cond[1]);
+    c11_mutex__ctor(&pool->workers_mutex);
+    c11_cond__ctor(&pool->workers_cond);
+
+    atomic_store(&pool->tasks.sync_val, 0);
 
     for(int i = 0; i < length; i++) {
         c11_thrdpool_worker* p_worker = &pool->workers[i];
-        p_worker->p_mutex = pool->workers_mutex;
-        p_worker->p_cond = pool->workers_cond;
+        p_worker->p_mutex = &pool->workers_mutex;
+        p_worker->p_cond = &pool->workers_cond;
         p_worker->p_tasks = &pool->tasks;
         bool ok = c11_thrd__create(&p_worker->thread, _thrdpool_worker, p_worker);
         c11__rtassert(ok);
@@ -135,14 +123,8 @@ void c11_thrdpool__ctor(c11_thrdpool* pool, int length) {
 }
 
 void c11_thrdpool__dtor(c11_thrdpool* pool) {
-    c11_mutex__lock(&pool->workers_mutex[0]);
-    c11_mutex__lock(&pool->workers_mutex[1]);
-    pool->tasks.sync_val = -1;
-    c11_mutex__unlock(&pool->workers_mutex[1]);
-    c11_mutex__unlock(&pool->workers_mutex[0]);
-    
-    c11_cond__broadcast(&pool->workers_cond[0]);
-    c11_cond__broadcast(&pool->workers_cond[1]);
+    atomic_store(&pool->tasks.sync_val, -1);
+    c11_cond__broadcast(&pool->workers_cond);
 
     for(int i = 0; i < pool->length; i++) {
         c11_thrdpool_worker* p_worker = &pool->workers[i];
@@ -150,40 +132,30 @@ void c11_thrdpool__dtor(c11_thrdpool* pool) {
     }
 
     PK_FREE(pool->workers);
-    c11_mutex__dtor(&pool->workers_mutex[0]);
-    c11_mutex__dtor(&pool->workers_mutex[1]);
-    c11_cond__dtor(&pool->workers_cond[0]);
-    c11_cond__dtor(&pool->workers_cond[1]);
+    c11_mutex__dtor(&pool->workers_mutex);
+    c11_cond__dtor(&pool->workers_cond);
 }
 
 void c11_thrdpool__map(c11_thrdpool* pool, c11_thrdpool_func_t func, void** args, int num_tasks) {
     if(num_tasks == 0) return;
-    bool expected = false;
-    while(!atomic_compare_exchange_weak(&pool->is_busy, &expected, true)) {
-        expected = false;
+    while(atomic_load(&pool->tasks.sync_val) != 0) {
         c11_thrd__yield();
     }
     // assign tasks
-    c11_mutex__lock(&pool->workers_mutex[0]);
+    c11_mutex__lock(&pool->workers_mutex);
     pool->tasks.func = func;
     pool->tasks.args = args;
     pool->tasks.length = num_tasks;
-    pool->tasks.sync_val = 0;
+    atomic_store(&pool->tasks.sync_val, 1);
     atomic_store(&pool->tasks.current_index, 0);
     atomic_store(&pool->tasks.completed_count, 0);
-    c11_cond__broadcast(&pool->workers_cond[0]);
-    c11_mutex__unlock(&pool->workers_mutex[0]);
+    c11_cond__broadcast(&pool->workers_cond);
+    c11_mutex__unlock(&pool->workers_mutex);
     // wait for complete
     while(atomic_load(&pool->tasks.completed_count) < num_tasks) {
         c11_thrd__yield();
     }
-    // notify workers to proceed
-    c11_mutex__lock(&pool->workers_mutex[1]);
-    pool->tasks.sync_val = 1;
-    c11_cond__broadcast(&pool->workers_cond[1]);
-    c11_mutex__unlock(&pool->workers_mutex[1]);
-    // mark as not busy
-    atomic_store(&pool->is_busy, false);
+    atomic_store(&pool->tasks.sync_val, 0);
 }
 
 #endif  // PK_ENABLE_THREADS
\ No newline at end of file