diff --git a/components/lwp/lwp.h b/components/lwp/lwp.h
index c504ef60ad1..060e9ff34cf 100644
--- a/components/lwp/lwp.h
+++ b/components/lwp/lwp.h
@@ -249,7 +249,7 @@ void lwp_user_setting_restore(rt_thread_t thread);
 void lwp_uthread_ctx_save(void *ctx);
 void lwp_uthread_ctx_restore(void);
 
-int lwp_setaffinity(pid_t pid, int cpu);
+int lwp_setaffinity(int tid, int cpu);
 
 pid_t exec(char *filename, int debug, int argc, char **argv);
 
diff --git a/components/lwp/lwp_pid.c b/components/lwp/lwp_pid.c
index 63a635d2f55..8b149dd5427 100644
--- a/components/lwp/lwp_pid.c
+++ b/components/lwp/lwp_pid.c
@@ -1600,35 +1600,25 @@ static void _resr_cleanup(struct rt_lwp *lwp)
     }
 }
 
-static int _lwp_setaffinity(pid_t pid, int cpu)
+static int _lwp_setaffinity(int tid, int cpu)
 {
-    struct rt_lwp *lwp;
+    rt_thread_t thread;
     int ret = -1;
 
-    lwp_pid_lock_take();
-    lwp = lwp_from_pid_locked(pid);
+    thread = lwp_tid_get_thread_and_inc_ref(tid);
 
-    if (lwp)
+    if (thread)
     {
 #ifdef RT_USING_SMP
-        rt_list_t *list;
-
-        lwp->bind_cpu = cpu;
-        for (list = lwp->t_grp.next; list != &lwp->t_grp; list = list->next)
-        {
-            rt_thread_t thread;
-
-            thread = rt_list_entry(list, struct rt_thread, sibling);
-            rt_thread_control(thread, RT_THREAD_CTRL_BIND_CPU, (void *)(rt_size_t)cpu);
-        }
+        rt_thread_control(thread, RT_THREAD_CTRL_BIND_CPU, (void *)(rt_ubase_t)cpu);
 #endif
         ret = 0;
     }
-    lwp_pid_lock_release();
+    lwp_tid_dec_ref(thread);
     return ret;
 }
 
-int lwp_setaffinity(pid_t pid, int cpu)
+int lwp_setaffinity(int tid, int cpu)
 {
     int ret;
 
@@ -1638,7 +1628,7 @@ int lwp_setaffinity(pid_t pid, int cpu)
         cpu = RT_CPUS_NR;
     }
 #endif
-    ret = _lwp_setaffinity(pid, cpu);
+    ret = _lwp_setaffinity(tid, cpu);
     return ret;
 }
 
diff --git a/components/lwp/lwp_syscall.c b/components/lwp/lwp_syscall.c
index f7fe959eab3..27285e34c5c 100644
--- a/components/lwp/lwp_syscall.c
+++ b/components/lwp/lwp_syscall.c
@@ -5426,6 +5426,12 @@ sysret_t sys_sched_setaffinity(pid_t pid, size_t size, void *set)
         if (CPU_ISSET_S(i, size, kset))
         {
             kmem_put(kset);
+
+            /**
+             * yes it's tricky.
+             * But when we talk about 'pid' from GNU libc, it's the 'task-id'
+             * aka 'thread->tid' known in kernel.
+             */
             return lwp_setaffinity(pid, i);
         }
     }