[kernel] Prevent duplicate defunct enqueue for deleted threads.

include/rtdef.h

@@ -947,6 +947,7 @@ struct rt_thread
 #endif /* RT_USING_MEM_PROTECTION */
 
     struct rt_spinlock          spinlock;
+    rt_uint8_t                  defunct;                /**< cleanup claimed, protected by spinlock */
     rt_ubase_t                  user_data;              /**< private user data beyond this thread */
 };
 typedef struct rt_thread *rt_thread_t;

src/thread.c

@@ -114,6 +114,26 @@ static void _thread_detach_from_mutex(rt_thread_t thread)
 static void _thread_detach_from_mutex(rt_thread_t thread) {}
 #endif
 
+static rt_err_t _thread_mark_defunct(rt_thread_t thread)
+{
+    rt_err_t error = -RT_ERROR;
+    rt_base_t level;
+
+    /*
+     * Scheduler bit-fields use different locking, so this claim has separate
+     * storage. Only thread initialization clears it for a new lifetime.
+     */
+    level = rt_spin_lock_irqsave(&thread->spinlock);
+    if (!thread->defunct)
+    {
+        thread->defunct = RT_TRUE;
+        error = RT_EOK;
+    }
+    rt_spin_unlock_irqrestore(&thread->spinlock, level);
+
+    return error;
+}
+
 static void _thread_exit(void)
 {
     struct rt_thread *thread;
@@ -126,10 +146,13 @@ static void _thread_exit(void)
 
     rt_thread_close(thread);
 
-    _thread_detach_from_mutex(thread);
+    if (_thread_mark_defunct(thread) == RT_EOK)
+    {
+        _thread_detach_from_mutex(thread);
 
-    /* insert to defunct thread list */
-    rt_thread_defunct_enqueue(thread);
+        /* insert to defunct thread list */
+        rt_thread_defunct_enqueue(thread);
+    }
 
     rt_exit_critical_safe(critical_level);
 
@@ -228,6 +251,7 @@ static rt_err_t _thread_init(struct rt_thread *thread,
 
     /* error and flags */
     thread->error = RT_EOK;
+    thread->defunct = RT_FALSE;
 
     /* lock init */
 #ifdef RT_USING_SMP
@@ -513,10 +537,17 @@ static rt_err_t _thread_detach(rt_thread_t thread)
 
     error = rt_thread_close(thread);
 
-    _thread_detach_from_mutex(thread);
+    if (error == RT_EOK)
+    {
+        error = _thread_mark_defunct(thread);
+        if (error == RT_EOK)
+        {
+            _thread_detach_from_mutex(thread);
 
-    /* insert to defunct thread list */
-    rt_thread_defunct_enqueue(thread);
+            /* insert to defunct thread list */
+            rt_thread_defunct_enqueue(thread);
+        }
+    }
 
     rt_exit_critical_safe(critical_level);
     return error;