thread-value: Defer cleanup handling to thread termination on Windows

Instead of cleaning up all thread-values during destruction, cleanup handler
is invoked when a thread detaches. Thread detaching is cough using the Windows
DllMain() entry point, and allows us to basically revert 204098a7.

Using this mechanism, we make sure that the cleanup handler is invoked by the
the correct thread. Further, this mechanism works for externally-spawned
threads which run outside of our thread_cb() routine, and works more efficiently
with short-running threads.

src/libstrongswan/threading/windows/thread.c

@@ -245,36 +245,6 @@ void* thread_tls_remove(void *key)
 	return value;
 }
 
-/**
- * See header.
- */
-void thread_tls_remove_all(void *key)
-{
-	private_thread_t *thread;
-	enumerator_t *enumerator;
-	void *value;
-	bool old;
-
-	old = set_leak_detective(FALSE);
-	threads_lock->lock(threads_lock);
-
-	enumerator = threads->create_enumerator(threads);
-	while (enumerator->enumerate(enumerator, NULL, &thread))
-	{
-		value = thread->tls->remove(thread->tls, key);
-		if (value)
-		{
-			set_leak_detective(old);
-			thread_tls_cleanup(value);
-			set_leak_detective(FALSE);
-		}
-	}
-	enumerator->destroy(enumerator);
-
-	threads_lock->unlock(threads_lock);
-	set_leak_detective(old);
-}
-
 /**
  * Thread cleanup data
  */
@@ -634,6 +604,50 @@ void thread_exit(void *val)
 	ExitThread(0);
 }
 
+/**
+ * Clean up thread data while it detaches
+ */
+static void cleanup_tls()
+{
+	private_thread_t *this;
+	bool old;
+
+	old = set_leak_detective(FALSE);
+	threads_lock->lock(threads_lock);
+
+	this = threads->remove(threads, (void*)(uintptr_t)GetCurrentThreadId());
+
+	threads_lock->unlock(threads_lock);
+	set_leak_detective(old);
+
+	if (this)
+	{
+		/* If the thread exited, but has not been joined, it is in terminated
+		 * state. We must not mangle it, as we target externally spawned
+		 * threads only. */
+		if (!this->terminated && !this->detached)
+		{
+			destroy(this);
+		}
+	}
+}
+
+/**
+ * DllMain called for dll events
+ */
+BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved)
+{
+	switch (fdwReason)
+	{
+		case DLL_THREAD_DETACH:
+			cleanup_tls();
+			break;
+		default:
+			break;
+	}
+	return TRUE;
+}
+
 /*
  * Described in header.
  */