Fix DataReaderThead termination deadlook (#1441)

If realRun is not reaching attach(), the schedule on main thread do
nothing. So we need to introduce a separate bit to avoid such race.

Author: wengxt

src/modules/clipboard/waylandclipboard.cpp

@@ -8,6 +8,7 @@
 #include <unistd.h>
 #include <cstdint>
 #include <memory>
+#include <mutex>
 #include <string>
 #include <string_view>
 #include <unordered_set>
@@ -60,7 +61,14 @@ void DataReaderThread::removeTask(uint64_t token) {
 void DataReaderThread::realRun() {
     EventLoop loop;
     dispatcherToWorker_.attach(&loop);
-    loop.exec();
+    bool terminate = false;
+    {
+        std::lock_guard<std::mutex> lock(mutex_);
+        terminate = terminate_;
+    }
+    if (!terminate) {
+        loop.exec();
+    }
     dispatcherToWorker_.detach();
     FCITX_DEBUG() << "Ending DataReaderThread";
     tasks_.clear();

src/modules/clipboard/waylandclipboard.h

@@ -11,6 +11,7 @@
 #include <functional>
 #include <list>
 #include <memory>
+#include <mutex>
 #include <string>
 #include <thread>
 #include <unordered_map>
@@ -75,6 +76,13 @@ class DataReaderThread {
 
     ~DataReaderThread() {
         if (thread_ && thread_->joinable()) {
+            {
+                std::lock_guard<std::mutex> lock(mutex_);
+                terminate_ = true;
+            }
+            // If dispatcher is not attched, the schedule will do nothing.
+            // But after attach, reader thread will check terminate_
+            // So it won't stuck forever.
             dispatcherToWorker_.schedule([this]() {
                 if (auto *loop = dispatcherToWorker_.eventLoop()) {
                     loop->exit();
@@ -109,6 +117,11 @@ class DataReaderThread {
     std::unique_ptr<std::thread> thread_;
     uint64_t nextId_ = 1;
 
+    // Accessed by both thread
+    std::mutex mutex_;
+    bool terminate_ = false;
+    // End Accessed by both thread
+
     // Value only read/write by the reader thread.
     EventDispatcher dispatcherToWorker_;
     std::unordered_map<uint64_t, DataOfferTask> tasks_;