Fix mutex lock issues (OCR and FR)

modules/ANSOCR/ANSONNXOCR/PaddleOCRV5Engine.h

@@ -7,6 +7,9 @@
 
 #include <memory>
 #include <mutex>
+#include <atomic>
+#include <chrono>
+#include <thread>
 #include <string>
 #include <vector>
 
@@ -48,6 +51,37 @@ private:
     std::unique_ptr<ONNXOCRRecognizer>  recognizer_;
 
     std::recursive_mutex _mutex;
+    std::atomic<bool>    _modelLoading{ false };
+
+    // RAII helper: sets _modelLoading=true on construction, false on destruction.
+    struct ModelLoadingGuard {
+        std::atomic<bool>& flag;
+        explicit ModelLoadingGuard(std::atomic<bool>& f) : flag(f) { flag.store(true); }
+        ~ModelLoadingGuard() { flag.store(false); }
+        ModelLoadingGuard(const ModelLoadingGuard&) = delete;
+        ModelLoadingGuard& operator=(const ModelLoadingGuard&) = delete;
+    };
+
+    // Try to lock _mutex with a timeout.  Returns a unique_lock that
+    // evaluates to true on success.
+    std::unique_lock<std::recursive_mutex> TryLockWithTimeout(
+            const char* caller, unsigned int timeoutMs = 5000)
+    {
+        const auto deadline = std::chrono::steady_clock::now()
+                            + std::chrono::milliseconds(timeoutMs);
+        std::unique_lock<std::recursive_mutex> lk(_mutex, std::defer_lock);
+        while (!lk.try_lock()) {
+            if (std::chrono::steady_clock::now() >= deadline) {
+                std::cerr << "[" << caller << "] Mutex acquisition timed out after "
+                          << timeoutMs << " ms"
+                          << (_modelLoading.load() ? " (model loading in progress)" : "")
+                          << std::endl;
+                return lk; // unlocked
+            }
+            std::this_thread::sleep_for(std::chrono::milliseconds(1));
+        }
+        return lk; // locked
+    }
 
     // Detection parameters
     int   _maxSideLen    = kDetMaxSideLen;