fixed python GIL reacquire in case of exception

modules/python/src2/cv2.cpp

@@ -37,9 +37,22 @@ static int failmsg(const char *fmt, ...)
     return 0;
 }
 
+class PyAllowThreads
+{
+public:
+    PyAllowThreads() : _state(PyEval_SaveThread()) {}
+    ~PyAllowThreads() 
+    {
+        PyEval_RestoreThread(_state);
+    }
+private:
+    PyThreadState* _state;
+};
+
 #define ERRWRAP2(expr) \
 try \
 { \
+    PyAllowThreads allowThreads; \
     expr; \
 } \
 catch (const cv::Exception &e) \
@@ -105,22 +118,6 @@ static inline int* refcountFromPyObject(const PyObject* obj)
     return (int*)((size_t)obj + REFCOUNT_OFFSET);
 }
 
-class PyAllowThreads
-{
-public:
-    PyAllowThreads() : _state(PyEval_SaveThread()) 
-    {
-        //printf("+GIL\n");
-    }
-    ~PyAllowThreads()
-    {
-        PyEval_RestoreThread(_state);
-        //printf("-GIL\n");
-    }
-private:
-    PyThreadState* _state;
-};
-
 class NumpyAllocator : public MatAllocator
 {
 public:

modules/python/src2/gen2.py

@@ -19,10 +19,7 @@ gen_template_parse_args = Template("""const char* keywords[] = { $kw_list, NULL
 gen_template_func_body = Template("""$code_decl
     $code_parse
     {
-        {
-            PyAllowThreads allow;
-            $code_fcall;
-        }
+        $code_fcall;
         $code_ret;
     }
 """)