Merge pull request #10582 from mshabunin:fix-ocl-concurrent-cache-name

modules/core/src/ocl.cpp

@@ -2070,6 +2070,9 @@ struct Context::Impl
 
     std::string& getPrefixString()
     {
+        if (prefix.empty())
+        {
+            cv::AutoLock lock(program_cache_mutex);
             if (prefix.empty())
             {
                 CV_Assert(!devices.empty());
@@ -2088,11 +2091,15 @@ struct Context::Impl
                     }
                 }
             }
+        }
         return prefix;
     }
 
     std::string& getPrefixBase()
     {
+        if (prefix_base.empty())
+        {
+            cv::AutoLock lock(program_cache_mutex);
             if (prefix_base.empty())
             {
                 const Device& d = devices[0];
@@ -2110,6 +2117,7 @@ struct Context::Impl
                     }
                 }
             }
+        }
         return prefix_base;
     }