diff --git a/src/Processors/IProcessor.h b/src/Processors/IProcessor.h
index c9dd7d8d77d..34322acb2af 100644
--- a/src/Processors/IProcessor.h
+++ b/src/Processors/IProcessor.h
@@ -237,11 +237,12 @@ public:
 
     /// In case if query was cancelled executor will wait till all processors finish their jobs.
     /// Generally, there is no reason to check this flag. However, it may be reasonable for long operations (e.g. i/o).
-    bool isCancelled() const { return is_cancelled; }
+    bool isCancelled() const { return is_cancelled.load(std::memory_order_acquire); }
     void cancel()
     {
-        is_cancelled = true;
-        onCancel();
+        bool already_cancelled = is_cancelled.exchange(true, std::memory_order_acq_rel);
+        if (!already_cancelled)
+            onCancel();
     }
 
     /// Additional method which is called in case if ports were updated while work() method.