runtime: panic when event_interval is set to 0 (#7838)

Author: mattiapitossi

tokio/src/runtime/builder.rs

@@ -1123,6 +1123,10 @@ impl Builder {
     /// will minimize that overhead while still keeping the scheduler responsive to
     /// events.
     ///
+    /// # Panics
+    ///
+    /// This function will panic if 0 is passed as an argument.
+    ///
     /// # Examples
     ///
     /// ```
@@ -1136,7 +1140,9 @@ impl Builder {
     /// # }
     /// # }
     /// ```
+    #[track_caller]
     pub fn event_interval(&mut self, val: u32) -> &mut Self {
+        assert!(val > 0, "event_interval must be greater than 0");
         self.event_interval = val;
         self
     }

tokio/tests/rt_panic.rs

@@ -82,6 +82,18 @@ fn builder_global_queue_interval_panic_caller() -> Result<(), Box<dyn Error>> {
     Ok(())
 }
 
+#[test]
+fn builder_event_interval_interval_panic_caller() -> Result<(), Box<dyn Error>> {
+    let panic_location_file = test_panic(|| {
+        let _ = Builder::new_multi_thread().event_interval(0).build();
+    });
+
+    // The panic location should be in this file
+    assert_eq!(&panic_location_file.unwrap(), file!());
+
+    Ok(())
+}
+
 fn current_thread() -> Runtime {
     tokio::runtime::Builder::new_current_thread()
         .enable_all()