fix(event,graph): run event callbacks outside the locks they live under

crates/hiroz-tests/tests/reentrant_event_status.rs

@@ -0,0 +1,161 @@
+//! Re-entrancy audit for endpoint event-status updates.
+//!
+//! `EventsManager` is shared as `Arc<Mutex<..>>`, so `&mut self` proves the
+//! caller holds that mutex — and `update_event_status` fired the callback from
+//! there. The callback is user code the rmw layer hands to an rclcpp executor,
+//! and the first thing it usually does is ask the handle that fired for its
+//! status (`rmw_take_event` → `RmEventHandle::take_event`), locking the same
+//! mutex on the same thread. Non-reentrant, no race needed.
+//!
+//! Fix: record under the lock, drop the guard, invoke.
+//! `record_event_status_with_policy` returns the callback rather than calling
+//! it, and `update_shared_event_status[_with_policy]` is what holders use.
+//!
+//! Each scenario runs on its own thread behind a deadline, so a deadlock fails
+//! the test instead of wedging the suite.
+//!
+//! # What these detect, and what they do not
+//!
+//! Both call `update_shared_event_status`, which this change *introduces* — so
+//! a wholesale revert does not turn them red, it stops this file compiling.
+//! They are not evidence the old shape deadlocked; `reentrant_graph_event.rs`
+//! carries that.
+//!
+//! They are still detectors, for the property rather than the history:
+//! reinstate the callout inside `update_shared_event_status_with_policy` and
+//! both fail on their deadline. That is the regression worth guarding, since
+//! the old entry point is gone.
+
+use std::{
+    sync::{
+        Arc, Mutex,
+        atomic::{AtomicI32, Ordering},
+        mpsc,
+    },
+    thread,
+    time::Duration,
+};
+
+use hiroz::{
+    GidArray,
+    event::{
+        EventsManager, RmEventHandle, ZenohEventType, update_shared_event_status,
+        update_shared_event_status_with_policy,
+    },
+};
+
+/// Budget for one scenario. Generous relative to the work done — anything
+/// slower than this is a hang, not slowness.
+const SCENARIO_TIMEOUT: Duration = Duration::from_secs(30);
+
+/// Run `scenario` on its own thread; fail (rather than hang) past the deadline.
+///
+/// On timeout the worker is deliberately left running: it is blocked on a lock
+/// that will never be released, and there is no sound way to unwind it.
+fn with_deadline(name: &'static str, scenario: impl FnOnce() + Send + 'static) {
+    let (tx, rx) = mpsc::channel();
+    thread::spawn(move || {
+        scenario();
+        let _ = tx.send(());
+    });
+    match rx.recv_timeout(SCENARIO_TIMEOUT) {
+        Ok(()) => {}
+        // The worker panicked and dropped the sender. That is an assertion
+        // failure inside the scenario, NOT a deadlock — reporting it as one
+        // would turn every ordinary test failure into a false deadlock report.
+        Err(mpsc::RecvTimeoutError::Disconnected) => {
+            panic!("{name}: scenario panicked — see the worker thread's panic above")
+        }
+        Err(mpsc::RecvTimeoutError::Timeout) => {
+            panic!("{name}: scenario did not finish within {SCENARIO_TIMEOUT:?} — deadlock")
+        }
+    }
+}
+
+fn gid(n: u8) -> GidArray {
+    let mut g = [0u8; 16];
+    g[0] = n;
+    g
+}
+
+/// The canonical rmw shape: the matched-event callback immediately takes the
+/// status that triggered it.
+///
+/// `take_event` locks the same `Arc<Mutex<EventsManager>>` the update path
+/// holds, so with the callback invoked under that guard this never returns.
+#[test]
+fn event_callback_taking_its_own_status_does_not_deadlock() {
+    with_deadline("event_callback_take_event", || {
+        let mgr = Arc::new(Mutex::new(EventsManager::new(gid(1))));
+        let handle = Arc::new(RmEventHandle::new(
+            mgr.clone(),
+            ZenohEventType::SubscriptionMatched,
+        ));
+
+        let observed = Arc::new(AtomicI32::new(-1));
+        {
+            let handle_in_cb = handle.clone();
+            let observed = observed.clone();
+            handle.set_callback(move |_change| {
+                let status = handle_in_cb.take_event();
+                observed.store(status.total_count, Ordering::SeqCst);
+            });
+        }
+
+        update_shared_event_status(&mgr, ZenohEventType::SubscriptionMatched, 1);
+
+        assert_eq!(
+            observed.load(Ordering::SeqCst),
+            1,
+            "the callback did not observe the status change that triggered it"
+        );
+        // The callback consumed the change counters via `take_event`.
+        assert!(
+            !handle.is_ready(),
+            "take_event inside the callback should have cleared the changed flag"
+        );
+    });
+}
+
+/// A QoS-incompatibility callback that re-arms itself.
+///
+/// `set_callback` locks the manager to install, so a callback that replaces
+/// itself re-enters the outer mutex exactly like `take_event` does. This also
+/// covers the `_with_policy` entry point, which carries the encoded policy kind.
+#[test]
+fn event_callback_reinstalling_itself_does_not_deadlock() {
+    with_deadline("event_callback_reinstall", || {
+        let mgr = Arc::new(Mutex::new(EventsManager::new(gid(2))));
+        let handle = Arc::new(RmEventHandle::new(
+            mgr.clone(),
+            ZenohEventType::RequestedQosIncompatible,
+        ));
+
+        let fired = Arc::new(AtomicI32::new(0));
+        {
+            let handle_in_cb = handle.clone();
+            let fired = fired.clone();
+            handle.set_callback(move |_change| {
+                fired.fetch_add(1, Ordering::SeqCst);
+                // Re-arm with a no-op. Installing takes the manager lock.
+                handle_in_cb.set_callback(|_| {});
+            });
+        }
+
+        update_shared_event_status_with_policy(
+            &mgr,
+            ZenohEventType::RequestedQosIncompatible,
+            1,
+            42,
+        );
+
+        assert_eq!(
+            fired.load(Ordering::SeqCst),
+            1,
+            "the re-arming callback did not run"
+        );
+        let status = handle.take_event();
+        assert_eq!(status.total_count, 1);
+        assert_eq!(status.last_policy_kind, 42);
+    });
+}