From fb2d2bc2865beeb49a49337fcfe12654cd013ffc Mon Sep 17 00:00:00 2001
From: Oussama Teffahi <70609372+oteffahi@users.noreply.github.com>
Date: Tue, 10 Dec 2024 17:09:22 +0100
Subject: [PATCH] Fix deadlock in subscriber undeclaration (#1649)

* Fix deadlock

* Only update matching listener status for last remote subscriber

* Remove unnecessary drop after changes

* Add unit test for undeclare deadlock
---
 zenoh/src/api/session.rs | 30 ++++++++++++++++++++----------
 zenoh/tests/session.rs   | 12 ++++++++++++
 2 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/zenoh/src/api/session.rs b/zenoh/src/api/session.rs
index 15b7fb4d7b..013536e540 100644
--- a/zenoh/src/api/session.rs
+++ b/zenoh/src/api/session.rs
@@ -1574,19 +1574,29 @@ impl SessionInner {
                                     },
                                 }),
                             });
+                            #[cfg(feature = "unstable")]
+                            {
+                                let state = zread!(self.state);
+                                self.update_matching_status(
+                                    &state,
+                                    &sub_state.key_expr,
+                                    MatchingStatusType::Subscribers,
+                                    false,
+                                )
+                            }
                         }
                     } else {
                         drop(state);
-                    }
-                    #[cfg(feature = "unstable")]
-                    {
-                        let state = zread!(self.state);
-                        self.update_matching_status(
-                            &state,
-                            &sub_state.key_expr,
-                            MatchingStatusType::Subscribers,
-                            false,
-                        )
+                        #[cfg(feature = "unstable")]
+                        {
+                            let state = zread!(self.state);
+                            self.update_matching_status(
+                                &state,
+                                &sub_state.key_expr,
+                                MatchingStatusType::Subscribers,
+                                false,
+                            )
+                        }
                     }
                 }
                 SubscriberKind::LivelinessSubscriber => {
diff --git a/zenoh/tests/session.rs b/zenoh/tests/session.rs
index 3e84249b82..5a18378446 100644
--- a/zenoh/tests/session.rs
+++ b/zenoh/tests/session.rs
@@ -430,3 +430,15 @@ async fn zenoh_session_close_in_background() {
     };
     ztimeout!(close_all);
 }
+
+#[cfg(feature = "unstable")]
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn test_undeclare_subscribers_same_keyexpr() {
+    let key_expr = "test/undeclare/subscribers";
+    let session = zenoh::open(zenoh::Config::default()).await.unwrap();
+    let sub1 = session.declare_subscriber(key_expr).await.unwrap();
+    let sub2 = session.declare_subscriber(key_expr).await.unwrap();
+    tokio::time::sleep(SLEEP).await;
+    ztimeout!(sub1.undeclare()).unwrap();
+    ztimeout!(sub2.undeclare()).unwrap();
+}