From 1dcc6b8026a1cce5aae75150af4256c267153fb8 Mon Sep 17 00:00:00 2001
From: Shoyu Vanilla <modulo641@gmail.com>
Date: Tue, 17 Jun 2025 07:21:35 +0900
Subject: [PATCH] fix: Prevent false-positive deadlocks on try_lock

---
 src/rt/mutex.rs  |  3 +++
 src/rt/rwlock.rs |  6 ++++++
 tests/mutex.rs   | 18 ++++++++++++++++++
 tests/rwlock.rs  | 18 ++++++++++++++++++
 4 files changed, 45 insertions(+)

diff --git a/src/rt/mutex.rs b/src/rt/mutex.rs
index f2e12701..427bafb5 100644
--- a/src/rt/mutex.rs
+++ b/src/rt/mutex.rs
@@ -47,6 +47,9 @@ impl Mutex {
     }
 
     pub(crate) fn try_acquire_lock(&self, location: Location) -> bool {
+        if self.is_locked() {
+            return false;
+        }
         self.state.branch_opaque(location);
         self.post_acquire()
     }
diff --git a/src/rt/rwlock.rs b/src/rt/rwlock.rs
index cd8ec9b9..23639e24 100644
--- a/src/rt/rwlock.rs
+++ b/src/rt/rwlock.rs
@@ -79,11 +79,17 @@ impl RwLock {
     }
 
     pub(crate) fn try_acquire_read_lock(&self, location: Location) -> bool {
+        if self.is_write_locked() {
+            return false;
+        }
         self.state.branch_action(Action::Read, location);
         self.post_acquire_read_lock()
     }
 
     pub(crate) fn try_acquire_write_lock(&self, location: Location) -> bool {
+        if self.is_write_locked() || self.is_read_locked() {
+            return false;
+        }
         self.state.branch_action(Action::Write, location);
         self.post_acquire_write_lock()
     }
diff --git a/tests/mutex.rs b/tests/mutex.rs
index fdb3f4bf..905950a7 100644
--- a/tests/mutex.rs
+++ b/tests/mutex.rs
@@ -91,3 +91,21 @@ fn mutex_into_inner() {
         assert_eq!(lock, 2);
     })
 }
+
+#[test]
+fn try_lock_no_block() {
+    loom::model(|| {
+        let lock = Rc::new(Mutex::new(0));
+        let lock2 = lock.clone();
+
+        let th = thread::spawn(move || {
+            let _ = lock.try_lock();
+        });
+
+        let guard = lock2.try_lock();
+
+        th.join().unwrap();
+
+        drop(guard)
+    })
+}
diff --git a/tests/rwlock.rs b/tests/rwlock.rs
index 1ca6728a..37495321 100644
--- a/tests/rwlock.rs
+++ b/tests/rwlock.rs
@@ -162,3 +162,21 @@ fn rwlock_into_inner() {
         assert_eq!(lock, 2);
     })
 }
+
+#[test]
+fn rwlock_try_write_no_block() {
+    loom::model(|| {
+        let lock = Rc::new(RwLock::new(0));
+        let lock2 = lock.clone();
+
+        let th = thread::spawn(move || {
+            let _ = lock.try_read();
+        });
+
+        let guard = lock2.try_write();
+
+        th.join().unwrap();
+
+        drop(guard)
+    })
+}