Use try_lock in py_os_after_fork_child

youknowone · youknowone · commit 35748aaefdd3 · 2026-02-17T11:58:15.000+09:00
after_forkers_child.lock() can deadlock in the forked child
if another thread held the mutex at the time of fork.
Use try_lock and skip at-fork callbacks when the lock is
unavailable, matching the pattern used in after_fork_child
for thread_handles.
diff --git a/crates/vm/src/stdlib/posix.rs b/crates/vm/src/stdlib/posix.rs
@@ -716,7 +716,15 @@ pub mod module {
         vm.signal_handlers
             .get_or_init(crate::signal::new_signal_handlers);
 
-        let after_forkers_child: Vec<PyObjectRef> = vm.state.after_forkers_child.lock().clone();
+        let after_forkers_child = match vm.state.after_forkers_child.try_lock() {
+            Some(guard) => guard.clone(),
+            None => {
+                // SAFETY: After fork in child process, only the current thread
+                // exists. The lock holder no longer exists.
+                unsafe { vm.state.after_forkers_child.force_unlock() };
+                vm.state.after_forkers_child.lock().clone()
+            }
+        };
         run_at_forkers(after_forkers_child, false, vm);
     }
 
