clear_after_fork (#6933)

crates/vm/src/object/core.rs

@@ -197,6 +197,15 @@ mod weakref_lock {
             core::hint::spin_loop();
         }
     }
+
+    /// Reset all weakref stripe locks after fork in child process.
+    /// Locks held by parent threads would cause infinite spin in the child.
+    #[cfg(unix)]
+    pub(crate) fn reset_all_after_fork() {
+        for lock in &LOCKS {
+            lock.store(0, Ordering::Release);
+        }
+    }
 }
 
 #[cfg(not(feature = "threading"))]
@@ -212,6 +221,13 @@ mod weakref_lock {
     }
 }
 
+/// Reset weakref stripe locks after fork. Must be called before any
+/// Python code runs in the child process.
+#[cfg(all(unix, feature = "threading"))]
+pub(crate) fn reset_weakref_locks_after_fork() {
+    weakref_lock::reset_all_after_fork();
+}
+
 // === WeakRefList: inline on every object (tp_weaklist) ===
 
 pub(super) struct WeakRefList {

crates/vm/src/signal.rs

@@ -50,6 +50,16 @@ pub(crate) fn set_triggered() {
     ANY_TRIGGERED.store(true, Ordering::Release);
 }
 
+/// Reset all signal trigger state after fork in child process.
+/// Stale triggers from the parent must not fire in the child.
+#[cfg(unix)]
+pub(crate) fn clear_after_fork() {
+    ANY_TRIGGERED.store(false, Ordering::Release);
+    for trigger in &TRIGGERS {
+        trigger.store(false, Ordering::Relaxed);
+    }
+}
+
 pub fn assert_in_range(signum: i32, vm: &VirtualMachine) -> PyResult<()> {
     if (1..NSIG as i32).contains(&signum) {
         Ok(())

crates/vm/src/stdlib/posix.rs

@@ -660,8 +660,16 @@ pub mod module {
     }
 
     fn py_os_after_fork_child(vm: &VirtualMachine) {
+        // Reset low-level state before any Python code runs in the child.
+        // Signal triggers from the parent must not fire in the child.
+        crate::signal::clear_after_fork();
+        crate::stdlib::signal::_signal::clear_wakeup_fd_after_fork();
+
+        // Reset weakref stripe locks that may have been held during fork.
+        #[cfg(feature = "threading")]
+        crate::object::reset_weakref_locks_after_fork();
+
         // Mark all other threads as done before running Python callbacks
-        // See _PyThread_AfterFork behavior
         #[cfg(feature = "threading")]
         crate::stdlib::thread::after_fork_child(vm);
 

crates/vm/src/stdlib/signal.rs

@@ -679,6 +679,13 @@ pub(crate) mod _signal {
         }
     }
 
+    /// Reset wakeup fd after fork in child process.
+    /// The child must not write to the parent's wakeup fd.
+    #[cfg(unix)]
+    pub(crate) fn clear_wakeup_fd_after_fork() {
+        WAKEUP.store(INVALID_WAKEUP, Ordering::Relaxed);
+    }
+
     pub(crate) fn module_exec(
         vm: &VirtualMachine,
         module: &Py<crate::builtins::PyModule>,