Auto merge of #27016 - gterzian:fix_closing_window, r=jdm,paulrouget

Ensure clean shutdown of JS threads

<!-- Please describe your changes on the following line: -->

FIX https://github.com/servo/servo/issues/26685
FIX https://github.com/servo/servo/issues/26996
FIX https://github.com/servo/servo/issues/9672
FIX #27027

---
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- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #___ (GitHub issue number if applicable)

<!-- Either: -->
- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because ___

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components/script/dom/bindings/trace.rs

@@ -42,7 +42,7 @@ use crate::dom::gpucommandencoder::GPUCommandEncoderState;
 use crate::dom::htmlimageelement::SourceSet;
 use crate::dom::htmlmediaelement::{HTMLMediaElementFetchContext, MediaFrameRenderer};
 use crate::dom::identityhub::Identities;
-use crate::script_runtime::StreamConsumer;
+use crate::script_runtime::{ContextForRequestInterrupt, StreamConsumer};
 use crate::script_thread::IncompleteParserContexts;
 use crate::task::TaskBox;
 use app_units::Au;
@@ -501,6 +501,7 @@ unsafe_no_jsmanaged_fields!(TimelineMarkerType);
 unsafe_no_jsmanaged_fields!(WorkerId);
 unsafe_no_jsmanaged_fields!(BufferQueue, QuirksMode, StrTendril);
 unsafe_no_jsmanaged_fields!(Runtime);
+unsafe_no_jsmanaged_fields!(ContextForRequestInterrupt);
 unsafe_no_jsmanaged_fields!(HeaderMap, Method);
 unsafe_no_jsmanaged_fields!(WindowProxyHandler);
 unsafe_no_jsmanaged_fields!(UntrustedNodeAddress, OpaqueNode);

components/script/dom/dedicatedworkerglobalscope.rs

@@ -30,7 +30,8 @@ use crate::fetch::load_whole_resource;
 use crate::realms::{enter_realm, AlreadyInRealm, InRealm};
 use crate::script_runtime::ScriptThreadEventCategory::WorkerEvent;
 use crate::script_runtime::{
-    new_child_runtime, CommonScriptMsg, JSContext as SafeJSContext, Runtime, ScriptChan, ScriptPort,
+    new_child_runtime, CommonScriptMsg, ContextForRequestInterrupt, JSContext as SafeJSContext,
+    Runtime, ScriptChan, ScriptPort,
 };
 use crate::task_queue::{QueuedTask, QueuedTaskConversion, TaskQueue};
 use crate::task_source::networking::NetworkingTaskSource;
@@ -256,7 +257,7 @@ impl DedicatedWorkerGlobalScope {
                 worker_url,
                 runtime,
                 from_devtools_receiver,
-                Some(closing),
+                closing,
                 gpu_id_hub,
             ),
             task_queue: TaskQueue::new(receiver, own_sender.clone()),
@@ -324,6 +325,7 @@ impl DedicatedWorkerGlobalScope {
         browsing_context: Option<BrowsingContextId>,
         gpu_id_hub: Arc<Mutex<Identities>>,
         control_receiver: Receiver<DedicatedWorkerControlMsg>,
+        context_sender: Sender<ContextForRequestInterrupt>,
     ) -> JoinHandle<()> {
         let serialized_worker_url = worker_url.to_string();
         let name = format!("WebWorker for {}", serialized_worker_url);
@@ -377,6 +379,8 @@ impl DedicatedWorkerGlobalScope {
                     new_child_runtime(parent, Some(task_source))
                 };
 
+                let _ = context_sender.send(ContextForRequestInterrupt::new(runtime.cx()));
+
                 let (devtools_mpsc_chan, devtools_mpsc_port) = unbounded();
                 ROUTER.route_ipc_receiver_to_crossbeam_sender(
                     from_devtools_receiver,

components/script/dom/globalscope.rs

@@ -52,7 +52,9 @@ use crate::dom::workletglobalscope::WorkletGlobalScope;
 use crate::microtask::{Microtask, MicrotaskQueue, UserMicrotask};
 use crate::realms::{enter_realm, AlreadyInRealm, InRealm};
 use crate::script_module::ModuleTree;
-use crate::script_runtime::{CommonScriptMsg, JSContext as SafeJSContext, ScriptChan, ScriptPort};
+use crate::script_runtime::{
+    CommonScriptMsg, ContextForRequestInterrupt, JSContext as SafeJSContext, ScriptChan, ScriptPort,
+};
 use crate::script_thread::{MainThreadScriptChan, ScriptThread};
 use crate::task::TaskCanceller;
 use crate::task_source::dom_manipulation::DOMManipulationTaskSource;
@@ -130,6 +132,8 @@ pub struct AutoCloseWorker {
     /// A sender of control messages,
     /// currently only used to signal shutdown.
     control_sender: Sender<DedicatedWorkerControlMsg>,
+    /// The context to request an interrupt on the worker thread.
+    context: ContextForRequestInterrupt,
 }
 
 impl Drop for AutoCloseWorker {
@@ -146,6 +150,8 @@ impl Drop for AutoCloseWorker {
             warn!("Couldn't send an exit message to a dedicated worker.");
         }
 
+        self.context.request_interrupt();
+
         // TODO: step 2 and 3.
         // Step 4 is unnecessary since we don't use actual ports for dedicated workers.
         if self
@@ -2049,6 +2055,7 @@ impl GlobalScope {
         closing: Arc<AtomicBool>,
         join_handle: JoinHandle<()>,
         control_sender: Sender<DedicatedWorkerControlMsg>,
+        context: ContextForRequestInterrupt,
     ) {
         self.list_auto_close_worker
             .borrow_mut()
@@ -2056,6 +2063,7 @@ impl GlobalScope {
                 closing,
                 join_handle: Some(join_handle),
                 control_sender: control_sender,
+                context,
             });
     }
 
@@ -2713,6 +2721,20 @@ impl GlobalScope {
         unreachable!();
     }
 
+    /// Returns a boolean indicating whether the event-loop
+    /// where this global is running on can continue running JS.
+    pub fn can_continue_running(&self) -> bool {
+        if self.downcast::<Window>().is_some() {
+            return ScriptThread::can_continue_running();
+        }
+        if let Some(worker) = self.downcast::<WorkerGlobalScope>() {
+            return !worker.is_closing();
+        }
+
+        // TODO: plug worklets into this.
+        true
+    }
+
     /// Returns the task canceller of this global to ensure that everything is
     /// properly cancelled when the global scope is destroyed.
     pub fn task_canceller(&self, name: TaskSourceName) -> TaskCanceller {
@@ -2730,11 +2752,14 @@ impl GlobalScope {
 
     /// Perform a microtask checkpoint.
     pub fn perform_a_microtask_checkpoint(&self) {
-        self.microtask_queue.checkpoint(
-            self.get_cx(),
-            |_| Some(DomRoot::from_ref(self)),
-            vec![DomRoot::from_ref(self)],
-        );
+        // Only perform the checkpoint if we're not shutting down.
+        if self.can_continue_running() {
+            self.microtask_queue.checkpoint(
+                self.get_cx(),
+                |_| Some(DomRoot::from_ref(self)),
+                vec![DomRoot::from_ref(self)],
+            );
+        }
     }
 
     /// Enqueue a microtask for subsequent execution.
@@ -2761,8 +2786,9 @@ impl GlobalScope {
     }
 
     /// Process a single event as if it were the next event
-    /// in the thread queue for this global scope.
-    pub fn process_event(&self, msg: CommonScriptMsg) {
+    /// in the queue for the event-loop where this global scope is running on.
+    /// Returns a boolean indicating whether further events should be processed.
+    pub fn process_event(&self, msg: CommonScriptMsg) -> bool {
         if self.is::<Window>() {
             return ScriptThread::process_event(msg);
         }

components/script/dom/serviceworkerglobalscope.rs

@@ -25,7 +25,8 @@ use crate::dom::workerglobalscope::WorkerGlobalScope;
 use crate::fetch::load_whole_resource;
 use crate::realms::{enter_realm, AlreadyInRealm, InRealm};
 use crate::script_runtime::{
-    new_rt_and_cx, CommonScriptMsg, JSContext as SafeJSContext, Runtime, ScriptChan,
+    new_rt_and_cx, CommonScriptMsg, ContextForRequestInterrupt, JSContext as SafeJSContext,
+    Runtime, ScriptChan,
 };
 use crate::task_queue::{QueuedTask, QueuedTaskConversion, TaskQueue};
 use crate::task_source::TaskSourceName;
@@ -44,6 +45,7 @@ use script_traits::{ScopeThings, ServiceWorkerMsg, WorkerGlobalScopeInit, Worker
 use servo_config::pref;
 use servo_rand::random;
 use servo_url::ServoUrl;
+use std::sync::atomic::AtomicBool;
 use std::sync::Arc;
 use std::thread::{self, JoinHandle};
 use std::time::{Duration, Instant};
@@ -225,6 +227,7 @@ impl ServiceWorkerGlobalScope {
         swmanager_sender: IpcSender<ServiceWorkerMsg>,
         scope_url: ServoUrl,
         control_receiver: Receiver<ServiceWorkerControlMsg>,
+        closing: Arc<AtomicBool>,
     ) -> ServiceWorkerGlobalScope {
         ServiceWorkerGlobalScope {
             workerglobalscope: WorkerGlobalScope::new_inherited(
@@ -234,7 +237,7 @@ impl ServiceWorkerGlobalScope {
                 worker_url,
                 runtime,
                 from_devtools_receiver,
-                None,
+                closing,
                 Arc::new(Mutex::new(Identities::new())),
             ),
             task_queue: TaskQueue::new(receiver, own_sender.clone()),
@@ -258,6 +261,7 @@ impl ServiceWorkerGlobalScope {
         swmanager_sender: IpcSender<ServiceWorkerMsg>,
         scope_url: ServoUrl,
         control_receiver: Receiver<ServiceWorkerControlMsg>,
+        closing: Arc<AtomicBool>,
     ) -> DomRoot<ServiceWorkerGlobalScope> {
         let cx = runtime.cx();
         let scope = Box::new(ServiceWorkerGlobalScope::new_inherited(
@@ -271,6 +275,7 @@ impl ServiceWorkerGlobalScope {
             swmanager_sender,
             scope_url,
             control_receiver,
+            closing,
         ));
         unsafe { ServiceWorkerGlobalScopeBinding::Wrap(SafeJSContext::from_ptr(cx), scope) }
     }
@@ -285,6 +290,8 @@ impl ServiceWorkerGlobalScope {
         swmanager_sender: IpcSender<ServiceWorkerMsg>,
         scope_url: ServoUrl,
         control_receiver: Receiver<ServiceWorkerControlMsg>,
+        context_sender: Sender<ContextForRequestInterrupt>,
+        closing: Arc<AtomicBool>,
     ) -> JoinHandle<()> {
         let ScopeThings {
             script_url,
@@ -300,6 +307,8 @@ impl ServiceWorkerGlobalScope {
             .spawn(move || {
                 thread_state::initialize(ThreadState::SCRIPT | ThreadState::IN_WORKER);
                 let runtime = new_rt_and_cx(None);
+                let _ = context_sender.send(ContextForRequestInterrupt::new(runtime.cx()));
+
                 let roots = RootCollection::new();
                 let _stack_roots = ThreadLocalStackRoots::new(&roots);
 
@@ -330,6 +339,7 @@ impl ServiceWorkerGlobalScope {
                     swmanager_sender,
                     scope_url,
                     control_receiver,
+                    closing,
                 );
 
                 let referrer = referrer_url

components/script/dom/worker.rs

@@ -125,6 +125,7 @@ impl Worker {
         let init = prepare_workerscope_init(global, Some(devtools_sender), Some(worker_id));
 
         let (control_sender, control_receiver) = unbounded();
+        let (context_sender, context_receiver) = unbounded();
 
         let join_handle = DedicatedWorkerGlobalScope::run_worker_scope(
             init,
@@ -142,9 +143,14 @@ impl Worker {
             browsing_context,
             global.wgpu_id_hub(),
             control_receiver,
+            context_sender,
         );
 
-        global.track_worker(closing, join_handle, control_sender);
+        let context = context_receiver
+            .recv()
+            .expect("Couldn't receive a context for worker.");
+
+        global.track_worker(closing, join_handle, control_sender, context);
 
         Ok(worker)
     }

components/script/dom/workerglobalscope.rs

@@ -98,7 +98,7 @@ pub struct WorkerGlobalScope {
     worker_id: WorkerId,
     worker_url: DomRefCell<ServoUrl>,
     #[ignore_malloc_size_of = "Arc"]
-    closing: Option<Arc<AtomicBool>>,
+    closing: Arc<AtomicBool>,
     #[ignore_malloc_size_of = "Defined in js"]
     runtime: DomRefCell<Option<Runtime>>,
     location: MutNullableDom<WorkerLocation>,
@@ -126,7 +126,7 @@ impl WorkerGlobalScope {
         worker_url: ServoUrl,
         runtime: Runtime,
         from_devtools_receiver: Receiver<DevtoolScriptControlMsg>,
-        closing: Option<Arc<AtomicBool>>,
+        closing: Arc<AtomicBool>,
         gpu_id_hub: Arc<Mutex<Identities>>,
     ) -> Self {
         // Install a pipeline-namespace in the current thread.
@@ -193,11 +193,7 @@ impl WorkerGlobalScope {
     }
 
     pub fn is_closing(&self) -> bool {
-        if let Some(ref closing) = self.closing {
-            closing.load(Ordering::SeqCst)
-        } else {
-            false
-        }
+        self.closing.load(Ordering::SeqCst)
     }
 
     pub fn get_url(&self) -> Ref<ServoUrl> {
@@ -494,7 +490,13 @@ impl WorkerGlobalScope {
         }
     }
 
-    pub fn process_event(&self, msg: CommonScriptMsg) {
+    /// Process a single event as if it were the next event
+    /// in the queue for this worker event-loop.
+    /// Returns a boolean indicating whether further events should be processed.
+    pub fn process_event(&self, msg: CommonScriptMsg) -> bool {
+        if self.is_closing() {
+            return false;
+        }
         match msg {
             CommonScriptMsg::Task(_, task, _, _) => task.run_box(),
             CommonScriptMsg::CollectReports(reports_chan) => {
@@ -504,11 +506,10 @@ impl WorkerGlobalScope {
                 reports_chan.send(reports);
             },
         }
+        true
     }
 
     pub fn close(&self) {
-        if let Some(ref closing) = self.closing {
-            closing.store(true, Ordering::SeqCst);
-        }
+        self.closing.store(true, Ordering::SeqCst);
     }
 }

components/script/dom/xmlhttprequest.rs

@@ -1544,7 +1544,10 @@ impl XMLHttpRequest {
 
         if let Some(script_port) = script_port {
             loop {
-                global.process_event(script_port.recv().unwrap());
+                if !global.process_event(script_port.recv().unwrap()) {
+                    // We're exiting.
+                    return Err(Error::Abort);
+                }
                 let context = context.lock().unwrap();
                 let sync_status = context.sync_status.borrow();
                 if let Some(ref status) = *sync_status {

components/script/microtask.rs

@@ -147,4 +147,8 @@ impl MicrotaskQueue {
     pub fn empty(&self) -> bool {
         self.microtask_queue.borrow().is_empty()
     }
+
+    pub fn clear(&self) {
+        self.microtask_queue.borrow_mut().clear();
+    }
 }

components/script/script_runtime.rs

@@ -52,7 +52,10 @@ use js::jsapi::{BuildIdCharVector, DisableIncrementalGC, GCDescription, GCProgre
 use js::jsapi::{Dispatchable as JSRunnable, Dispatchable_MaybeShuttingDown};
 use js::jsapi::{HandleObject, Heap, JobQueue};
 use js::jsapi::{JSContext as RawJSContext, JSTracer, SetDOMCallbacks, SetGCSliceCallback};
-use js::jsapi::{JSGCInvocationKind, JSGCStatus, JS_AddExtraGCRootsTracer, JS_SetGCCallback};
+use js::jsapi::{
+    JSGCInvocationKind, JSGCStatus, JS_AddExtraGCRootsTracer, JS_RequestInterruptCallback,
+    JS_SetGCCallback,
+};
 use js::jsapi::{JSGCMode, JSGCParamKey, JS_SetGCParameter, JS_SetGlobalJitCompilerOption};
 use js::jsapi::{
     JSJitCompilerOption, JS_SetOffthreadIonCompilationEnabled, JS_SetParallelParsingEnabled,
@@ -845,6 +848,34 @@ unsafe fn set_gc_zeal_options(cx: *mut RawJSContext) {
 #[cfg(not(feature = "debugmozjs"))]
 unsafe fn set_gc_zeal_options(_: *mut RawJSContext) {}
 
+#[repr(transparent)]
+/// A wrapper around a JSContext that is Send,
+/// enabling an interrupt to be requested
+/// from a thread other than the one running JS using that context.
+pub struct ContextForRequestInterrupt(*mut RawJSContext);
+
+impl ContextForRequestInterrupt {
+    pub fn new(context: *mut RawJSContext) -> ContextForRequestInterrupt {
+        ContextForRequestInterrupt(context)
+    }
+
+    #[allow(unsafe_code)]
+    /// Can be called from any thread, to request the callback set by
+    /// JS_AddInterruptCallback to be called
+    /// on the thread where that context is running.
+    pub fn request_interrupt(&self) {
+        unsafe {
+            JS_RequestInterruptCallback(self.0);
+        }
+    }
+}
+
+#[allow(unsafe_code)]
+/// It is safe to call `JS_RequestInterruptCallback(cx)` from any thread.
+/// See the docs for the corresponding `requestInterrupt` method,
+/// at `mozjs/js/src/vm/JSContext.h`.
+unsafe impl Send for ContextForRequestInterrupt {}
+
 #[derive(Clone, Copy)]
 #[repr(transparent)]
 pub struct JSContext(*mut RawJSContext);

components/script/script_thread.rs

@@ -63,7 +63,9 @@ use crate::dom::workletglobalscope::WorkletGlobalScopeInit;
 use crate::fetch::FetchCanceller;
 use crate::microtask::{Microtask, MicrotaskQueue};
 use crate::realms::enter_realm;
-use crate::script_runtime::{get_reports, new_rt_and_cx, JSContext, Runtime, ScriptPort};
+use crate::script_runtime::{
+    get_reports, new_rt_and_cx, ContextForRequestInterrupt, JSContext, Runtime, ScriptPort,
+};
 use crate::script_runtime::{CommonScriptMsg, ScriptChan, ScriptThreadEventCategory};
 use crate::task_manager::TaskManager;
 use crate::task_queue::{QueuedTask, QueuedTaskConversion, TaskQueue};
@@ -97,14 +99,17 @@ use ipc_channel::ipc::{self, IpcSender};
 use ipc_channel::router::ROUTER;
 use js::glue::GetWindowProxyClass;
 use js::jsapi::JS_SetWrapObjectCallbacks;
-use js::jsapi::{JSTracer, SetWindowProxyClass};
+use js::jsapi::{
+    JSContext as UnsafeJSContext, JSTracer, JS_AddInterruptCallback, SetWindowProxyClass,
+};
 use js::jsval::UndefinedValue;
 use js::rust::ParentRuntime;
 use media::WindowGLContext;
 use metrics::{PaintTimeMetrics, MAX_TASK_NS};
 use mime::{self, Mime};
 use msg::constellation_msg::{
-    BackgroundHangMonitor, BackgroundHangMonitorRegister, ScriptHangAnnotation,
+    BackgroundHangMonitor, BackgroundHangMonitorExitSignal, BackgroundHangMonitorRegister,
+    ScriptHangAnnotation,
 };
 use msg::constellation_msg::{BrowsingContextId, HistoryStateId, PipelineId};
 use msg::constellation_msg::{HangAnnotation, MonitoredComponentId, MonitoredComponentType};
@@ -149,7 +154,7 @@ use std::option::Option;
 use std::ptr;
 use std::rc::Rc;
 use std::result::Result;
-use std::sync::atomic::AtomicBool;
+use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Arc;
 use std::thread;
 use std::time::{Duration, SystemTime};
@@ -531,9 +536,11 @@ pub struct ScriptThread {
     task_queue: TaskQueue<MainThreadScriptMsg>,
 
     /// A handle to register associated layout threads for hang-monitoring.
-    background_hang_monitor_register: Option<Box<dyn BackgroundHangMonitorRegister>>,
+    background_hang_monitor_register: Box<dyn BackgroundHangMonitorRegister>,
     /// The dedicated means of communication with the background-hang-monitor for this script-thread.
-    background_hang_monitor: Option<Box<dyn BackgroundHangMonitor>>,
+    background_hang_monitor: Box<dyn BackgroundHangMonitor>,
+    /// A flag set to `true` by the BHM on exit, and checked from within the interrupt handler.
+    closing: Arc<AtomicBool>,
 
     /// A channel to hand out to script thread-based entities that need to be able to enqueue
     /// events in the event queue.
@@ -686,6 +693,27 @@ pub struct ScriptThread {
     webgpu_port: RefCell<Option<Receiver<WebGPUMsg>>>,
 }
 
+struct BHMExitSignal {
+    closing: Arc<AtomicBool>,
+    js_context: ContextForRequestInterrupt,
+}
+
+impl BackgroundHangMonitorExitSignal for BHMExitSignal {
+    fn signal_to_exit(&self) {
+        self.closing.store(true, Ordering::SeqCst);
+        self.js_context.request_interrupt();
+    }
+}
+
+#[allow(unsafe_code)]
+unsafe extern "C" fn interrupt_callback(_cx: *mut UnsafeJSContext) -> bool {
+    let res = ScriptThread::can_continue_running();
+    if !res {
+        ScriptThread::prepare_for_shutdown();
+    }
+    res
+}
+
 /// In the event of thread panic, all data on the stack runs its destructor. However, there
 /// are no reachable, owning pointers to the DOM memory, so it never gets freed by default
 /// when the script thread fails. The ScriptMemoryFailsafe uses the destructor bomb pattern
@@ -818,6 +846,20 @@ impl ScriptThread {
         })
     }
 
+    pub fn can_continue_running() -> bool {
+        SCRIPT_THREAD_ROOT.with(|root| {
+            let script_thread = unsafe { &*root.get().unwrap() };
+            script_thread.can_continue_running_inner()
+        })
+    }
+
+    pub fn prepare_for_shutdown() {
+        SCRIPT_THREAD_ROOT.with(|root| {
+            let script_thread = unsafe { &*root.get().unwrap() };
+            script_thread.prepare_for_shutdown_inner();
+        })
+    }
+
     pub fn set_mutation_observer_microtask_queued(value: bool) {
         SCRIPT_THREAD_ROOT.with(|root| {
             let script_thread = unsafe { &*root.get().unwrap() };
@@ -876,13 +918,22 @@ impl ScriptThread {
         })
     }
 
-    pub fn process_event(msg: CommonScriptMsg) {
+    /// Process a single event as if it were the next event
+    /// in the queue for this window event-loop.
+    /// Returns a boolean indicating whether further events should be processed.
+    pub fn process_event(msg: CommonScriptMsg) -> bool {
         SCRIPT_THREAD_ROOT.with(|root| {
             if let Some(script_thread) = root.get() {
                 let script_thread = unsafe { &*script_thread };
-                script_thread.handle_msg_from_script(MainThreadScriptMsg::Common(msg));
+                if !script_thread.can_continue_running_inner() {
+                    return false;
+                } else {
+                    script_thread.handle_msg_from_script(MainThreadScriptMsg::Common(msg));
+                    return true;
+                }
             }
-        });
+            false
+        })
     }
 
     // https://html.spec.whatwg.org/multipage/#await-a-stable-state
@@ -1231,6 +1282,7 @@ impl ScriptThread {
         unsafe {
             JS_SetWrapObjectCallbacks(cx, &WRAP_CALLBACKS);
             SetWindowProxyClass(cx, GetWindowProxyClass());
+            JS_AddInterruptCallback(cx, Some(interrupt_callback));
         }
 
         // Ask the router to proxy IPC messages from the devtools to us.
@@ -1242,13 +1294,18 @@ impl ScriptThread {
 
         let task_queue = TaskQueue::new(port, chan.clone());
 
-        let background_hang_monitor = state.background_hang_monitor_register.clone().map(|bhm| {
-            bhm.register_component(
-                MonitoredComponentId(state.id.clone(), MonitoredComponentType::Script),
-                Duration::from_millis(1000),
-                Duration::from_millis(5000),
-            )
-        });
+        let closing = Arc::new(AtomicBool::new(false));
+        let background_hang_monitor_exit_signal = BHMExitSignal {
+            closing: closing.clone(),
+            js_context: ContextForRequestInterrupt::new(cx),
+        };
+
+        let background_hang_monitor = state.background_hang_monitor_register.register_component(
+            MonitoredComponentId(state.id.clone(), MonitoredComponentType::Script),
+            Duration::from_millis(1000),
+            Duration::from_millis(5000),
+            Some(Box::new(background_hang_monitor_exit_signal)),
+        );
 
         // Ask the router to proxy IPC messages from the control port to us.
         let control_port = ROUTER.route_ipc_receiver_to_new_crossbeam_receiver(state.control_port);
@@ -1270,6 +1327,7 @@ impl ScriptThread {
 
             background_hang_monitor_register: state.background_hang_monitor_register,
             background_hang_monitor,
+            closing,
 
             chan: MainThreadScriptChan(chan.clone()),
             dom_manipulation_task_sender: boxed_script_sender.clone(),
@@ -1349,6 +1407,23 @@ impl ScriptThread {
         unsafe { JSContext::from_ptr(self.js_runtime.cx()) }
     }
 
+    /// Check if we are closing.
+    fn can_continue_running_inner(&self) -> bool {
+        if self.closing.load(Ordering::SeqCst) {
+            return false;
+        }
+        true
+    }
+
+    /// We are closing, ensure no script can run and potentially hang.
+    fn prepare_for_shutdown_inner(&self) {
+        let docs = self.documents.borrow();
+        for (_, document) in docs.iter() {
+            let window = document.window();
+            window.ignore_all_tasks();
+        }
+    }
+
     /// Starts the script thread. After calling this method, the script thread will loop receiving
     /// messages on its port.
     pub fn start(&self) {
@@ -1386,9 +1461,7 @@ impl ScriptThread {
         let mut sequential = vec![];
 
         // Notify the background-hang-monitor we are waiting for an event.
-        self.background_hang_monitor
-            .as_ref()
-            .map(|bhm| bhm.notify_wait());
+        self.background_hang_monitor.notify_wait();
 
         // Receive at least one message so we don't spinloop.
         debug!("Waiting for event.");
@@ -1530,6 +1603,24 @@ impl ScriptThread {
             let category = self.categorize_msg(&msg);
             let pipeline_id = self.message_to_pipeline(&msg);
 
+            if self.closing.load(Ordering::SeqCst) {
+                // If we've received the closed signal from the BHM, only handle exit messages.
+                match msg {
+                    FromConstellation(ConstellationControlMsg::ExitScriptThread) => {
+                        self.handle_exit_script_thread_msg();
+                        return false;
+                    },
+                    FromConstellation(ConstellationControlMsg::ExitPipeline(
+                        pipeline_id,
+                        discard_browsing_context,
+                    )) => {
+                        self.handle_exit_pipeline_msg(pipeline_id, discard_browsing_context);
+                    },
+                    _ => {},
+                }
+                continue;
+            }
+
             let result = self.profile_event(category, pipeline_id, move || {
                 match msg {
                     FromConstellation(ConstellationControlMsg::ExitScriptThread) => {
@@ -1546,12 +1637,12 @@ impl ScriptThread {
                 None
             });
 
-            // https://html.spec.whatwg.org/multipage/#event-loop-processing-model step 6
-            self.perform_a_microtask_checkpoint();
-
             if let Some(retval) = result {
                 return retval;
             }
+
+            // https://html.spec.whatwg.org/multipage/#event-loop-processing-model step 6
+            self.perform_a_microtask_checkpoint();
         }
 
         {
@@ -1665,8 +1756,7 @@ impl ScriptThread {
             ScriptThreadEventCategory::WebGPUMsg => ScriptHangAnnotation::WebGPUMsg,
         };
         self.background_hang_monitor
-            .as_ref()
-            .map(|bhm| bhm.notify_activity(HangAnnotation::Script(hang_annotation)));
+            .notify_activity(HangAnnotation::Script(hang_annotation));
     }
 
     fn message_to_pipeline(&self, msg: &MixedMessage) -> Option<PipelineId> {
@@ -2855,9 +2945,7 @@ impl ScriptThread {
             self.handle_exit_pipeline_msg(pipeline_id, DiscardBrowsingContext::Yes);
         }
 
-        self.background_hang_monitor
-            .as_ref()
-            .map(|bhm| bhm.unregister());
+        self.background_hang_monitor.unregister();
 
         // If we're in multiprocess mode, shut-down the IPC router for this process.
         if opts::multiprocess() {
@@ -3867,18 +3955,21 @@ impl ScriptThread {
     }
 
     fn perform_a_microtask_checkpoint(&self) {
-        let globals = self
-            .documents
-            .borrow()
-            .iter()
-            .map(|(_id, document)| document.global())
-            .collect();
+        // Only perform the checkpoint if we're not shutting down.
+        if self.can_continue_running_inner() {
+            let globals = self
+                .documents
+                .borrow()
+                .iter()
+                .map(|(_id, document)| document.global())
+                .collect();
 
-        self.microtask_queue.checkpoint(
-            self.get_cx(),
-            |id| self.documents.borrow().find_global(id),
-            globals,
-        )
+            self.microtask_queue.checkpoint(
+                self.get_cx(),
+                |id| self.documents.borrow().find_global(id),
+                globals,
+            )
+        }
     }
 }
 

components/script/serviceworker_manager.rs

@@ -12,6 +12,7 @@ use crate::dom::serviceworkerglobalscope::{
     ServiceWorkerControlMsg, ServiceWorkerGlobalScope, ServiceWorkerScriptMsg,
 };
 use crate::dom::serviceworkerregistration::longest_prefix_match;
+use crate::script_runtime::ContextForRequestInterrupt;
 use crossbeam_channel::{unbounded, Receiver, RecvError, Sender};
 use ipc_channel::ipc::{self, IpcSender};
 use ipc_channel::router::ROUTER;
@@ -26,6 +27,8 @@ use servo_config::pref;
 use servo_url::ImmutableOrigin;
 use servo_url::ServoUrl;
 use std::collections::HashMap;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Arc;
 use std::thread::{self, JoinHandle};
 
 enum Message {
@@ -93,6 +96,15 @@ impl Drop for ServiceWorkerRegistration {
             warn!("Failed to send exit message to service worker scope.");
         }
 
+        self.closing
+            .take()
+            .expect("No close flag for worker")
+            .store(true, Ordering::SeqCst);
+        self.context
+            .take()
+            .expect("No context to request interrupt.")
+            .request_interrupt();
+
         // TODO: Step 1, 2 and 3.
         if self
             .join_handle
@@ -121,6 +133,10 @@ struct ServiceWorkerRegistration {
     control_sender: Option<Sender<ServiceWorkerControlMsg>>,
     /// A handle to join on the worker thread.
     join_handle: Option<JoinHandle<()>>,
+    /// A context to request an interrupt.
+    context: Option<ContextForRequestInterrupt>,
+    /// The closing flag for the worker.
+    closing: Option<Arc<AtomicBool>>,
 }
 
 impl ServiceWorkerRegistration {
@@ -132,6 +148,8 @@ impl ServiceWorkerRegistration {
             installing_worker: None,
             join_handle: None,
             control_sender: None,
+            context: None,
+            closing: None,
         }
     }
 
@@ -139,12 +157,20 @@ impl ServiceWorkerRegistration {
         &mut self,
         join_handle: JoinHandle<()>,
         control_sender: Sender<ServiceWorkerControlMsg>,
+        context: ContextForRequestInterrupt,
+        closing: Arc<AtomicBool>,
     ) {
         assert!(self.join_handle.is_none());
         self.join_handle = Some(join_handle);
 
         assert!(self.control_sender.is_none());
         self.control_sender = Some(control_sender);
+
+        assert!(self.context.is_none());
+        self.context = Some(context);
+
+        assert!(self.closing.is_none());
+        self.closing = Some(closing);
     }
 
     /// <https://w3c.github.io/ServiceWorker/#get-newest-worker>
@@ -378,11 +404,11 @@ impl ServiceWorkerManager {
 
             // Very roughly steps 5 to 18.
             // TODO: implement all steps precisely.
-            let (new_worker, join_handle, control_sender) =
+            let (new_worker, join_handle, control_sender, context, closing) =
                 update_serviceworker(self.own_sender.clone(), job.scope_url.clone(), scope_things);
 
             // Since we've just started the worker thread, ensure we can shut it down later.
-            registration.note_worker_thread(join_handle, control_sender);
+            registration.note_worker_thread(join_handle, control_sender, context, closing);
 
             // Step 19, run Install.
 
@@ -422,12 +448,16 @@ fn update_serviceworker(
     ServiceWorker,
     JoinHandle<()>,
     Sender<ServiceWorkerControlMsg>,
+    ContextForRequestInterrupt,
+    Arc<AtomicBool>,
 ) {
     let (sender, receiver) = unbounded();
     let (_devtools_sender, devtools_receiver) = ipc::channel().unwrap();
     let worker_id = ServiceWorkerId::new();
 
     let (control_sender, control_receiver) = unbounded();
+    let (context_sender, context_receiver) = unbounded();
+    let closing = Arc::new(AtomicBool::new(false));
 
     let join_handle = ServiceWorkerGlobalScope::run_serviceworker_scope(
         scope_things.clone(),
@@ -437,12 +467,20 @@ fn update_serviceworker(
         own_sender,
         scope_url.clone(),
         control_receiver,
+        context_sender,
+        closing.clone(),
     );
 
+    let context = context_receiver
+        .recv()
+        .expect("Couldn't receive a context for worker.");
+
     (
         ServiceWorker::new(scope_things.script_url, sender, worker_id),
         join_handle,
         control_sender,
+        context,
+        closing,
     )
 }
 

components/script/task.rs

@@ -69,7 +69,7 @@ impl fmt::Debug for dyn TaskBox {
 /// Encapsulated state required to create cancellable tasks from non-script threads.
 #[derive(Clone)]
 pub struct TaskCanceller {
-    pub cancelled: Option<Arc<AtomicBool>>,
+    pub cancelled: Arc<AtomicBool>,
 }
 
 impl TaskCanceller {
@@ -88,7 +88,7 @@ impl TaskCanceller {
 
 /// A task that can be cancelled by toggling a shared flag.
 pub struct CancellableTask<T: TaskOnce> {
-    cancelled: Option<Arc<AtomicBool>>,
+    cancelled: Arc<AtomicBool>,
     inner: T,
 }
 
@@ -97,9 +97,7 @@ where
     T: TaskOnce,
 {
     fn is_cancelled(&self) -> bool {
-        self.cancelled
-            .as_ref()
-            .map_or(false, |cancelled| cancelled.load(Ordering::SeqCst))
+        self.cancelled.load(Ordering::SeqCst)
     }
 }
 

components/script/task_manager.rs

@@ -182,7 +182,7 @@ impl TaskManager {
         let mut flags = self.task_cancellers.borrow_mut();
         let cancel_flag = flags.entry(name).or_insert(Default::default());
         TaskCanceller {
-            cancelled: Some(cancel_flag.clone()),
+            cancelled: cancel_flag.clone(),
         }
     }
 }

components/script/timers.rs

@@ -218,6 +218,13 @@ impl OneshotTimers {
         }
 
         for timer in timers_to_run {
+            // Since timers can be coalesced together inside a task,
+            // this loop can keep running, including after an interrupt of the JS,
+            // and prevent a clean-shutdown of a JS-running thread.
+            // This check prevents such a situation.
+            if !global.can_continue_running() {
+                return;
+            }
             let callback = timer.callback;
             callback.invoke(global, &self.js_timers);
         }