Auto merge of #26628 - gterzian:shutdown_workers, r=asajeffrey

Improve worker shutdown

<!-- Please describe your changes on the following line: -->
FIX #26548
FIX #25212

and also  a step towards #26502

---
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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)

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because ___

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components/script/dom/abstractworkerglobalscope.rs

@@ -82,12 +82,15 @@ impl ScriptPort for Receiver<DedicatedWorkerScriptMsg> {
 
 pub trait WorkerEventLoopMethods {
     type WorkerMsg: QueuedTaskConversion + Send;
+    type ControlMsg;
     type Event;
     fn task_queue(&self) -> &TaskQueue<Self::WorkerMsg>;
-    fn handle_event(&self, event: Self::Event);
+    fn handle_event(&self, event: Self::Event) -> bool;
     fn handle_worker_post_event(&self, worker: &TrustedWorkerAddress) -> Option<AutoWorkerReset>;
+    fn from_control_msg(&self, msg: Self::ControlMsg) -> Self::Event;
     fn from_worker_msg(&self, msg: Self::WorkerMsg) -> Self::Event;
     fn from_devtools_msg(&self, msg: DevtoolScriptControlMsg) -> Self::Event;
+    fn control_receiver(&self) -> &Receiver<Self::ControlMsg>;
 }
 
 // https://html.spec.whatwg.org/multipage/#worker-event-loop
@@ -108,6 +111,7 @@ pub fn run_worker_event_loop<T, WorkerMsg, Event>(
     };
     let task_queue = worker_scope.task_queue();
     let event = select! {
+        recv(worker_scope.control_receiver()) -> msg => worker_scope.from_control_msg(msg.unwrap()),
         recv(task_queue.select()) -> msg => {
             task_queue.take_tasks(msg.unwrap());
             worker_scope.from_worker_msg(task_queue.recv().unwrap())
@@ -136,7 +140,10 @@ pub fn run_worker_event_loop<T, WorkerMsg, Event>(
     }
     // Step 3
     for event in sequential {
-        worker_scope.handle_event(event);
+        if !worker_scope.handle_event(event) {
+            // Shutdown
+            return;
+        }
         // Step 6
         let _ar = match worker {
             Some(worker) => worker_scope.handle_worker_post_event(worker),

components/script/dom/bindings/trace.rs

@@ -135,6 +135,7 @@ use std::path::PathBuf;
 use std::rc::Rc;
 use std::sync::atomic::{AtomicBool, AtomicUsize};
 use std::sync::{Arc, Mutex};
+use std::thread::JoinHandle;
 use std::time::{Instant, SystemTime};
 use style::animation::ElementAnimationSet;
 use style::attr::{AttrIdentifier, AttrValue, LengthOrPercentageOrAuto};
@@ -168,6 +169,7 @@ use webxr_api::SwapChainId as WebXRSwapChainId;
 use webxr_api::{Finger, Hand, Ray, View};
 
 unsafe_no_jsmanaged_fields!(Tm);
+unsafe_no_jsmanaged_fields!(JoinHandle<()>);
 
 /// A trait to allow tracing (only) DOM objects.
 pub unsafe trait JSTraceable {

components/script/dom/dedicatedworkerglobalscope.rs

@@ -56,7 +56,7 @@ use servo_url::ServoUrl;
 use std::mem::replace;
 use std::sync::atomic::AtomicBool;
 use std::sync::Arc;
-use std::thread;
+use std::thread::{self, JoinHandle};
 use style::thread_state::{self, ThreadState};
 
 /// Set the `worker` field of a related DedicatedWorkerGlobalScope object to a particular
@@ -86,6 +86,12 @@ impl<'a> Drop for AutoWorkerReset<'a> {
     }
 }
 
+/// Messages sent from the owning global.
+pub enum DedicatedWorkerControlMsg {
+    /// Shutdown the worker.
+    Exit,
+}
+
 pub enum DedicatedWorkerScriptMsg {
     /// Standard message from a worker.
     CommonWorker(TrustedWorkerAddress, WorkerScriptMsg),
@@ -96,6 +102,7 @@ pub enum DedicatedWorkerScriptMsg {
 pub enum MixedMessage {
     FromWorker(DedicatedWorkerScriptMsg),
     FromDevtools(DevtoolScriptControlMsg),
+    FromControl(DedicatedWorkerControlMsg),
 }
 
 impl QueuedTaskConversion for DedicatedWorkerScriptMsg {
@@ -183,32 +190,45 @@ pub struct DedicatedWorkerGlobalScope {
     #[ignore_malloc_size_of = "Arc"]
     image_cache: Arc<dyn ImageCache>,
     browsing_context: Option<BrowsingContextId>,
+    /// A receiver of control messages,
+    /// currently only used to signal shutdown.
+    #[ignore_malloc_size_of = "Channels are hard"]
+    control_receiver: Receiver<DedicatedWorkerControlMsg>,
 }
 
 impl WorkerEventLoopMethods for DedicatedWorkerGlobalScope {
     type WorkerMsg = DedicatedWorkerScriptMsg;
+    type ControlMsg = DedicatedWorkerControlMsg;
     type Event = MixedMessage;
 
     fn task_queue(&self) -> &TaskQueue<DedicatedWorkerScriptMsg> {
         &self.task_queue
     }
 
-    fn handle_event(&self, event: MixedMessage) {
-        self.handle_mixed_message(event);
+    fn handle_event(&self, event: MixedMessage) -> bool {
+        self.handle_mixed_message(event)
     }
 
     fn handle_worker_post_event(&self, worker: &TrustedWorkerAddress) -> Option<AutoWorkerReset> {
         let ar = AutoWorkerReset::new(&self, worker.clone());
         Some(ar)
     }
 
+    fn from_control_msg(&self, msg: DedicatedWorkerControlMsg) -> MixedMessage {
+        MixedMessage::FromControl(msg)
+    }
+
     fn from_worker_msg(&self, msg: DedicatedWorkerScriptMsg) -> MixedMessage {
         MixedMessage::FromWorker(msg)
     }
 
     fn from_devtools_msg(&self, msg: DevtoolScriptControlMsg) -> MixedMessage {
         MixedMessage::FromDevtools(msg)
     }
+
+    fn control_receiver(&self) -> &Receiver<DedicatedWorkerControlMsg> {
+        &self.control_receiver
+    }
 }
 
 impl DedicatedWorkerGlobalScope {
@@ -226,6 +246,7 @@ impl DedicatedWorkerGlobalScope {
         image_cache: Arc<dyn ImageCache>,
         browsing_context: Option<BrowsingContextId>,
         gpu_id_hub: Arc<Mutex<Identities>>,
+        control_receiver: Receiver<DedicatedWorkerControlMsg>,
     ) -> DedicatedWorkerGlobalScope {
         DedicatedWorkerGlobalScope {
             workerglobalscope: WorkerGlobalScope::new_inherited(
@@ -244,6 +265,7 @@ impl DedicatedWorkerGlobalScope {
             worker: DomRefCell::new(None),
             image_cache: image_cache,
             browsing_context,
+            control_receiver,
         }
     }
 
@@ -262,6 +284,7 @@ impl DedicatedWorkerGlobalScope {
         image_cache: Arc<dyn ImageCache>,
         browsing_context: Option<BrowsingContextId>,
         gpu_id_hub: Arc<Mutex<Identities>>,
+        control_receiver: Receiver<DedicatedWorkerControlMsg>,
     ) -> DomRoot<DedicatedWorkerGlobalScope> {
         let cx = runtime.cx();
         let scope = Box::new(DedicatedWorkerGlobalScope::new_inherited(
@@ -278,6 +301,7 @@ impl DedicatedWorkerGlobalScope {
             image_cache,
             browsing_context,
             gpu_id_hub,
+            control_receiver,
         ));
         unsafe { DedicatedWorkerGlobalScopeBinding::Wrap(SafeJSContext::from_ptr(cx), scope) }
     }
@@ -299,7 +323,8 @@ impl DedicatedWorkerGlobalScope {
         image_cache: Arc<dyn ImageCache>,
         browsing_context: Option<BrowsingContextId>,
         gpu_id_hub: Arc<Mutex<Identities>>,
-    ) {
+        control_receiver: Receiver<DedicatedWorkerControlMsg>,
+    ) -> JoinHandle<()> {
         let serialized_worker_url = worker_url.to_string();
         let name = format!("WebWorker for {}", serialized_worker_url);
         let top_level_browsing_context_id = TopLevelBrowsingContextId::installed();
@@ -370,6 +395,7 @@ impl DedicatedWorkerGlobalScope {
                     image_cache,
                     browsing_context,
                     gpu_id_hub,
+                    control_receiver,
                 );
                 // FIXME(njn): workers currently don't have a unique ID suitable for using in reporter
                 // registration (#6631), so we instead use a random number and cross our fingers.
@@ -434,8 +460,9 @@ impl DedicatedWorkerGlobalScope {
                         parent_sender,
                         CommonScriptMsg::CollectReports,
                     );
+                scope.clear_js_runtime();
             })
-            .expect("Thread spawning failed");
+            .expect("Thread spawning failed")
     }
 
     pub fn image_cache(&self) -> Arc<dyn ImageCache> {
@@ -485,7 +512,7 @@ impl DedicatedWorkerGlobalScope {
         }
     }
 
-    fn handle_mixed_message(&self, msg: MixedMessage) {
+    fn handle_mixed_message(&self, msg: MixedMessage) -> bool {
         // FIXME(#26324): `self.worker` is None in devtools messages.
         match msg {
             MixedMessage::FromDevtools(msg) => match msg {
@@ -505,7 +532,11 @@ impl DedicatedWorkerGlobalScope {
                 self.handle_script_event(msg);
             },
             MixedMessage::FromWorker(DedicatedWorkerScriptMsg::WakeUp) => {},
+            MixedMessage::FromControl(DedicatedWorkerControlMsg::Exit) => {
+                return false;
+            },
         }
+        true
     }
 
     // https://html.spec.whatwg.org/multipage/#runtime-script-errors-2

components/script/dom/globalscope.rs

@@ -26,7 +26,9 @@ use crate::dom::bindings::weakref::{DOMTracker, WeakRef};
 use crate::dom::blob::Blob;
 use crate::dom::broadcastchannel::BroadcastChannel;
 use crate::dom::crypto::Crypto;
-use crate::dom::dedicatedworkerglobalscope::DedicatedWorkerGlobalScope;
+use crate::dom::dedicatedworkerglobalscope::{
+    DedicatedWorkerControlMsg, DedicatedWorkerGlobalScope,
+};
 use crate::dom::errorevent::ErrorEvent;
 use crate::dom::event::{Event, EventBubbles, EventCancelable, EventStatus};
 use crate::dom::eventsource::EventSource;
@@ -65,6 +67,7 @@ use crate::task_source::TaskSourceName;
 use crate::timers::{IsInterval, OneshotTimerCallback, OneshotTimerHandle};
 use crate::timers::{OneshotTimers, TimerCallback};
 use content_security_policy::CspList;
+use crossbeam_channel::Sender;
 use devtools_traits::{PageError, ScriptToDevtoolsControlMsg};
 use dom_struct::dom_struct;
 use embedder_traits::EmbedderMsg;
@@ -112,15 +115,46 @@ use std::ops::Index;
 use std::rc::Rc;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Arc;
+use std::thread::JoinHandle;
 use time::{get_time, Timespec};
 use uuid::Uuid;
 
 #[derive(JSTraceable)]
-pub struct AutoCloseWorker(Arc<AtomicBool>);
+pub struct AutoCloseWorker {
+    /// https://html.spec.whatwg.org/multipage/#dom-workerglobalscope-closing
+    closing: Arc<AtomicBool>,
+    /// A handle to join on the worker thread.
+    join_handle: Option<JoinHandle<()>>,
+    /// A sender of control messages,
+    /// currently only used to signal shutdown.
+    control_sender: Sender<DedicatedWorkerControlMsg>,
+}
 
 impl Drop for AutoCloseWorker {
+    /// <https://html.spec.whatwg.org/multipage/#terminate-a-worker>
     fn drop(&mut self) {
-        self.0.store(true, Ordering::SeqCst);
+        // Step 1.
+        self.closing.store(true, Ordering::SeqCst);
+
+        if self
+            .control_sender
+            .send(DedicatedWorkerControlMsg::Exit)
+            .is_err()
+        {
+            warn!("Couldn't send an exit message to a dedicated worker.");
+        }
+
+        // TODO: step 2 and 3.
+        // Step 4 is unnecessary since we don't use actual ports for dedicated workers.
+        if self
+            .join_handle
+            .take()
+            .expect("No handle to join on worker.")
+            .join()
+            .is_err()
+        {
+            warn!("Failed to join on dedicated worker thread.");
+        }
     }
 }
 
@@ -760,9 +794,18 @@ impl GlobalScope {
     }
 
     /// Remove the routers for ports and broadcast-channels.
-    pub fn remove_web_messaging_infra(&self) {
+    /// Drain the list of workers.
+    pub fn remove_web_messaging_and_dedicated_workers_infra(&self) {
         self.remove_message_ports_router();
         self.remove_broadcast_channel_router();
+
+        // Drop each ref to a worker explicitly now,
+        // which will send a shutdown signal,
+        // and join on the worker thread.
+        self.list_auto_close_worker
+            .borrow_mut()
+            .drain(0..)
+            .for_each(|worker| drop(worker));
     }
 
     /// Update our state to un-managed,
@@ -1794,10 +1837,19 @@ impl GlobalScope {
         &self.permission_state_invocation_results
     }
 
-    pub fn track_worker(&self, closing_worker: Arc<AtomicBool>) {
+    pub fn track_worker(
+        &self,
+        closing: Arc<AtomicBool>,
+        join_handle: JoinHandle<()>,
+        control_sender: Sender<DedicatedWorkerControlMsg>,
+    ) {
         self.list_auto_close_worker
             .borrow_mut()
-            .push(AutoCloseWorker(closing_worker));
+            .push(AutoCloseWorker {
+                closing,
+                join_handle: Some(join_handle),
+                control_sender: control_sender,
+            });
     }
 
     pub fn track_event_source(&self, event_source: &EventSource) {