add mechanism to join on service- and dedicated-worker threads

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};
@@ -167,6 +168,7 @@ 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
@@ -299,7 +299,7 @@ impl DedicatedWorkerGlobalScope {
         image_cache: Arc<dyn ImageCache>,
         browsing_context: Option<BrowsingContextId>,
         gpu_id_hub: Arc<Mutex<Identities>>,
-    ) {
+    ) -> 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();
@@ -435,7 +435,7 @@ impl DedicatedWorkerGlobalScope {
                         CommonScriptMsg::CollectReports,
                     );
             })
-            .expect("Thread spawning failed");
+            .expect("Thread spawning failed")
     }
 
     pub fn image_cache(&self) -> Arc<dyn ImageCache> {

components/script/dom/globalscope.rs

@@ -112,15 +112,29 @@ 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 {
+    closing: Arc<AtomicBool>,
+    join_handle: Option<JoinHandle<()>>,
+}
 
 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);
+
+        // TODO: step 2 and 3.
+        // Step 4 is unnecessary since we don't use actual ports for dedicated workers.
+        self.join_handle
+            .take()
+            .expect("No handle to join on worker.")
+            .join()
+            .expect("Couldn't join on worker thread.");
     }
 }
 
@@ -1794,10 +1808,13 @@ 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<()>) {
         self.list_auto_close_worker
             .borrow_mut()
-            .push(AutoCloseWorker(closing_worker));
+            .push(AutoCloseWorker {
+                closing,
+                join_handle: Some(join_handle),
+            });
     }
 
     pub fn track_event_source(&self, event_source: &EventSource) {

components/script/dom/serviceworkerglobalscope.rs

@@ -45,7 +45,7 @@ use servo_config::pref;
 use servo_rand::random;
 use servo_url::ServoUrl;
 use std::sync::Arc;
-use std::thread;
+use std::thread::{self, JoinHandle};
 use std::time::{Duration, Instant};
 use style::thread_state::{self, ThreadState};
 
@@ -259,7 +259,7 @@ impl ServiceWorkerGlobalScope {
         devtools_receiver: IpcReceiver<DevtoolScriptControlMsg>,
         swmanager_sender: IpcSender<ServiceWorkerMsg>,
         scope_url: ServoUrl,
-    ) {
+    ) -> JoinHandle<()> {
         let ScopeThings {
             script_url,
             init,
@@ -361,7 +361,7 @@ impl ServiceWorkerGlobalScope {
                     );
                 scope.clear_js_runtime();
             })
-            .expect("Thread spawning failed");
+            .expect("Thread spawning failed")
     }
 
     fn handle_mixed_message(&self, msg: MixedMessage) -> bool {

components/script/dom/worker.rs

@@ -87,7 +87,6 @@ impl Worker {
         let (sender, receiver) = unbounded();
         let closing = Arc::new(AtomicBool::new(false));
         let worker = Worker::new(global, sender.clone(), closing.clone());
-        global.track_worker(closing.clone());
         let worker_ref = Trusted::new(&*worker);
 
         let worker_load_origin = WorkerScriptLoadOrigin {
@@ -125,7 +124,7 @@ impl Worker {
 
         let init = prepare_workerscope_init(global, Some(devtools_sender), Some(worker_id));
 
-        DedicatedWorkerGlobalScope::run_worker_scope(
+        let join_handle = DedicatedWorkerGlobalScope::run_worker_scope(
             init,
             worker_url,
             devtools_receiver,
@@ -136,12 +135,14 @@ impl Worker {
             worker_load_origin,
             String::from(&*worker_options.name),
             worker_options.type_,
-            closing,
+            closing.clone(),
             global.image_cache(),
             browsing_context,
             global.wgpu_id_hub(),
         );
 
+        global.track_worker(closing, join_handle);
+
         Ok(worker)
     }