GenericChannel: Migrate compositor channels to GenericChannel (#38782)

Besides migrating the channel to GenericChannel, this PR adds
`routed_channel_with_local_sender()` to `generic_channel`. This is for
existing use-cases, where we want to provide both an IPC capable
GenericSender, as well as a crossbeam Sender, for efficient sending if
the sender is in the same process.

Testing: All of our channels should send / receive at least some
messages during WPT tests.

Signed-off-by: Jonathan Schwender <schwenderjonathan@gmail.com>

components/compositing/compositor.rs

@@ -11,9 +11,9 @@ use std::rc::Rc;
 use std::sync::Arc;
 use std::time::{SystemTime, UNIX_EPOCH};
 
-use base::Epoch;
 use base::cross_process_instant::CrossProcessInstant;
 use base::id::{PipelineId, WebViewId};
+use base::{Epoch, generic_channel};
 use bitflags::bitflags;
 use compositing_traits::display_list::{CompositorDisplayListInfo, ScrollTree, ScrollType};
 use compositing_traits::rendering_context::RenderingContext;
@@ -22,7 +22,7 @@ use compositing_traits::{
     WebViewTrait,
 };
 use constellation_traits::{EmbedderToConstellationMessage, PaintMetricEvent};
-use crossbeam_channel::{Receiver, Sender};
+use crossbeam_channel::Sender;
 use dpi::PhysicalSize;
 use embedder_traits::{CompositorHitTestResult, InputEvent, ShutdownState, ViewportDetails};
 use euclid::{Point2D, Rect, Scale, Size2D, Transform3D};
@@ -90,7 +90,7 @@ pub struct ServoRenderer {
     shutdown_state: Rc<Cell<ShutdownState>>,
 
     /// The port on which we receive messages.
-    compositor_receiver: Receiver<CompositorMsg>,
+    compositor_receiver: generic_channel::RoutedReceiver<CompositorMsg>,
 
     /// The channel on which messages can be sent to the constellation.
     pub(crate) constellation_sender: Sender<EmbedderToConstellationMessage>,
@@ -1377,7 +1377,7 @@ impl IOCompositor {
     }
 
     /// Get the message receiver for this [`IOCompositor`].
-    pub fn receiver(&self) -> Ref<'_, Receiver<CompositorMsg>> {
+    pub fn receiver(&self) -> Ref<'_, generic_channel::RoutedReceiver<CompositorMsg>> {
         Ref::map(self.global.borrow(), |global| &global.compositor_receiver)
     }
 

components/compositing/lib.rs

@@ -7,10 +7,11 @@
 use std::cell::Cell;
 use std::rc::Rc;
 
+use base::generic_channel;
 use compositing_traits::rendering_context::RenderingContext;
 use compositing_traits::{CompositorMsg, CompositorProxy};
 use constellation_traits::EmbedderToConstellationMessage;
-use crossbeam_channel::{Receiver, Sender};
+use crossbeam_channel::Sender;
 use embedder_traits::{EventLoopWaker, ShutdownState};
 use profile_traits::{mem, time};
 use webrender::RenderApi;
@@ -32,7 +33,7 @@ pub struct InitialCompositorState {
     /// A channel to the compositor.
     pub sender: CompositorProxy,
     /// A port on which messages inbound to the compositor can be received.
-    pub receiver: Receiver<CompositorMsg>,
+    pub receiver: generic_channel::RoutedReceiver<CompositorMsg>,
     /// A channel to the constellation.
     pub constellation_chan: Sender<EmbedderToConstellationMessage>,
     /// A channel to the time profiler thread.

components/constellation/constellation.rs

@@ -99,11 +99,12 @@ use background_hang_monitor::HangMonitorRegister;
 use background_hang_monitor_api::{
     BackgroundHangMonitorControlMsg, BackgroundHangMonitorRegister, HangMonitorAlert,
 };
-use base::Epoch;
+use base::generic_channel::GenericSender;
 use base::id::{
     BrowsingContextGroupId, BrowsingContextId, HistoryStateId, MessagePortId, MessagePortRouterId,
     PipelineId, PipelineNamespace, PipelineNamespaceId, PipelineNamespaceRequest, WebViewId,
 };
+use base::{Epoch, generic_channel};
 #[cfg(feature = "bluetooth")]
 use bluetooth_traits::BluetoothRequest;
 use canvas::canvas_paint_thread::CanvasPaintThread;
@@ -288,11 +289,11 @@ pub struct Constellation<STF, SWF> {
 
     /// An IPC channel for script threads to send messages to the constellation.
     /// This is the script threads' view of `script_receiver`.
-    script_sender: IpcSender<(PipelineId, ScriptToConstellationMessage)>,
+    script_sender: GenericSender<(PipelineId, ScriptToConstellationMessage)>,
 
     /// A channel for the constellation to receive messages from script threads.
     /// This is the constellation's view of `script_sender`.
-    script_receiver: Receiver<Result<(PipelineId, ScriptToConstellationMessage), IpcError>>,
+    script_receiver: generic_channel::RoutedReceiver<(PipelineId, ScriptToConstellationMessage)>,
 
     /// A handle to register components for hang monitoring.
     /// None when in multiprocess mode.
@@ -605,11 +606,8 @@ where
             .name("Constellation".to_owned())
             .spawn(move || {
                 let (script_ipc_sender, script_ipc_receiver) =
-                    ipc::channel().expect("ipc channel failure");
+                    generic_channel::channel().expect("ipc channel failure");
-                let script_receiver =
+                let script_receiver = script_ipc_receiver.route_preserving_errors();
-                    route_ipc_receiver_to_new_crossbeam_receiver_preserving_errors(
-                        script_ipc_receiver,
-                    );
 
                 let (namespace_ipc_sender, namespace_ipc_receiver) =
                     ipc::channel().expect("ipc channel failure");
@@ -1243,7 +1241,7 @@ where
 
         let request = match request {
             Ok(request) => request,
-            Err(err) => return error!("Deserialization failed ({}).", err),
+            Err(err) => return error!("Deserialization failed ({err:?})."),
         };
 
         match request {

components/script/dom/workletglobalscope.rs

@@ -4,6 +4,7 @@
 
 use std::sync::Arc;
 
+use base::generic_channel::GenericSender;
 use base::id::PipelineId;
 use constellation_traits::{ScriptToConstellationChan, ScriptToConstellationMessage};
 use crossbeam_channel::Sender;
@@ -199,7 +200,7 @@ pub(crate) struct WorkletGlobalScopeInit {
     /// Channel to devtools
     pub(crate) devtools_chan: Option<IpcSender<ScriptToDevtoolsControlMsg>>,
     /// Messages to send to constellation
-    pub(crate) to_constellation_sender: IpcSender<(PipelineId, ScriptToConstellationMessage)>,
+    pub(crate) to_constellation_sender: GenericSender<(PipelineId, ScriptToConstellationMessage)>,
     /// The image cache
     pub(crate) image_cache: Arc<dyn ImageCache>,
     /// Identity manager for WebGPU resources

components/script/messaging.rs

@@ -340,7 +340,7 @@ pub(crate) struct ScriptThreadSenders {
     /// particular pipelines.
     #[no_trace]
     pub(crate) pipeline_to_constellation_sender:
-        IpcSender<(PipelineId, ScriptToConstellationMessage)>,
+        GenericSender<(PipelineId, ScriptToConstellationMessage)>,
 
     /// The shared [`IpcSender`] which is sent to the `ImageCache` when requesting an image. The
     /// messages on this channel are routed to crossbeam [`Sender`] on the router thread, which

components/servo/lib.rs

@@ -33,6 +33,7 @@ use std::rc::{Rc, Weak};
 use std::sync::{Arc, Mutex};
 use std::thread;
 
+use base::generic_channel;
 pub use base::id::WebViewId;
 use base::id::{PipelineNamespace, PipelineNamespaceId};
 #[cfg(feature = "bluetooth")]
@@ -82,7 +83,6 @@ use gaol::sandbox::{ChildSandbox, ChildSandboxMethods};
 pub use gleam::gl;
 use gleam::gl::RENDERER;
 use ipc_channel::ipc::{self, IpcSender};
-use ipc_channel::router::ROUTER;
 use javascript_evaluator::JavaScriptEvaluator;
 pub use keyboard_types::{
     Code, CompositionEvent, CompositionState, Key, KeyState, Location, Modifiers, NamedKey,
@@ -543,7 +543,7 @@ impl Servo {
             let mut compositor = self.compositor.borrow_mut();
             let mut messages = Vec::new();
             while let Ok(message) = compositor.receiver().try_recv() {
-                messages.push(message);
+                messages.push(message.expect("IPC serialization error"));
             }
             compositor.handle_messages(messages);
         }
@@ -1094,28 +1094,23 @@ fn create_embedder_channel(
 
 fn create_compositor_channel(
     event_loop_waker: Box<dyn EventLoopWaker>,
-) -> (CompositorProxy, Receiver<CompositorMsg>) {
+) -> (
-    let (sender, receiver) = unbounded();
+    CompositorProxy,
+    generic_channel::RoutedReceiver<CompositorMsg>,
+) {
+    let routed_channel =
+        generic_channel::routed_channel_with_local_sender().expect("Create channel failure");
 
-    let (compositor_ipc_sender, compositor_ipc_receiver) =
+    let cross_process_compositor_api =
-        ipc::channel().expect("ipc channel failure");
+        CrossProcessCompositorApi(routed_channel.generic_sender.clone());
 
-    let cross_process_compositor_api = CrossProcessCompositorApi(compositor_ipc_sender);
+    let compositor_proxy = CompositorProxy::new(
-    let compositor_proxy = CompositorProxy {
+        routed_channel.local_sender,
-        sender,
         cross_process_compositor_api,
         event_loop_waker,
-    };
-
-    let compositor_proxy_clone = compositor_proxy.clone();
-    ROUTER.add_typed_route(
-        compositor_ipc_receiver,
-        Box::new(move |message| {
-            compositor_proxy_clone.send(message.expect("Could not convert Compositor message"));
-        }),
     );
 
-    (compositor_proxy, receiver)
+    (compositor_proxy, routed_channel.local_receiver)
 }
 
 #[allow(clippy::too_many_arguments)]

components/shared/base/generic_channel.rs

@@ -395,6 +395,18 @@ where
     }
 }
 
+/// A GenericChannel, which was routed via the Router.
+pub struct GenericRoutedChannel<T: Serialize + for<'de> Deserialize<'de>> {
+    /// A GenericSender of the channel, i.e. it may be sent to other processes in multiprocess mode.
+    /// Connected to `local_receiver` via the [ROUTER].
+    pub generic_sender: GenericSender<T>,
+    /// A sender that directly sends to the local_receiver. Can only be used in the same process
+    /// as the `local_receiver`.
+    pub local_sender: crossbeam_channel::Sender<Result<T, ipc_channel::Error>>,
+    /// The receiving end of the channel. Only usable in the current process.
+    pub local_receiver: RoutedReceiver<T>,
+}
+
 /// Private helper function to create a crossbeam based channel.
 ///
 /// Do NOT make this function public!
@@ -435,6 +447,34 @@ where
     }
 }
 
+/// Returns a [GenericRoutedChannel], where the receiver is usable in the current process,
+/// and sending is possible both in remote and local process, via the generic_sender and the
+/// local_sender.
+pub fn routed_channel_with_local_sender<T>() -> Option<GenericRoutedChannel<T>>
+where
+    T: for<'de> Deserialize<'de> + Serialize + Send + 'static,
+{
+    let (crossbeam_sender, crossbeam_receiver) = crossbeam_channel::unbounded();
+    let generic_sender = if opts::get().multiprocess || opts::get().force_ipc {
+        let (ipc_sender, ipc_receiver) = ipc_channel::ipc::channel().ok()?;
+        let crossbeam_sender_clone = crossbeam_sender.clone();
+        ROUTER.add_typed_route(
+            ipc_receiver,
+            Box::new(move |message| {
+                let _ = crossbeam_sender_clone.send(message);
+            }),
+        );
+        GenericSender(GenericSenderVariants::Ipc(ipc_sender))
+    } else {
+        GenericSender(GenericSenderVariants::Crossbeam(crossbeam_sender.clone()))
+    };
+    Some(GenericRoutedChannel {
+        generic_sender,
+        local_sender: crossbeam_sender,
+        local_receiver: crossbeam_receiver,
+    })
+}
+
 #[cfg(test)]
 mod single_process_channel_tests {
     //! These unit-tests test that ipc_channel and crossbeam_channel Senders and Receivers

components/shared/compositing/lib.rs

@@ -23,6 +23,7 @@ pub mod viewport_description;
 use std::collections::HashMap;
 use std::sync::{Arc, Mutex};
 
+use base::generic_channel::GenericSender;
 use bitflags::bitflags;
 use display_list::CompositorDisplayListInfo;
 use embedder_traits::ScreenGeometry;
@@ -44,7 +45,12 @@ use crate::viewport_description::ViewportDescription;
 /// Sends messages to the compositor.
 #[derive(Clone)]
 pub struct CompositorProxy {
-    pub sender: Sender<CompositorMsg>,
+    /// A sender optimised for sending in the local process.
+    /// The type is a Result to match the API of ipc_channel after routing,
+    /// which contains a Result to propagate deserialization errors to the
+    /// recipient.
+    /// The field is private to hide the inner `Result` type.
+    sender: Sender<Result<CompositorMsg, ipc_channel::Error>>,
     /// Access to [`Self::sender`] that is possible to send across an IPC
     /// channel. These messages are routed via the router thread to
     /// [`Self::sender`].
@@ -52,6 +58,20 @@ pub struct CompositorProxy {
     pub event_loop_waker: Box<dyn EventLoopWaker>,
 }
 
+impl CompositorProxy {
+    pub fn new(
+        local_process_sender: Sender<Result<CompositorMsg, ipc_channel::Error>>,
+        cross_process_compositor_api: CrossProcessCompositorApi,
+        event_loop_waker: Box<dyn EventLoopWaker>,
+    ) -> Self {
+        Self {
+            sender: local_process_sender,
+            cross_process_compositor_api,
+            event_loop_waker,
+        }
+    }
+}
+
 impl OpaqueSender<CompositorMsg> for CompositorProxy {
     fn send(&self, message: CompositorMsg) {
         CompositorProxy::send(self, message)
@@ -60,7 +80,7 @@ impl OpaqueSender<CompositorMsg> for CompositorProxy {
 
 impl CompositorProxy {
     pub fn send(&self, msg: CompositorMsg) {
-        if let Err(err) = self.sender.send(msg) {
+        if let Err(err) = self.sender.send(Ok(msg)) {
             warn!("Failed to send response ({:?}).", err);
         }
         self.event_loop_waker.wake();
@@ -170,18 +190,18 @@ pub struct CompositionPipeline {
 
 /// A mechanism to send messages from ScriptThread to the parent process' WebRender instance.
 #[derive(Clone, Deserialize, MallocSizeOf, Serialize)]
-pub struct CrossProcessCompositorApi(pub IpcSender<CompositorMsg>);
+pub struct CrossProcessCompositorApi(pub GenericSender<CompositorMsg>);
 
 impl CrossProcessCompositorApi {
     /// Create a new [`CrossProcessCompositorApi`] struct that does not have a listener on the other
     /// end to use for unit testing.
     pub fn dummy() -> Self {
-        let (sender, _) = ipc::channel().unwrap();
+        let (sender, _) = base::generic_channel::channel().unwrap();
         Self(sender)
     }
 
     /// Get the sender for this proxy.
-    pub fn sender(&self) -> &IpcSender<CompositorMsg> {
+    pub fn sender(&self) -> &GenericSender<CompositorMsg> {
         &self.0
     }
 

components/shared/constellation/from_script_message.rs

@@ -8,6 +8,7 @@ use std::collections::HashMap;
 use std::fmt;
 
 use base::Epoch;
+use base::generic_channel::{GenericSender, SendResult};
 use base::id::{
     BroadcastChannelRouterId, BrowsingContextId, HistoryStateId, MessagePortId,
     MessagePortRouterId, PipelineId, ServiceWorkerId, ServiceWorkerRegistrationId, WebViewId,
@@ -21,7 +22,6 @@ use embedder_traits::{
 };
 use euclid::default::Size2D as UntypedSize2D;
 use http::{HeaderMap, Method};
-use ipc_channel::Error as IpcError;
 use ipc_channel::ipc::{IpcReceiver, IpcSender};
 use malloc_size_of_derive::MallocSizeOf;
 use net_traits::policy_container::PolicyContainer;
@@ -46,14 +46,14 @@ use crate::{
 #[derive(Clone, Debug, Deserialize, MallocSizeOf, Serialize)]
 pub struct ScriptToConstellationChan {
     /// Sender for communicating with constellation thread.
-    pub sender: IpcSender<(PipelineId, ScriptToConstellationMessage)>,
+    pub sender: GenericSender<(PipelineId, ScriptToConstellationMessage)>,
     /// Used to identify the origin of the message.
     pub pipeline_id: PipelineId,
 }
 
 impl ScriptToConstellationChan {
     /// Send ScriptMsg and attach the pipeline_id to the message.
-    pub fn send(&self, msg: ScriptToConstellationMessage) -> Result<(), IpcError> {
+    pub fn send(&self, msg: ScriptToConstellationMessage) -> SendResult {
         self.sender.send((self.pipeline_id, msg))
     }
 }