Auto merge of #6795 - pcwalton:display-list-e10s-fixes, r=glennw

Send display lists over IPC in multiprocess mode.

This patch set introduces the `--multiprocess` (`-M`) switch. Right now, all it does it cause display lists to be serialized, but eventually it will cause actual processes to be spawned.

r? @metajack

<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/6795)
<!-- Reviewable:end -->

5 files changed, 105 insertions, 73 deletions

diff --git a/components/util/Cargo.toml b/components/util/Cargo.toml
index a61600c8d5a..6558792b21b 100644
--- a/components/util/Cargo.toml
+++ b/components/util/Cargo.toml
@@ -25,6 +25,9 @@ git = "https://github.com/servo/rust-azure"
 version = "0.3"
 features = [ "serde-serialization" ]
 
+[dependencies.ipc-channel]
+git = "https://github.com/pcwalton/ipc-channel"
+
 [dependencies]
 log = "0.3"
 bitflags = "0.3"
diff --git a/components/util/ipc.rs b/components/util/ipc.rs
new file mode 100644
index 00000000000..7e47ff696f7
--- /dev/null
+++ b/components/util/ipc.rs
@@ -0,0 +1,94 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use opts;
+
+use ipc_channel::ipc::{self, IpcSender};
+use ipc_channel::router::ROUTER;
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+use std::any::Any;
+use std::collections::HashMap;
+use std::sync::Mutex;
+use std::sync::atomic::{ATOMIC_USIZE_INIT, AtomicUsize, Ordering};
+use std::sync::mpsc::{self, Receiver, Sender};
+
+lazy_static! {
+    static ref IN_PROCESS_SENDERS: Mutex<HashMap<usize,Box<Any + Send>>> =
+        Mutex::new(HashMap::new());
+}
+
+static NEXT_SENDER_ID: AtomicUsize = ATOMIC_USIZE_INIT;
+
+pub enum OptionalIpcSender<T> where T: Deserialize + Serialize + Send + Any {
+    OutOfProcess(IpcSender<T>),
+    InProcess(Sender<T>),
+}
+
+impl<T> OptionalIpcSender<T> where T: Deserialize + Serialize + Send + Any {
+    pub fn send(&self, value: T) -> Result<(),()> {
+        match *self {
+            OptionalIpcSender::OutOfProcess(ref ipc_sender) => ipc_sender.send(value),
+            OptionalIpcSender::InProcess(ref sender) => sender.send(value).map_err(|_| ()),
+        }
+    }
+}
+
+impl<T> Clone for OptionalIpcSender<T> where T: Deserialize + Serialize + Send + Any {
+    fn clone(&self) -> OptionalIpcSender<T> {
+        match *self {
+            OptionalIpcSender::OutOfProcess(ref ipc_sender) => {
+                OptionalIpcSender::OutOfProcess((*ipc_sender).clone())
+            }
+            OptionalIpcSender::InProcess(ref sender) => {
+                OptionalIpcSender::InProcess((*sender).clone())
+            }
+        }
+    }
+}
+
+impl<T> Deserialize for OptionalIpcSender<T> where T: Deserialize + Serialize + Send + Any {
+    fn deserialize<D>(deserializer: &mut D)
+                      -> Result<OptionalIpcSender<T>,D::Error> where D: Deserializer {
+        if opts::get().multiprocess {
+            return Ok(OptionalIpcSender::OutOfProcess(try!(Deserialize::deserialize(
+                            deserializer))))
+        }
+        let id: usize = try!(Deserialize::deserialize(deserializer));
+        let sender = (*IN_PROCESS_SENDERS.lock()
+                                         .unwrap()
+                                         .remove(&id)
+                                         .unwrap()
+                                         .downcast_ref::<Sender<T>>()
+                                         .unwrap()).clone();
+        Ok(OptionalIpcSender::InProcess(sender))
+     }
+}
+
+impl<T> Serialize for OptionalIpcSender<T> where T: Deserialize + Serialize + Send + Any {
+    fn serialize<S>(&self, serializer: &mut S) -> Result<(),S::Error> where S: Serializer {
+        match *self {
+            OptionalIpcSender::OutOfProcess(ref ipc_sender) => ipc_sender.serialize(serializer),
+            OptionalIpcSender::InProcess(ref sender) => {
+                let id = NEXT_SENDER_ID.fetch_add(1, Ordering::SeqCst);
+                IN_PROCESS_SENDERS.lock()
+                                  .unwrap()
+                                  .insert(id, Box::new((*sender).clone()) as Box<Any + Send>);
+                id.serialize(serializer)
+            }
+        }
+    }
+}
+
+pub fn optional_ipc_channel<T>() -> (OptionalIpcSender<T>, Receiver<T>)
+                                 where T: Deserialize + Serialize + Send + Any {
+    if opts::get().multiprocess {
+        let (ipc_sender, ipc_receiver) = ipc::channel().unwrap();
+        let receiver = ROUTER.route_ipc_receiver_to_new_mpsc_receiver(ipc_receiver);
+        (OptionalIpcSender::OutOfProcess(ipc_sender), receiver)
+    } else {
+        let (sender, receiver) = mpsc::channel();
+        (OptionalIpcSender::InProcess(sender), receiver)
+    }
+}
+
diff --git a/components/util/lib.rs b/components/util/lib.rs
index b108c516acc..8db4b17f5ec 100644
--- a/components/util/lib.rs
+++ b/components/util/lib.rs
@@ -31,6 +31,7 @@ extern crate alloc;
 #[macro_use] extern crate cssparser;
 extern crate euclid;
 extern crate getopts;
+extern crate ipc_channel;
 extern crate libc;
 extern crate num as num_lib;
 extern crate num_cpus;
@@ -49,6 +50,7 @@ pub mod debug_utils;
 pub mod deque;
 pub mod linked_list;
 pub mod geometry;
+pub mod ipc;
 pub mod logical_geometry;
 pub mod mem;
 pub mod opts;
diff --git a/components/util/linked_list.rs b/components/util/linked_list.rs
index bf20f434d54..5114f02c0e4 100644
--- a/components/util/linked_list.rs
+++ b/components/util/linked_list.rs
@@ -4,81 +4,8 @@
 
 //! Utility functions for doubly-linked lists.
 
-use mem::HeapSizeOf;
-
-use serde::de::{Error, SeqVisitor, Visitor};
-use serde::ser::impls::SeqIteratorVisitor;
-use serde::{Deserialize, Deserializer, Serialize, Serializer};
 use std::collections::LinkedList;
-use std::marker::PhantomData;
 use std::mem;
-use std::ops::{Deref, DerefMut};
-
-pub struct SerializableLinkedList<T>(LinkedList<T>);
-
-impl<T> SerializableLinkedList<T> {
-    pub fn new(linked_list: LinkedList<T>) -> SerializableLinkedList<T> {
-        SerializableLinkedList(linked_list)
-    }
-}
-
-impl<T> Deref for SerializableLinkedList<T> {
-    type Target = LinkedList<T>;
-
-    fn deref(&self) -> &LinkedList<T> {
-        &self.0
-    }
-}
-
-impl<T> DerefMut for SerializableLinkedList<T> {
-    fn deref_mut(&mut self) -> &mut LinkedList<T> {
-        &mut self.0
-    }
-}
-
-impl<T: HeapSizeOf> HeapSizeOf for SerializableLinkedList<T> {
-    fn heap_size_of_children(&self) -> usize {
-        self.0.heap_size_of_children()
-    }
-}
-
-impl<T> Serialize for SerializableLinkedList<T> where T: Serialize {
-    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error> where S: Serializer {
-        serializer.visit_seq(SeqIteratorVisitor::new(self.0.iter(), Some(self.0.len())))
-    }
-}
-
-impl<T> Deserialize for SerializableLinkedList<T> where T: Deserialize {
-    fn deserialize<D>(deserializer: &mut D) -> Result<SerializableLinkedList<T>, D::Error>
-                      where D: Deserializer {
-        struct SerializableLinkedListVisitor<T> {
-            marker: PhantomData<T>,
-        }
-
-        impl<T> Visitor for SerializableLinkedListVisitor<T> where T: Deserialize {
-            type Value = SerializableLinkedList<T>;
-
-            #[inline]
-            fn visit_seq<V>(&mut self, mut visitor: V)
-                            -> Result<SerializableLinkedList<T>, V::Error>
-                            where V: SeqVisitor {
-                let mut list = LinkedList::new();
-                for _ in 0..visitor.size_hint().0 {
-                    match try!(visitor.visit()) {
-                        Some(element) => list.push_back(element),
-                        None => return Err(Error::end_of_stream_error()),
-                    }
-                }
-                try!(visitor.end());
-                Ok(SerializableLinkedList(list))
-            }
-        }
-
-        deserializer.visit_seq(SerializableLinkedListVisitor {
-            marker: PhantomData,
-        })
-    }
-}
 
 /// Splits the head off a list in O(1) time, and returns the head.
 pub fn split_off_head<T>(list: &mut LinkedList<T>) -> LinkedList<T> {
diff --git a/components/util/opts.rs b/components/util/opts.rs
index c8f65c97e54..efc580bd5e6 100644
--- a/components/util/opts.rs
+++ b/components/util/opts.rs
@@ -132,6 +132,9 @@ pub struct Opts {
     /// An optional string allowing the user agent to be set for testing.
     pub user_agent: Option<String>,
 
+    /// Whether to run in multiprocess mode.
+    pub multiprocess: bool,
+
     /// Dumps the flow tree after a layout.
     pub dump_flow_tree: bool,
 
@@ -251,6 +254,7 @@ pub fn default_opts() -> Opts {
         webdriver_port: None,
         initial_window_size: Size2D::typed(800, 600),
         user_agent: None,
+        multiprocess: false,
         dump_flow_tree: false,
         dump_display_list: false,
         dump_display_list_json: false,
@@ -291,6 +295,7 @@ pub fn from_cmdline_args(args: &[String]) {
         getopts::optflagopt("", "webdriver", "Start remote WebDriver server on port", "7000"),
         getopts::optopt("", "resolution", "Set window resolution.", "800x600"),
         getopts::optopt("u", "user-agent", "Set custom user agent string", "NCSA Mosaic/1.0 (X11;SunOS 4.1.4 sun4m)"),
+        getopts::optflag("M", "multiprocess", "Run in multiprocess mode"),
         getopts::optopt("Z", "debug",
                         "A comma-separated string of debug options. Pass help to show available options.", ""),
         getopts::optflag("h", "help", "Print this message"),
@@ -421,6 +426,7 @@ pub fn from_cmdline_args(args: &[String]) {
         webdriver_port: webdriver_port,
         initial_window_size: initial_window_size,
         user_agent: opt_match.opt_str("u"),
+        multiprocess: opt_match.opt_present("M"),
         show_debug_borders: debug_options.contains(&"show-compositor-borders"),
         show_debug_fragment_borders: debug_options.contains(&"show-fragment-borders"),
         show_debug_parallel_paint: debug_options.contains(&"show-parallel-paint"),