Auto merge of #18566 - bholley:thread_state_fixes, r=Manishearth

Thread state fixes

https://bugzilla.mozilla.org/show_bug.cgi?id=1400435

components/layout_thread/lib.rs

@@ -461,7 +461,8 @@ impl LayoutThread {
             ScaleFactor::new(opts::get().device_pixels_per_px.unwrap_or(1.0)));
 
         let configuration =
-            rayon::Configuration::new().num_threads(layout_threads);
+            rayon::Configuration::new().num_threads(layout_threads)
+                                       .start_handler(|_| thread_state::initialize_layout_worker_thread());
         let parallel_traversal = if layout_threads > 1 {
             Some(rayon::ThreadPool::new(configuration).expect("ThreadPool creation failed"))
         } else {

components/style/gecko/global_style_data.rs

@@ -15,6 +15,7 @@ use shared_lock::SharedRwLock;
 use std::cmp;
 use std::env;
 use std::ffi::CString;
+use thread_state;
 
 /// Global style data
 pub struct GlobalStyleData {
@@ -39,6 +40,7 @@ fn thread_name(index: usize) -> String {
 }
 
 fn thread_startup(index: usize) {
+    thread_state::initialize_layout_worker_thread();
     unsafe {
         Gecko_SetJemallocThreadLocalArena(true);
     }

components/style/thread_state.rs

@@ -2,15 +2,12 @@
  * 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/. */
 
-//! Supports dynamic assertions in debug builds about what sort of thread is
+//! Supports dynamic assertions in about what sort of thread is running and
-//! running and what state it's in.
+//! what state it's in.
-//!
-//! In release builds, `get` returns 0.  All of the other functions inline
-//! away to nothing.
 
 #![deny(missing_docs)]
 
-pub use self::imp::{enter, exit, get, initialize};
+use std::cell::RefCell;
 
 bitflags! {
     /// A thread state flag, used for multiple assertions.
@@ -37,22 +34,12 @@ macro_rules! thread_types ( ( $( $fun:ident = $flag:ident ; )* ) => (
         }
 
         $(
-            #[cfg(debug_assertions)]
             #[allow(missing_docs)]
             pub fn $fun(self) -> bool {
                 self.contains($flag)
             }
-            #[cfg(not(debug_assertions))]
-            #[allow(missing_docs)]
-            pub fn $fun(self) -> bool {
-                true
-            }
         )*
     }
-
-    #[cfg(debug_assertions)]
-    static TYPES: &'static [ThreadState] =
-        &[ $( $flag ),* ];
 ));
 
 thread_types! {
@@ -60,14 +47,9 @@ thread_types! {
     is_layout = LAYOUT;
 }
 
-#[cfg(debug_assertions)]
-mod imp {
-    use std::cell::RefCell;
-    use super::{TYPES, ThreadState};
-
 thread_local!(static STATE: RefCell<Option<ThreadState>> = RefCell::new(None));
 
-    /// Initialize the current thread state.
+/// Initializes the current thread state.
 pub fn initialize(x: ThreadState) {
     STATE.with(|ref k| {
         if let Some(ref s) = *k.borrow() {
@@ -75,49 +57,39 @@ mod imp {
         }
         *k.borrow_mut() = Some(x);
     });
-        get(); // check the assertion below
 }
 
-    /// Get the current thread state.
+/// Initializes the current thread as a layout worker thread.
+pub fn initialize_layout_worker_thread() {
+    initialize(LAYOUT | IN_WORKER);
+}
+
+/// Gets the current thread state.
 pub fn get() -> ThreadState {
     let state = STATE.with(|ref k| {
         match *k.borrow() {
-                // This is one of the layout threads, that use rayon.
+            None => ThreadState::empty(), // Unknown thread.
-                None => super::LAYOUT | super::IN_WORKER,
             Some(s) => s,
         }
     });
 
-        // Exactly one of the thread type flags should be set.
-        assert_eq!(1, TYPES.iter().filter(|&&ty| state.contains(ty)).count());
     state
 }
 
-    /// Enter into a given temporary state. Panics if re-entring.
+/// Enters into a given temporary state. Panics if re-entring.
 pub fn enter(x: ThreadState) {
     let state = get();
-        assert!(!state.intersects(x));
+    debug_assert!(!state.intersects(x));
     STATE.with(|ref k| {
         *k.borrow_mut() = Some(state | x);
     })
 }
 
-    /// Exit a given temporary state.
+/// Exits a given temporary state.
 pub fn exit(x: ThreadState) {
     let state = get();
-        assert!(state.contains(x));
+    debug_assert!(state.contains(x));
     STATE.with(|ref k| {
         *k.borrow_mut() = Some(state & !x);
     })
 }
-}
-
-#[cfg(not(debug_assertions))]
-#[allow(missing_docs)]
-mod imp {
-    use super::ThreadState;
-    #[inline(always)] pub fn initialize(_: ThreadState) { }
-    #[inline(always)] pub fn get() -> ThreadState { ThreadState::empty() }
-    #[inline(always)] pub fn enter(_: ThreadState) { }
-    #[inline(always)] pub fn exit(_: ThreadState) { }
-}