fune/servo/components/script/dom/cssnamespacerule.rs
Simon Sapin 33a9e6d050 servo: Merge #16014 - Per-process lock for CSSOM objects (from servo:style-ref); r=emilio
<!-- Please describe your changes on the following line: -->

Before this PR, every object reflected in CSSOM is in `Arc<RwLock<_>>` to enable safe (synchronized) mutable aliasing. Acquiring all these locks has significant cost during selector matching:

* https://bugzilla.mozilla.org/show_bug.cgi?id=1311469
* https://bugzilla.mozilla.org/show_bug.cgi?id=1335941
* https://bugzilla.mozilla.org/show_bug.cgi?id=1339703

This PR introduce a mechanism to protect many objects with the same `RwLock` that only needs to be acquired once.

In Stylo, there is one such lock per process (in a `lazy_static`), used for everything.

I non-Stylo Servo, I originally intended to have one such lock per document (for author-origin stylesheets, and one per process for user-agent and user sytlesheets since they’re shared across documents, and never mutated anyway). However I failed to have the same document-specific (or pipeline-specific) `Arc` reachable from both `Document` nodes and `LayoutThread`. Recursively following callers lead me to include this `Arc` in `UnprivilegedPipelineContent`, but that needs to be serializable. So there is a second process-wide lock.

This was previously #15998, closed accidentally.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

<!-- Either: -->
- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

Source-Repo: https://github.com/servo/servo
Source-Revision: bb54f0a429de0e8b8861f8071b6cf82f73622664

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : 851230e57ac8775707df5f0f103be5feac81fc41
2017-03-19 14:31:19 -07:00

69 lines
2.5 KiB
Rust

/* 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 dom::bindings::codegen::Bindings::CSSNamespaceRuleBinding;
use dom::bindings::codegen::Bindings::CSSNamespaceRuleBinding::CSSNamespaceRuleMethods;
use dom::bindings::js::Root;
use dom::bindings::reflector::reflect_dom_object;
use dom::bindings::str::DOMString;
use dom::cssrule::{CSSRule, SpecificCSSRule};
use dom::cssstylesheet::CSSStyleSheet;
use dom::window::Window;
use dom_struct::dom_struct;
use std::sync::Arc;
use style::shared_lock::{Locked, ToCssWithGuard};
use style::stylesheets::NamespaceRule;
#[dom_struct]
pub struct CSSNamespaceRule {
cssrule: CSSRule,
#[ignore_heap_size_of = "Arc"]
namespacerule: Arc<Locked<NamespaceRule>>,
}
impl CSSNamespaceRule {
fn new_inherited(parent_stylesheet: &CSSStyleSheet, namespacerule: Arc<Locked<NamespaceRule>>)
-> CSSNamespaceRule {
CSSNamespaceRule {
cssrule: CSSRule::new_inherited(parent_stylesheet),
namespacerule: namespacerule,
}
}
#[allow(unrooted_must_root)]
pub fn new(window: &Window, parent_stylesheet: &CSSStyleSheet,
namespacerule: Arc<Locked<NamespaceRule>>) -> Root<CSSNamespaceRule> {
reflect_dom_object(box CSSNamespaceRule::new_inherited(parent_stylesheet, namespacerule),
window,
CSSNamespaceRuleBinding::Wrap)
}
}
impl CSSNamespaceRuleMethods for CSSNamespaceRule {
// https://drafts.csswg.org/cssom/#dom-cssnamespacerule-prefix
fn Prefix(&self) -> DOMString {
let guard = self.cssrule.shared_lock().read();
self.namespacerule.read_with(&guard).prefix
.as_ref().map(|s| s.to_string().into())
.unwrap_or(DOMString::new())
}
// https://drafts.csswg.org/cssom/#dom-cssnamespacerule-namespaceuri
fn NamespaceURI(&self) -> DOMString {
let guard = self.cssrule.shared_lock().read();
(*self.namespacerule.read_with(&guard).url).into()
}
}
impl SpecificCSSRule for CSSNamespaceRule {
fn ty(&self) -> u16 {
use dom::bindings::codegen::Bindings::CSSRuleBinding::CSSRuleConstants;
CSSRuleConstants::NAMESPACE_RULE
}
fn get_css(&self) -> DOMString {
let guard = self.cssrule.shared_lock().read();
self.namespacerule.read_with(&guard).to_css_string(&guard).into()
}
}