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Refactor StylesheetLoader so impls do not need to acquire a shared lock.

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This fixes a deadlock:
https://github.com/servo/servo/pull/16014#issuecomment-287527067
This commit is contained in:
Simon Sapin 2017-03-18 13:49:04 +01:00
parent 1bacd0eb15
commit 1e38013783
4 changed files with 84 additions and 59 deletions
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34
ports/geckolib/stylesheet_loader.rs
View file

@ -3,10 +3,10 @@
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
use std::sync::Arc;
use style::gecko::global_style_data::GLOBAL_STYLE_DATA;
use style::gecko_bindings::bindings::Gecko_LoadStyleSheet;
use style::gecko_bindings::structs::{Loader, ServoStyleSheet};
use style::gecko_bindings::sugar::ownership::HasArcFFI;
use style::media_queries::MediaList;
use style::shared_lock::Locked;
use style::stylesheets::{ImportRule, StylesheetLoader as StyleStylesheetLoader};
use style_traits::ToCss;
@ -20,13 +20,12 @@ impl StylesheetLoader {
}
impl StyleStylesheetLoader for StylesheetLoader {
fn request_stylesheet(&self, import_rule: &Arc<Locked<ImportRule>>) {
let global_style_data = &*GLOBAL_STYLE_DATA;
let guard = global_style_data.shared_lock.read();
let import = import_rule.read_with(&guard);
let (spec_bytes, spec_len) = import.url.as_slice_components()
.expect("Import only loads valid URLs");
fn request_stylesheet(
&self,
media: MediaList,
make_import: &mut FnMut(MediaList) -> ImportRule,
make_arc: &mut FnMut(ImportRule) -> Arc<Locked<ImportRule>>,
) -> Arc<Locked<ImportRule>> {
// TODO(emilio): We probably want to share media representation with
// Gecko in Stylo.
//
@ -35,16 +34,27 @@ impl StyleStylesheetLoader for StylesheetLoader {
// evaluate them on the main thread.
//
// Meanwhile, this works.
let media = import.stylesheet.media.read_with(&guard).to_css_string();
let media_string = media.to_css_string();
let import = make_import(media);
// After we get this raw pointer ImportRule will be moved into a lock and Arc
// and so the Arc<Url> pointer inside will also move,
// but the Url it points to or the allocating backing the String inside that Url won’t,
// so this raw pointer will still be valid.
let (spec_bytes, spec_len): (*const u8, usize) = import.url.as_slice_components()
.expect("Import only loads valid URLs");
let arc = make_arc(import);
unsafe {
Gecko_LoadStyleSheet(self.0,
self.1,
HasArcFFI::arc_as_borrowed(import_rule),
HasArcFFI::arc_as_borrowed(&arc),
spec_bytes,
spec_len as u32,
media.as_bytes().as_ptr(),
media.len() as u32);
media_string.as_bytes().as_ptr(),
media_string.len() as u32);
}
arc
}
}