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Layout-2020: Serialize access to stylo thread pool.

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When rendering a page containing an iframe, layout 2020
creates parallel 'Layout' threads which share workers
in the stylo thread pool.

Because of the way the 'StyleSharingCache' is designed
using TLS for storage of the LRU cache, this leads to
a double borrow of the cache when both layout threads
run concurrently.

More details about the issue can be found here:
https://gist.github.com/mukilan/ed57eb61b83237a05fbf6360ec5e33b0

This PR is a workaround until we find a more elegant/optimal
design that also can work for gecko. The fix for now is
simply to not allow multiple layouts in parallel.

Signed-off-by: Mukilan Thiyagarajan <me@mukilan.in>
This commit is contained in:
Mukilan Thiyagarajan 2023-05-24 21:25:37 +05:30
parent 43ebf6c82c
commit 05239f879e
3 changed files with 17 additions and 19 deletions
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11
components/layout_thread_2020/lib.rs
View file

@ -517,6 +517,7 @@ impl LayoutThread {
animation_timeline_value: f64,
animations: &DocumentAnimationSet,
stylesheets_changed: bool,
use_rayon: bool,
) -> LayoutContext<'a> {
let traversal_flags = match stylesheets_changed {
true => TraversalFlags::ForCSSRuleChanges,
@ -541,7 +542,7 @@ impl LayoutThread {
font_cache_thread: Mutex::new(self.font_cache_thread.clone()),
webrender_image_cache: self.webrender_image_cache.clone(),
pending_images: Mutex::new(vec![]),
use_rayon: STYLE_THREAD_POOL.pool().is_some(),
use_rayon,
}
}
@ -989,6 +990,10 @@ impl LayoutThread {
self.stylist.flush(&guards, Some(root_element), Some(&map));
let rayon_pool = STYLE_THREAD_POOL.lock().unwrap();
let rayon_pool = rayon_pool.pool();
let rayon_pool = rayon_pool.as_ref();
// Create a layout context for use throughout the following passes.
let mut layout_context = self.build_layout_context(
guards.clone(),
@ -997,6 +1002,7 @@ impl LayoutThread {
data.animation_timeline_value,
&data.animations,
data.stylesheets_changed,
rayon_pool.is_some(),
);
let dirty_root = unsafe {
@ -1012,9 +1018,6 @@ impl LayoutThread {
RecalcStyle::pre_traverse(dirty_root, shared)
};
let rayon_pool = STYLE_THREAD_POOL.pool();
let rayon_pool = rayon_pool.as_ref();
if token.should_traverse() {
let dirty_root: ServoLayoutNode<DOMLayoutData> =
driver::traverse_dom(&traversal, token, rayon_pool).as_node();