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Bug 1325878: Rewrite insert_rule to avoid lock re-entrancy problems. r=xidorn
In particular, you can insertRule("@import url(\"already-loaded.css\");") and we would try to clone the stylesheet, which without this change would borrow the lock for reading. MozReview-Commit-ID: 4jdNL5rngh7 Signed-off-by: Emilio Cobos Álvarez <emilio@crisal.io>
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27ca9e0a46
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2 changed files with 96 additions and 57 deletions
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@ -135,53 +135,6 @@ impl CssRules {
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})
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}
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/// https://drafts.csswg.org/cssom/#insert-a-css-rule
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pub fn insert_rule(&mut self,
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rule: &str,
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parent_stylesheet: &Stylesheet,
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index: usize,
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nested: bool,
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loader: Option<&StylesheetLoader>)
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-> Result<CssRule, RulesMutateError> {
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// Step 1, 2
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if index > self.0.len() {
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return Err(RulesMutateError::IndexSize);
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}
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// Computes the parser state at the given index
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let state = if nested {
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None
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} else if index == 0 {
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Some(State::Start)
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} else {
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self.0.get(index - 1).map(CssRule::rule_state)
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};
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// Step 3, 4
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// XXXManishearth should we also store the namespace map?
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let (new_rule, new_state) =
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try!(CssRule::parse(&rule, parent_stylesheet, state, loader));
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// Step 5
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// Computes the maximum allowed parser state at a given index.
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let rev_state = self.0.get(index).map_or(State::Body, CssRule::rule_state);
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if new_state > rev_state {
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// We inserted a rule too early, e.g. inserting
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// a regular style rule before @namespace rules
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return Err(RulesMutateError::HierarchyRequest);
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}
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// Step 6
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if let CssRule::Namespace(..) = new_rule {
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if !self.only_ns_or_import() {
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return Err(RulesMutateError::InvalidState);
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}
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}
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self.0.insert(index, new_rule.clone());
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Ok(new_rule)
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}
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/// https://drafts.csswg.org/cssom/#remove-a-css-rule
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pub fn remove_rule(&mut self, index: usize) -> Result<(), RulesMutateError> {
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// Step 1, 2
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@ -207,6 +160,86 @@ impl CssRules {
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}
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}
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/// A trait to implement helpers for `Arc<Locked<CssRules>>`.
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pub trait CssRulesHelpers {
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/// https://drafts.csswg.org/cssom/#insert-a-css-rule
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///
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/// Written in this funky way because parsing an @import rule may cause us
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/// to clone a stylesheet from the same document due to caching in the CSS
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/// loader.
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///
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/// TODO(emilio): We could also pass the write guard down into the loader
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/// instead, but that seems overkill.
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fn insert_rule(&self,
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lock: &SharedRwLock,
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rule: &str,
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parent_stylesheet: &Stylesheet,
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index: usize,
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nested: bool,
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loader: Option<&StylesheetLoader>)
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-> Result<CssRule, RulesMutateError>;
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}
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impl CssRulesHelpers for Arc<Locked<CssRules>> {
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fn insert_rule(&self,
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lock: &SharedRwLock,
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rule: &str,
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parent_stylesheet: &Stylesheet,
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index: usize,
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nested: bool,
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loader: Option<&StylesheetLoader>)
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-> Result<CssRule, RulesMutateError> {
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let state = {
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let read_guard = lock.read();
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let rules = self.read_with(&read_guard);
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// Step 1, 2
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if index > rules.0.len() {
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return Err(RulesMutateError::IndexSize);
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}
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// Computes the parser state at the given index
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if nested {
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None
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} else if index == 0 {
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Some(State::Start)
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} else {
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rules.0.get(index - 1).map(CssRule::rule_state)
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}
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};
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// Step 3, 4
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// XXXManishearth should we also store the namespace map?
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let (new_rule, new_state) =
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try!(CssRule::parse(&rule, parent_stylesheet, state, loader));
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{
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let mut write_guard = lock.write();
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let mut rules = self.write_with(&mut write_guard);
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// Step 5
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// Computes the maximum allowed parser state at a given index.
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let rev_state = rules.0.get(index).map_or(State::Body, CssRule::rule_state);
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if new_state > rev_state {
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// We inserted a rule too early, e.g. inserting
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// a regular style rule before @namespace rules
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return Err(RulesMutateError::HierarchyRequest);
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}
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// Step 6
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if let CssRule::Namespace(..) = new_rule {
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if !rules.only_ns_or_import() {
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return Err(RulesMutateError::InvalidState);
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}
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}
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rules.0.insert(index, new_rule.clone());
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}
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Ok(new_rule)
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}
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}
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/// The structure servo uses to represent a stylesheet.
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#[derive(Debug)]
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pub struct Stylesheet {
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@ -83,8 +83,9 @@ use style::selector_parser::PseudoElementCascadeType;
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use style::sequential;
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use style::shared_lock::{SharedRwLock, SharedRwLockReadGuard, StylesheetGuards, ToCssWithGuard, Locked};
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use style::string_cache::Atom;
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use style::stylesheets::{CssRule, CssRules, CssRuleType, ImportRule, MediaRule, NamespaceRule, PageRule};
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use style::stylesheets::{Origin, Stylesheet, StyleRule};
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use style::stylesheets::{CssRule, CssRules, CssRuleType, CssRulesHelpers};
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use style::stylesheets::{ImportRule, MediaRule, NamespaceRule, Origin};
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use style::stylesheets::{PageRule, Stylesheet, StyleRule};
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use style::stylesheets::StylesheetLoader as StyleStylesheetLoader;
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use style::supports::parse_condition_or_declaration;
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use style::thread_state;
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@ -698,15 +699,20 @@ pub extern "C" fn Servo_CssRules_InsertRule(rules: ServoCssRulesBorrowed,
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};
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let loader = loader.as_ref().map(|loader| loader as &StyleStylesheetLoader);
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let rule = unsafe { rule.as_ref().unwrap().as_str_unchecked() };
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write_locked_arc(rules, |rules: &mut CssRules| {
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match rules.insert_rule(rule, sheet, index as usize, nested, loader) {
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Ok(new_rule) => {
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*unsafe { rule_type.as_mut().unwrap() } = new_rule.rule_type() as u16;
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nsresult::NS_OK
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}
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Err(err) => err.into()
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let global_style_data = &*GLOBAL_STYLE_DATA;
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match Locked::<CssRules>::as_arc(&rules).insert_rule(&global_style_data.shared_lock,
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rule,
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sheet,
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index as usize,
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nested,
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loader) {
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Ok(new_rule) => {
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*unsafe { rule_type.as_mut().unwrap() } = new_rule.rule_type() as u16;
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nsresult::NS_OK
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}
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})
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Err(err) => err.into(),
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}
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}
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#[no_mangle]
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