servo: Merge #17710 - Revert "Auto merge of #17701 - bholley:reuse_allocations, r=emilio" (from emilio:revert-bloom-sharing); r=heycam

This reverts commit ebfc8f585834948f9b7564ffe382a6e266edf738, reversing changes made to 5585ff2c440dc27c8e98e834c9c0e9d956581b8e. Animation code can reenter and create a new TLS context from the traversal SequentialTask, so this won't work as written, and it's making test fails. Source-Repo: https://github.com/servo/servo Source-Revision: 9d74ae890b31fc45452ae60af7d89573fc52a86f --HG-- extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear extra : subtree_revision : b993fffb20fc8371a4aa42163e6712b9f1ebf33d
2017-07-13 01:26:34 -07:00 · 2017-07-13 01:26:34 -07:00 · 781f10d63c
--- a/servo/Cargo.lock
+++ b/servo/Cargo.lock
@ -1022,7 +1022,7 @@ dependencies = [
 "libc 0.2.23 (registry+https://github.com/rust-lang/crates.io-index)",
 "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 "nsstring_vendor 0.1.0",
- "parking_lot 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 "selectors 0.19.0",
 "style 0.0.1",
 "style_traits 0.0.1",
@ -1451,7 +1451,7 @@ dependencies = [
 "msg 0.0.1",
 "net_traits 0.0.1",
 "ordered-float 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parking_lot 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 "profile_traits 0.0.1",
 "range 0.0.1",
 "rayon 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
@ -1497,7 +1497,7 @@ dependencies = [
 "log 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 "msg 0.0.1",
 "net_traits 0.0.1",
- "parking_lot 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 "profile_traits 0.0.1",
 "rayon 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "script 0.0.1",
@ -2068,18 +2068,15 @@ dependencies = [

 [[package]]
 name = "owning_ref"
-version = "0.3.3"
+version = "0.2.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "stable_deref_trait 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
-]

 [[package]]
 name = "parking_lot"
-version = "0.4.4"
+version = "0.3.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "owning_ref 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "owning_ref 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)",
 "parking_lot_core 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
 "thread-id 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@ -2453,7 +2450,7 @@ dependencies = [
 "num-traits 0.1.37 (registry+https://github.com/rust-lang/crates.io-index)",
 "offscreen_gl_context 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "open 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parking_lot 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 "phf 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
 "phf_codegen 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
 "phf_shared 0.7.21 (registry+https://github.com/rust-lang/crates.io-index)",
@ -2760,7 +2757,6 @@ dependencies = [
 "heapsize 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "nodrop 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
 "serde 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "stable_deref_trait 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]

 [[package]]
@ -2912,11 +2908,6 @@ dependencies = [
 "heapsize 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]

-[[package]]
-name = "stable_deref_trait"
-version = "1.0.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-
 [[package]]
 name = "string_cache"
 version = "0.6.0"
@ -2983,8 +2974,7 @@ dependencies = [
 "num-traits 0.1.37 (registry+https://github.com/rust-lang/crates.io-index)",
 "num_cpus 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "ordered-float 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "owning_ref 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "parking_lot 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 "pdqsort 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
 "precomputed-hash 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "rayon 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
@ -3023,7 +3013,7 @@ dependencies = [
 "cssparser 0.17.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "euclid 0.15.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "html5ever 0.18.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "parking_lot 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 "rayon 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)",
 "rustc-serialize 0.3.24 (registry+https://github.com/rust-lang/crates.io-index)",
 "selectors 0.19.0",
@ -3756,8 +3746,8 @@ dependencies = [
 "checksum ordered-float 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "da12c96037889ae0be29dd2bdd260e5a62a7df24e6466d5a15bb8131c1c200a8"
 "checksum osmesa-src 12.0.1 (git+https://github.com/servo/osmesa-src)" = "<none>"
 "checksum osmesa-sys 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "88cfece6e95d2e717e0872a7f53a8684712ad13822a7979bc760b9c77ec0013b"
-"checksum owning_ref 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "cdf84f41639e037b484f93433aa3897863b561ed65c6e59c7073d7c561710f37"
-"checksum parking_lot 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)" = "37f364e2ce5efa24c7d0b6646d5bb61145551a0112f107ffd7499f1a3e322fbd"
+"checksum owning_ref 0.2.4 (registry+https://github.com/rust-lang/crates.io-index)" = "9d52571ddcb42e9c900c901a18d8d67e393df723fcd51dd59c5b1a85d0acb6cc"
+"checksum parking_lot 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)" = "fa12d706797d42551663426a45e2db2e0364bd1dbf6aeada87e89c5f981f43e9"
 "checksum parking_lot_core 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "0ad2c4d148942b3560034785bf19df586ebba53351e8c78f84984147d5795eef"
 "checksum parse-hosts 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9aebf4a4f84ce5d940a30a919c93325a66ab4ddb646f5f0a3d77483eb99595a6"
 "checksum pdqsort 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "ceca1642c89148ca05611cc775a0c383abef355fc4907c4e95f49f7b09d6287c"
@ -3815,7 +3805,6 @@ dependencies = [
 "checksum skeptic 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "dd7d8dc1315094150052d0ab767840376335a98ac66ef313ff911cdf439a5b69"
 "checksum slab 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "17b4fcaed89ab08ef143da37bc52adbcc04d4a69014f4c1208d6b51f0c47bc23"
 "checksum smallvec 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "2e40af10aafe98b4d8294ae8388d8a5cd0707c65d364872efe72d063ec44bee0"
-"checksum stable_deref_trait 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "15132e0e364248108c5e2c02e3ab539be8d6f5d52a01ca9bbf27ed657316f02b"
 "checksum string_cache 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "23429a3aca80e7cc7f0060853a97fbba9a90e30ef36b29d13e22559cd7f3dc54"
 "checksum string_cache_codegen 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "479cde50c3539481f33906a387f2bd17c8e87cb848c35b6021d41fb81ff9b4d7"
 "checksum string_cache_shared 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b1884d1bc09741d466d9b14e6d37ac89d6909cbcac41dd9ae982d4d063bbedfc"
--- a/servo/components/layout/Cargo.toml
+++ b/servo/components/layout/Cargo.toml
@ -26,7 +26,7 @@ log = "0.3.5"
 msg = {path = "../msg"}
 net_traits = {path = "../net_traits"}
 ordered-float = "0.4"
-parking_lot = "0.4"
+parking_lot = "0.3.3"
 profile_traits = {path = "../profile_traits"}
 range = {path = "../range"}
 rayon = "0.8"
--- a/servo/components/layout_thread/Cargo.toml
+++ b/servo/components/layout_thread/Cargo.toml
@ -23,7 +23,7 @@ lazy_static = "0.2"
 log = "0.3.5"
 msg = {path = "../msg"}
 net_traits = {path = "../net_traits"}
-parking_lot = {version = "0.4", features = ["nightly"]}
+parking_lot = {version = "0.3.3", features = ["nightly"]}
 profile_traits = {path = "../profile_traits"}
 rayon = "0.8"
 script = {path = "../script"}
--- a/servo/components/script/Cargo.toml
+++ b/servo/components/script/Cargo.toml
@ -65,7 +65,7 @@ net_traits = {path = "../net_traits"}
 num-traits = "0.1.32"
 offscreen_gl_context = { version = "0.11", features = ["serde"] }
 open = "1.1.1"
-parking_lot = "0.4"
+parking_lot = "0.3"
 phf = "0.7.18"
 profile_traits = {path = "../profile_traits"}
 range = {path = "../range"}
--- a/servo/components/servo_arc/Cargo.toml
+++ b/servo/components/servo_arc/Cargo.toml
@ -14,6 +14,5 @@ servo = ["serde", "heapsize"]

 [dependencies]
 heapsize = {version = "0.4.0", optional = true}
-nodrop = {version = "0.1.8"}
 serde = {version = "1.0", optional = true}
-stable_deref_trait = "1.0.0"
+nodrop = {version = "0.1.8"}
--- a/servo/components/servo_arc/lib.rs
+++ b/servo/components/servo_arc/lib.rs
@ -22,16 +22,14 @@
 // duplicate those here.
 #![allow(missing_docs)]

-extern crate nodrop;
 #[cfg(feature = "servo")] extern crate serde;
-extern crate stable_deref_trait;
+extern crate nodrop;

 #[cfg(feature = "servo")]
 use heapsize::HeapSizeOf;
 use nodrop::NoDrop;
 #[cfg(feature = "servo")]
 use serde::{Deserialize, Serialize};
-use stable_deref_trait::{CloneStableDeref, StableDeref};
 use std::{isize, usize};
 use std::borrow;
 use std::cmp::Ordering;
@ -434,9 +432,6 @@ impl<T: ?Sized> AsRef<T> for Arc<T> {
    }
 }

-unsafe impl<T: ?Sized> StableDeref for Arc<T> {}
-unsafe impl<T: ?Sized> CloneStableDeref for Arc<T> {}
-
 // This is what the HeapSize crate does for regular arc, but is questionably
 // sound. See https://github.com/servo/heapsize/issues/37
 #[cfg(feature = "servo")]
--- a/servo/components/style/Cargo.toml
+++ b/servo/components/style/Cargo.toml
@ -54,8 +54,7 @@ num_cpus = {version = "1.1.0", optional = true}
 num-integer = "0.1.32"
 num-traits = "0.1.32"
 ordered-float = "0.4"
-owning_ref = "0.3.3"
-parking_lot = "0.4"
+parking_lot = "0.3.3"
 pdqsort = "0.1.0"
 precomputed-hash = "0.1"
 rayon = "0.8"
--- a/servo/components/style/bloom.rs
+++ b/servo/components/style/bloom.rs
@ -7,18 +7,9 @@

 #![deny(missing_docs)]

-use atomic_refcell::{AtomicRefMut, AtomicRefCell};
 use dom::{SendElement, TElement};
-use owning_ref::OwningHandle;
 use selectors::bloom::BloomFilter;
 use smallvec::SmallVec;
-use stylearc::Arc;
-
-/// Bloom filters are large allocations, so we store them in thread-local storage
-/// such that they can be reused across style traversals. StyleBloom is responsible
-/// for ensuring that the bloom filter is zeroed when it is dropped.
-thread_local!(static BLOOM_KEY: Arc<AtomicRefCell<BloomFilter>> =
-              Arc::new(AtomicRefCell::new(BloomFilter::new())));

 /// A struct that allows us to fast-reject deep descendant selectors avoiding
 /// selector-matching.
@ -52,11 +43,8 @@ thread_local!(static BLOOM_KEY: Arc<AtomicRefCell<BloomFilter>> =
 ///    immutable during a restyle.
 ///
 pub struct StyleBloom<E: TElement> {
-    /// A handle to the bloom filter from the thread upon which this StyleBloom
-    /// was created. We use AtomicRefCell so that this is all |Send|, which allows
-    /// StyleBloom to live in ThreadLocalStyleContext, which is dropped from the
-    /// parent thread.
-    filter: OwningHandle<Arc<AtomicRefCell<BloomFilter>>, AtomicRefMut<'static, BloomFilter>>,
+    /// The bloom filter per se.
+    filter: Box<BloomFilter>,

    /// The stack of elements that this bloom filter contains, along with the
    /// number of hashes pushed for each element.
@ -113,23 +101,11 @@ fn each_relevant_element_hash<E, F>(element: E, mut f: F)
    });
 }

-impl<E: TElement> Drop for StyleBloom<E> {
-    fn drop(&mut self) {
-        // Leave the reusable bloom filter in a zeroed state.
-        self.clear();
-    }
-}
-
 impl<E: TElement> StyleBloom<E> {
-    /// Create an empty `StyleBloom`. Because StyleBloom acquires the thread-
-    /// local filter buffer, creating multiple live StyleBloom instances at
-    /// the same time on the same thread will panic.
+    /// Create an empty `StyleBloom`.
    pub fn new() -> Self {
-        let bloom_arc = BLOOM_KEY.with(|b| b.clone());
-        let filter = OwningHandle::new_with_fn(bloom_arc, |x| unsafe { x.as_ref() }.unwrap().borrow_mut());
-        debug_assert!(filter.is_zeroed(), "Forgot to zero the bloom filter last time");
        StyleBloom {
-            filter: filter,
+            filter: Box::new(BloomFilter::new()),
            elements: Default::default(),
            pushed_hashes: Default::default(),
        }
--- a/servo/components/style/lib.rs
+++ b/servo/components/style/lib.rs
@ -67,7 +67,6 @@ pub extern crate nsstring_vendor as nsstring;
 extern crate num_integer;
 extern crate num_traits;
 extern crate ordered_float;
-extern crate owning_ref;
 extern crate parking_lot;
 extern crate pdqsort;
 #[cfg(feature = "gecko")] extern crate precomputed_hash;
--- a/servo/components/style/sharing/mod.rs
+++ b/servo/components/style/sharing/mod.rs
@ -66,7 +66,6 @@

 use Atom;
 use applicable_declarations::ApplicableDeclarationBlock;
-use atomic_refcell::{AtomicRefCell, AtomicRefMut};
 use bit_vec::BitVec;
 use bloom::StyleBloom;
 use cache::{LRUCache, LRUCacheMutIterator};
@ -74,15 +73,12 @@ use context::{SelectorFlagsMap, SharedStyleContext, StyleContext};
 use data::{ElementData, ElementStyles};
 use dom::{TElement, SendElement};
 use matching::{ChildCascadeRequirement, MatchMethods};
-use owning_ref::OwningHandle;
 use properties::ComputedValues;
 use selector_parser::RestyleDamage;
 use selectors::matching::{ElementSelectorFlags, VisitedHandlingMode};
 use smallvec::SmallVec;
-use std::marker::PhantomData;
 use std::mem;
 use std::ops::Deref;
-use stylearc::Arc;
 use stylist::Stylist;

 mod checks;
@ -97,8 +93,7 @@ mod checks;
 /// improvements (e.g. 3x fewer styles having to be resolved than at size 8) and
 /// slight performance improvements.  Sizes larger than 32 haven't really been
 /// tested.
-pub const SHARING_CACHE_SIZE: usize = 31;
-const SHARING_CACHE_BACKING_STORE_SIZE: usize = SHARING_CACHE_SIZE + 1;
+pub const STYLE_SHARING_CANDIDATE_CACHE_SIZE: usize = 31;

 /// Controls whether the style sharing cache is used.
 #[derive(Clone, Copy, PartialEq)]
@ -216,21 +211,14 @@ impl ValidationData {
 /// Note that this information is stored in TLS and cleared after the traversal,
 /// and once here, the style information of the element is immutable, so it's
 /// safe to access.
-///
-/// Important: If you change the members/layout here, You need to do the same for
-/// FakeCandidate below.
 #[derive(Debug)]
 pub struct StyleSharingCandidate<E: TElement> {
-    /// The element.
-    element: E,
+    /// The element. We use SendElement here so that the cache may live in
+    /// ScopedTLS.
+    element: SendElement<E>,
    validation_data: ValidationData,
 }

-struct FakeCandidate {
-    _element: usize,
-    _validation_data: ValidationData,
-}
-
 impl<E: TElement> Deref for StyleSharingCandidate<E> {
    type Target = E;

@ -243,12 +231,12 @@ impl<E: TElement> Deref for StyleSharingCandidate<E> {
 impl<E: TElement> StyleSharingCandidate<E> {
    /// Get the classlist of this candidate.
    fn class_list(&mut self) -> &[Atom] {
-        self.validation_data.class_list(self.element)
+        self.validation_data.class_list(*self.element)
    }

    /// Get the pres hints of this candidate.
    fn pres_hints(&mut self) -> &[ApplicableDeclarationBlock] {
-        self.validation_data.pres_hints(self.element)
+        self.validation_data.pres_hints(*self.element)
    }

    /// Compute the bit vector of revalidation selector match results
@ -259,7 +247,7 @@ impl<E: TElement> StyleSharingCandidate<E> {
        bloom: &StyleBloom<E>,
    ) -> &BitVec {
        self.validation_data.revalidation_match_results(
-            self.element,
+            *self.element,
            stylist,
            bloom,
            /* bloom_known_valid = */ false,
@ -469,81 +457,35 @@ pub enum StyleSharingResult {
    StyleWasShared(usize, ChildCascadeRequirement),
 }

-/// Style sharing caches are are large allocations, so we store them in thread-local
-/// storage such that they can be reused across style traversals. Ideally, we'd just
-/// stack-allocate these buffers with uninitialized memory, but right now rustc can't
-/// avoid memmoving the entire cache during setup, which gets very expensive. See
-/// issues like [1] and [2].
-///
-/// Given that the cache stores entries of type TElement, we transmute to usize
-/// before storing in TLS. This is safe as long as we make sure to empty the cache
-/// before we let it go.
-///
-/// [1] https://github.com/rust-lang/rust/issues/42763
-/// [2] https://github.com/rust-lang/rust/issues/13707
-type SharingCacheBase<Candidate> = LRUCache<[Candidate; SHARING_CACHE_BACKING_STORE_SIZE]>;
-type SharingCache<E> = SharingCacheBase<StyleSharingCandidate<E>>;
-type TypelessSharingCache = SharingCacheBase<FakeCandidate>;
-type StoredSharingCache = Arc<AtomicRefCell<TypelessSharingCache>>;
-
-thread_local!(static SHARING_CACHE_KEY: StoredSharingCache =
-              Arc::new(AtomicRefCell::new(LRUCache::new())));
-
 /// An LRU cache of the last few nodes seen, so that we can aggressively try to
 /// reuse their styles.
 ///
 /// Note that this cache is flushed every time we steal work from the queue, so
 /// storing nodes here temporarily is safe.
 pub struct StyleSharingCandidateCache<E: TElement> {
-    /// The LRU cache, with the type cast away to allow persisting the allocation.
-    cache_typeless: OwningHandle<StoredSharingCache, AtomicRefMut<'static, TypelessSharingCache>>,
-    /// Bind this structure to the lifetime of E, since that's what we effectively store.
-    marker: PhantomData<SendElement<E>>,
+    cache: LRUCache<[StyleSharingCandidate<E>; STYLE_SHARING_CANDIDATE_CACHE_SIZE + 1]>,
    /// The DOM depth we're currently at.  This is used as an optimization to
    /// clear the cache when we change depths, since we know at that point
    /// nothing in the cache will match.
    dom_depth: usize,
 }

-impl<E: TElement> Drop for StyleSharingCandidateCache<E> {
-    fn drop(&mut self) {
-        self.clear();
-    }
-}
-
 impl<E: TElement> StyleSharingCandidateCache<E> {
-    fn cache(&self) -> &SharingCache<E> {
-        let base: &TypelessSharingCache = &*self.cache_typeless;
-        unsafe { mem::transmute(base) }
-    }
-
-    fn cache_mut(&mut self) -> &mut SharingCache<E> {
-        let base: &mut TypelessSharingCache = &mut *self.cache_typeless;
-        unsafe { mem::transmute(base) }
-    }
-
    /// Create a new style sharing candidate cache.
    pub fn new() -> Self {
-        assert_eq!(mem::size_of::<SharingCache<E>>(), mem::size_of::<TypelessSharingCache>());
-        assert_eq!(mem::align_of::<SharingCache<E>>(), mem::align_of::<TypelessSharingCache>());
-        let cache_arc = SHARING_CACHE_KEY.with(|c| c.clone());
-        let cache = OwningHandle::new_with_fn(cache_arc, |x| unsafe { x.as_ref() }.unwrap().borrow_mut());
-        debug_assert_eq!(cache.num_entries(), 0);
-
        StyleSharingCandidateCache {
-            cache_typeless: cache,
-            marker: PhantomData,
+            cache: LRUCache::new(),
            dom_depth: 0,
        }
    }

    /// Returns the number of entries in the cache.
    pub fn num_entries(&self) -> usize {
-        self.cache().num_entries()
+        self.cache.num_entries()
    }

    fn iter_mut(&mut self) -> LRUCacheMutIterator<StyleSharingCandidate<E>> {
-        self.cache_mut().iter_mut()
+        self.cache.iter_mut()
    }

    /// Tries to insert an element in the style sharing cache.
@ -588,20 +530,20 @@ impl<E: TElement> StyleSharingCandidateCache<E> {
            self.clear();
            self.dom_depth = dom_depth;
        }
-        self.cache_mut().insert(StyleSharingCandidate {
-            element: *element,
+        self.cache.insert(StyleSharingCandidate {
+            element: unsafe { SendElement::new(*element) },
            validation_data: validation_data,
        });
    }

    /// Touch a given index in the style sharing candidate cache.
    pub fn touch(&mut self, index: usize) {
-        self.cache_mut().touch(index);
+        self.cache.touch(index);
    }

    /// Clear the style sharing candidate cache.
    pub fn clear(&mut self) {
-        self.cache_mut().evict_all()
+        self.cache.evict_all()
    }

    /// Attempts to share a style with another node.
@ -668,7 +610,7 @@ impl<E: TElement> StyleSharingCandidateCache<E> {
        }

        debug!("{:?} Cannot share style: {} cache entries", target.element,
-               self.cache().num_entries());
+               self.cache.num_entries());

        StyleSharingResult::CannotShare
    }
--- a/servo/ports/geckolib/Cargo.toml
+++ b/servo/ports/geckolib/Cargo.toml
@ -21,7 +21,7 @@ env_logger = {version = "0.4", default-features = false} # disable `regex` to re
 libc = "0.2"
 log = {version = "0.3.5", features = ["release_max_level_info"]}
 nsstring_vendor = {path = "../../components/style/gecko_bindings/nsstring_vendor"}
-parking_lot = "0.4"
+parking_lot = "0.3"
 selectors = {path = "../../components/selectors"}
 style = {path = "../../components/style", features = ["gecko"]}
 style_traits = {path = "../../components/style_traits"}
--- a/servo/tests/unit/style/Cargo.toml
+++ b/servo/tests/unit/style/Cargo.toml
@ -18,7 +18,7 @@ app_units = "0.5"
 cssparser = "0.17.0"
 euclid = "0.15"
 html5ever = "0.18"
-parking_lot = "0.4"
+parking_lot = "0.3"
 rayon = "0.8"
 rustc-serialize = "0.3"
 selectors = {path = "../../../components/selectors"}