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rule tree: more descriptive field names

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This commit is contained in:
Simon Sapin 2016-11-05 14:17:48 +01:00
parent 2dd2c9cedd
commit 1a18161006
1 changed files with 83 additions and 93 deletions
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176
components/style/rule_tree/mod.rs
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@ -120,6 +120,7 @@ impl RuleTree {
current
}
/// This can only be called when no other threads is accessing this tree.
pub unsafe fn gc(&self) {
self.root.gc();
}
@ -140,10 +141,10 @@ struct RuleNode {
/// meaningless in the root node.
importance: Importance,
children: RuleChildrenList,
refcount: AtomicUsize,
next: AtomicPtr<RuleNode>,
prev: AtomicPtr<RuleNode>,
first_child: AtomicPtr<RuleNode>,
next_sibling: AtomicPtr<RuleNode>,
prev_sibling: AtomicPtr<RuleNode>,
/// The next item in the rule tree free list, that starts on the root node.
next_free: AtomicPtr<RuleNode>,
@ -163,10 +164,10 @@ impl RuleNode {
parent: Some(parent),
source: Some(source),
importance: importance,
children: RuleChildrenList::new(),
refcount: AtomicUsize::new(1),
next: AtomicPtr::new(ptr::null_mut()),
prev: AtomicPtr::new(ptr::null_mut()),
first_child: AtomicPtr::new(ptr::null_mut()),
next_sibling: AtomicPtr::new(ptr::null_mut()),
prev_sibling: AtomicPtr::new(ptr::null_mut()),
next_free: AtomicPtr::new(ptr::null_mut()),
}
}
@ -177,10 +178,10 @@ impl RuleNode {
parent: None,
source: None,
importance: Importance::Normal,
children: RuleChildrenList::new(),
refcount: AtomicUsize::new(1),
next: AtomicPtr::new(ptr::null_mut()),
prev: AtomicPtr::new(ptr::null_mut()),
first_child: AtomicPtr::new(ptr::null_mut()),
next_sibling: AtomicPtr::new(ptr::null_mut()),
prev_sibling: AtomicPtr::new(ptr::null_mut()),
next_free: AtomicPtr::new(FREE_LIST_SENTINEL),
}
}
@ -199,21 +200,21 @@ impl RuleNode {
unsafe fn remove_from_child_list(&self) {
debug!("Remove from child list: {:?}, parent: {:?}",
self as *const RuleNode, self.parent.as_ref().map(|p| p.ptr()));
let previous = self.prev.swap(ptr::null_mut(), Ordering::SeqCst);
let next = self.next.swap(ptr::null_mut(), Ordering::SeqCst);
let prev_sibling = self.prev_sibling.swap(ptr::null_mut(), Ordering::SeqCst);
let next_sibling = self.next_sibling.swap(ptr::null_mut(), Ordering::SeqCst);
if previous != ptr::null_mut() {
let really_previous = WeakRuleNode { ptr: previous };
if prev_sibling != ptr::null_mut() {
let really_previous = WeakRuleNode { ptr: prev_sibling };
really_previous.upgrade()
.get().next.store(next, Ordering::SeqCst);
.get().next_sibling.store(next_sibling, Ordering::SeqCst);
} else {
self.parent.as_ref().unwrap()
.get().children.head.store(ptr::null_mut(), Ordering::SeqCst);
.get().first_child.store(ptr::null_mut(), Ordering::SeqCst);
}
if next != ptr::null_mut() {
let really_next = WeakRuleNode { ptr: next };
really_next.upgrade().get().prev.store(previous, Ordering::SeqCst);
if next_sibling != ptr::null_mut() {
let really_next = WeakRuleNode { ptr: next_sibling };
really_next.upgrade().get().prev_sibling.store(prev_sibling, Ordering::SeqCst);
}
}
@ -245,10 +246,22 @@ impl RuleNode {
}
let _ = write!(writer, "\n");
for child in self.children.iter() {
for child in self.iter_children() {
child.get().dump(writer, indent + INDENT_INCREMENT);
}
}
fn iter_children(&self) -> RuleChildrenListIter {
// FIXME(emilio): Fiddle with memory orderings.
let first_child = self.first_child.load(Ordering::SeqCst);
RuleChildrenListIter {
current: if first_child.is_null() {
None
} else {
Some(WeakRuleNode { ptr: first_child })
}
}
}
}
#[derive(Clone)]
@ -286,10 +299,10 @@ impl StrongRuleNode {
}
}
fn next(&self) -> Option<WeakRuleNode> {
fn next_sibling(&self) -> Option<WeakRuleNode> {
// FIXME(emilio): Investigate what ordering can we achieve without
// messing things up.
let ptr = self.get().next.load(Ordering::SeqCst);
let ptr = self.get().next_sibling.load(Ordering::SeqCst);
if ptr.is_null() {
None
} else {
@ -308,7 +321,7 @@ impl StrongRuleNode {
source: StyleSource,
importance: Importance) -> StrongRuleNode {
let mut last = None;
for child in self.get().children.iter() {
for child in self.get().iter_children() {
if child .get().importance == importance &&
child.get().source.as_ref().unwrap().ptr_equals(&source) {
return child;
@ -316,25 +329,25 @@ impl StrongRuleNode {
last = Some(child);
}
let node = Box::new(RuleNode::new(root,
self.clone(),
source.clone(),
importance));
let new_ptr = &*node as *const _ as *mut RuleNode;
let mut node = Box::new(RuleNode::new(root,
self.clone(),
source.clone(),
importance));
let new_ptr: *mut RuleNode = &mut *node;
loop {
let strong;
{
let next_ptr = match last {
Some(ref l) => &l.get().next,
None => &self.get().children.head,
let next_sibling_ptr = match last {
Some(ref l) => &l.get().next_sibling,
None => &self.get().first_child,
};
let existing =
next_ptr.compare_and_swap(ptr::null_mut(),
new_ptr,
Ordering::SeqCst);
next_sibling_ptr.compare_and_swap(ptr::null_mut(),
new_ptr,
Ordering::SeqCst);
if existing == ptr::null_mut() {
// Now we know we're in the correct position in the child list,
@ -342,21 +355,22 @@ impl StrongRuleNode {
// accessed again in a single-threaded manner when we're
// sweeping possibly dead nodes.
if let Some(ref l) = last {
node.prev.store(l.ptr(), Ordering::Relaxed);
node.prev_sibling.store(l.ptr(), Ordering::Relaxed);
}
return StrongRuleNode::new(node);
}
// Existing is not null: some thread insert a child node since we accessed `last`.
strong = WeakRuleNode { ptr: existing }.upgrade();
if strong.get().source.as_ref().unwrap().ptr_equals(&source) {
// Some thread that was racing with as inserted the same rule
// node than us, so give up and just use that.
// That node happens to be for the same style source, use that.
return strong;
}
}
// Try again inserting after the new last child.
last = Some(strong);
}
}
@ -479,40 +493,42 @@ impl Drop for StrongRuleNode {
node.refcount.fetch_sub(1, Ordering::SeqCst) == 1
};
if should_drop {
debug_assert_eq!(node.children.head.load(Ordering::SeqCst),
ptr::null_mut());
if node.parent.is_none() {
debug!("Dropping root node!");
// NOTE: Calling this is fine, because the rule tree root
// destructor needs to happen from the layout thread, where the
// stylist, and hence, the rule tree, is held.
unsafe { self.gc() };
let _ = unsafe { Box::from_raw(self.ptr()) };
return;
}
if !should_drop {
return
}
// The node is already in the free list, so do nothing.
if node.next_free.load(Ordering::SeqCst) != ptr::null_mut() {
return;
}
debug_assert_eq!(node.first_child.load(Ordering::SeqCst),
ptr::null_mut());
if node.parent.is_none() {
debug!("Dropping root node!");
// NOTE: Calling this is fine, because the rule tree root
// destructor needs to happen from the layout thread, where the
// stylist, and hence, the rule tree, is held.
unsafe { self.gc() };
let _ = unsafe { Box::from_raw(self.ptr()) };
return;
}
let free_list =
&unsafe { &*node.root.as_ref().unwrap().ptr() }.next_free;
loop {
let next_free = free_list.load(Ordering::SeqCst);
debug_assert!(!next_free.is_null());
// The node is already in the free list, so do nothing.
if node.next_free.load(Ordering::SeqCst) != ptr::null_mut() {
return;
}
node.next_free.store(next_free, Ordering::SeqCst);
let free_list =
&unsafe { &*node.root.as_ref().unwrap().ptr() }.next_free;
loop {
let next_free = free_list.load(Ordering::SeqCst);
debug_assert!(!next_free.is_null());
let existing =
free_list.compare_and_swap(next_free,
self.ptr(),
Ordering::SeqCst);
if existing == next_free {
// Successfully inserted, yay! Otherwise try again.
break;
}
node.next_free.store(next_free, Ordering::SeqCst);
let existing =
free_list.compare_and_swap(next_free,
self.ptr(),
Ordering::SeqCst);
if existing == next_free {
// Successfully inserted, yay! Otherwise try again.
break;
}
}
}
@ -542,32 +558,6 @@ impl WeakRuleNode {
}
}
struct RuleChildrenList {
head: AtomicPtr<RuleNode>,
}
impl RuleChildrenList {
fn new() -> Self {
RuleChildrenList {
head: AtomicPtr::new(ptr::null_mut())
}
}
fn iter(&self) -> RuleChildrenListIter {
// FIXME(emilio): Fiddle with memory orderings.
let head = self.head.load(Ordering::SeqCst);
RuleChildrenListIter {
current: if head.is_null() {
None
} else {
Some(WeakRuleNode {
ptr: head,
})
},
}
}
}
struct RuleChildrenListIter {
current: Option<WeakRuleNode>,
}
@ -578,7 +568,7 @@ impl Iterator for RuleChildrenListIter {
fn next(&mut self) -> Option<Self::Item> {
self.current.take().map(|current| {
let current = current.upgrade();
self.current = current.next();
self.current = current.next_sibling();
current
})
}