diff options
Diffstat (limited to 'components/style/rule_tree/mod.rs')
| -rw-r--r-- | components/style/rule_tree/mod.rs | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/components/style/rule_tree/mod.rs b/components/style/rule_tree/mod.rs index abbfe7f3efb..07b14370f40 100644 --- a/components/style/rule_tree/mod.rs +++ b/components/style/rule_tree/mod.rs @@ -122,6 +122,10 @@ impl StyleSource { /// The root node doesn't have a null pointer in the free list, but this value. const FREE_LIST_SENTINEL: *mut RuleNode = 0x01 as *mut RuleNode; +/// A second sentinel value for the free list, indicating that it's locked (i.e. +/// another thread is currently adding an entry). We spin if we find this value. +const FREE_LIST_LOCKED: *mut RuleNode = 0x02 as *mut RuleNode; + impl RuleTree { /// Construct a new rule tree. pub fn new() -> Self { @@ -1395,7 +1399,7 @@ impl Drop for StrongRuleNode { return; } - // Ensure we "lock" the free list head swapping it with a null pointer. + // Ensure we "lock" the free list head swapping it with FREE_LIST_LOCKED. // // Note that we use Acquire/Release semantics for the free list // synchronization, in order to guarantee that the next_free @@ -1404,11 +1408,11 @@ impl Drop for StrongRuleNode { let mut old_head = free_list.load(Ordering::Relaxed); loop { match free_list.compare_exchange_weak(old_head, - ptr::null_mut(), + FREE_LIST_LOCKED, Ordering::Acquire, Ordering::Relaxed) { Ok(..) => { - if !old_head.is_null() { + if old_head != FREE_LIST_LOCKED { break; } }, |