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6803402: Race condition in AbstractQueuedSynchronizer

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Read fields in reverse initialization order

Reviewed-by: martin
This commit is contained in:
Doug Lea 2009-02-24 14:01:45 -08:00
parent ee5c2301ec
commit ca6e1aecc3
2 changed files with 8 additions and 4 deletions
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6
jdk/src/share/classes/java/util/concurrent/locks/AbstractQueuedLongSynchronizer.java
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@ -1222,8 +1222,10 @@ public abstract class AbstractQueuedLongSynchronizer
// The correctness of this depends on head being initialized // The correctness of this depends on head being initialized
// before tail and on head.next being accurate if the current // before tail and on head.next being accurate if the current
// thread is first in queue. // thread is first in queue.
Node h, s; Node t = tail; // Read fields in reverse initialization order
return (h = head) != tail && Node h = head;
Node s;
return h != t &&
((s = h.next) == null || s.thread != Thread.currentThread()); ((s = h.next) == null || s.thread != Thread.currentThread());
} }

6
jdk/src/share/classes/java/util/concurrent/locks/AbstractQueuedSynchronizer.java
View File

@ -1445,8 +1445,10 @@ public abstract class AbstractQueuedSynchronizer
// The correctness of this depends on head being initialized // The correctness of this depends on head being initialized
// before tail and on head.next being accurate if the current // before tail and on head.next being accurate if the current
// thread is first in queue. // thread is first in queue.
Node h, s; Node t = tail; // Read fields in reverse initialization order
return (h = head) != tail && Node h = head;
Node s;
return h != t &&
((s = h.next) == null || s.thread != Thread.currentThread()); ((s = h.next) == null || s.thread != Thread.currentThread());
} }