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8197812: (ref) Data race in Finalizer

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Reviewed-by: plevart, mchung
This commit is contained in:
Martin Buchholz 2018-02-15 19:35:17 -08:00
parent 0b78370b74
commit a95d50a5fc
1 changed files with 32 additions and 43 deletions

75
src/java.base/share/classes/java/lang/ref/Finalizer.java

@ -36,18 +36,18 @@ final class Finalizer extends FinalReference<Object> { /* Package-private; must
class */
private static ReferenceQueue<Object> queue = new ReferenceQueue<>();
/** Head of doubly linked list of Finalizers awaiting finalization. */
private static Finalizer unfinalized = null;
/** Lock guarding access to unfinalized list. */
private static final Object lock = new Object();
private Finalizer
next = null,
prev = null;
private Finalizer next, prev;
private boolean hasBeenFinalized() {
return (next == this);
}
private void add() {
private Finalizer(Object finalizee) {
super(finalizee, queue);
// push onto unfinalized
synchronized (lock) {
if (unfinalized != null) {
this.next = unfinalized;
@ -57,31 +57,6 @@ final class Finalizer extends FinalReference<Object> { /* Package-private; must
}
}
private void remove() {
synchronized (lock) {
if (unfinalized == this) {
if (this.next != null) {
unfinalized = this.next;
} else {
unfinalized = this.prev;
}
}
if (this.next != null) {
this.next.prev = this.prev;
}
if (this.prev != null) {
this.prev.next = this.next;
}
this.next = this; /* Indicates that this has been finalized */
this.prev = this;
}
}
private Finalizer(Object finalizee) {
super(finalizee, queue);
add();
}
static ReferenceQueue<Object> getQueue() {
return queue;
}
@ -91,11 +66,24 @@ final class Finalizer extends FinalReference<Object> { /* Package-private; must
new Finalizer(finalizee);
}
private void runFinalizer(JavaLangAccess jla) {
synchronized (this) {
if (hasBeenFinalized()) return;
remove();
private void deregisterAndRunFinalizer(JavaLangAccess jla) {
synchronized (lock) {
if (this.next == this) // already finalized
return;
// unlink from unfinalized
if (unfinalized == this)
unfinalized = this.next;
else
this.prev.next = this.next;
if (this.next != null)
this.next.prev = this.prev;
this.prev = null;
this.next = this; // mark as finalized
}
runFinalizer(jla);
}
private void runFinalizer(JavaLangAccess jla) {
try {
Object finalizee = this.get();
if (finalizee != null && !(finalizee instanceof java.lang.Enum)) {
@ -155,11 +143,8 @@ final class Finalizer extends FinalReference<Object> { /* Package-private; must
return;
final JavaLangAccess jla = SharedSecrets.getJavaLangAccess();
running = true;
for (;;) {
Finalizer f = (Finalizer)queue.poll();
if (f == null) break;
f.runFinalizer(jla);
}
for (Finalizer f; (f = (Finalizer)queue.poll()) != null; )
f.deregisterAndRunFinalizer(jla);
}
});
}
@ -179,11 +164,15 @@ final class Finalizer extends FinalReference<Object> { /* Package-private; must
final JavaLangAccess jla = SharedSecrets.getJavaLangAccess();
running = true;
for (;;) {
// "pollFirst" from unfinalized
Finalizer f;
synchronized (lock) {
f = unfinalized;
if (f == null) break;
unfinalized = f.next;
if (unfinalized != null)
unfinalized.prev = null;
f.next = f; // mark as finalized
}
f.runFinalizer(jla);
}}});
@ -214,7 +203,7 @@ final class Finalizer extends FinalReference<Object> { /* Package-private; must
for (;;) {
try {
Finalizer f = (Finalizer)queue.remove();
f.runFinalizer(jla);
f.deregisterAndRunFinalizer(jla);
} catch (InterruptedException x) {
// ignore and continue
}