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The following commit(s) were added to refs/heads/main by this push:
new 1dd2f5c3efc CAUSEWAY-3972: fixes _Oneshot deadlock potential
1dd2f5c3efc is described below
commit 1dd2f5c3efc26632d9050c7806779dca69a55a8b
Author: andi-huber <[email protected]>
AuthorDate: Wed Mar 4 16:40:27 2026 +0100
CAUSEWAY-3972: fixes _Oneshot deadlock potential
---
.../causeway/commons/internal/base/_Oneshot.java | 39 ++++++---------
.../commons/internal/base/_OneshotTest.java | 56 ++++++++++++++++++++++
2 files changed, 71 insertions(+), 24 deletions(-)
diff --git
a/commons/src/main/java/org/apache/causeway/commons/internal/base/_Oneshot.java
b/commons/src/main/java/org/apache/causeway/commons/internal/base/_Oneshot.java
index 3be3dda3363..698fd721cd0 100644
---
a/commons/src/main/java/org/apache/causeway/commons/internal/base/_Oneshot.java
+++
b/commons/src/main/java/org/apache/causeway/commons/internal/base/_Oneshot.java
@@ -19,35 +19,29 @@
package org.apache.causeway.commons.internal.base;
import java.io.Serializable;
+import java.util.concurrent.atomic.AtomicInteger;
/**
* <h1>- internal use only -</h1>
- * <p>
- * One-shot utility, thread-safe and serializable
- * <p>
- * <b>WARNING</b>: Do <b>NOT</b> use any of the classes provided by this
package! <br/>
+ *
+ * <p>One-shot utility, thread-safe and serializable
+ *
+ * <p><b>WARNING</b>: Do <b>NOT</b> use any of the classes provided by this
package! <br/>
* These may be changed or removed without notice!
+ *
* @since 2.0
*/
public final class _Oneshot implements Serializable {
private static final long serialVersionUID = 1L;
- private final Object $lock = new Object[0]; // serializable lock
-
- private volatile int triggerCount = 0;
+ private final AtomicInteger counter = new AtomicInteger(0); // is
serializable
/**
* Returns whether the trigger was accepted.
*/
public boolean trigger() {
- synchronized ($lock) {
- if(triggerCount==0) {
- ++ triggerCount;
- return true;
- }
- return false;
- }
+ return counter.compareAndSet(0, 1);
}
/**
@@ -56,22 +50,19 @@ public boolean trigger() {
* If the {@link Runnable} throws an {@link Exception}, this one-shot will
be exhausted regardless.
*/
public boolean trigger(final Runnable runnable) {
- synchronized ($lock) {
- if(triggerCount==0) {
- ++ triggerCount;
- runnable.run();
- }
+ // attempt to change 0 -> 1 atomically; only the thread that succeeds
runs the runnable
+ if (counter.compareAndSet(0, 1)) {
+ runnable.run();
+ return true;
+ } else
return false;
- }
}
/**
- * resets to initial condition, that is it allows one more trigger
+ * resets to initial condition, that is, it allows one more trigger
*/
public void reset() {
- synchronized ($lock) {
- triggerCount = 0;
- }
+ counter.set(0);
}
}
diff --git
a/commons/src/test/java/org/apache/causeway/commons/internal/base/_OneshotTest.java
b/commons/src/test/java/org/apache/causeway/commons/internal/base/_OneshotTest.java
new file mode 100644
index 00000000000..12ecfa93522
--- /dev/null
+++
b/commons/src/test/java/org/apache/causeway/commons/internal/base/_OneshotTest.java
@@ -0,0 +1,56 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.causeway.commons.internal.base;
+
+import java.util.concurrent.atomic.LongAdder;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.fail;
+
+import lombok.SneakyThrows;
+
+class _OneshotTest {
+
+ final _Oneshot a = new _Oneshot();
+ final LongAdder counter = new LongAdder();
+
+ @Test
+ void test() {
+ a.trigger(this::sayHelloOnce);
+ }
+
+ @SneakyThrows
+ void sayHelloOnce() {
+ if(counter.intValue()>0) {
+ fail("recursion detected");
+ }
+
+ counter.increment();
+
+ var thread = new Thread(this::doMoreWork);
+ thread.start();
+ thread.join();
+ }
+
+ void doMoreWork() {
+ a.trigger(this::sayHelloOnce);
+ }
+
+}
