Skip to content

Fix race condition in P1.memo() #106

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
mperry merged 1 commit into from
Feb 11, 2015
Merged

Fix race condition in P1.memo() #106

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 5 additions & 2 deletions core/src/main/java/fj/P1.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -223,9 +223,12 @@ public A _1() {
A a = v != null ? v.get() : null;
if (a == null)
synchronized (latch) {
if (v == null || v.get() == null)
if (v == null || v.get() == null) {
a = self._1();
v = new SoftReference<A>(a);
v = new SoftReference<A>(a);
} else {
a = v.get();
}
}
return a;
}
Expand Down
31 changes: 31 additions & 0 deletions core/src/test/java/fj/P1Test.java
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,31 @@
package fj;

import org.junit.Test;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

public final class P1Test {

@Test
public void bug105() throws Exception {
final P1<String> p1 = P.p("Foo").memo();
final AtomicInteger nullCounter = new AtomicInteger();
ExecutorService executorService = Executors.newCachedThreadPool();

for (int i = 0; i < 10000; i++) {
executorService.submit(() -> {
if (p1._1() == null) {
nullCounter.incrementAndGet();
}
});
}

executorService.shutdown();
executorService.awaitTermination(10, TimeUnit.DAYS);

org.junit.Assert.assertEquals("Race condition in P1.memo()", 0, nullCounter.get());
}
}