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https://issues.apache.org/jira/browse/HAMA-972?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14727382#comment-14727382
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JongYoon Lim commented on HAMA-972:
-----------------------------------
+1 Thanks for the helpful link. It describes how to use the *condition wait
method*(Object.wait).
{code}
void stateDependentMethod() throws InterruptedException {
// ...
synchronized (lock) {
while (!conditionPredicate()) {
lock.wait()
}
}
// ...
}
{code}
But I concern that the *lock* is a lock which is shared between threads. So, In
my opinion, it should not be a local variable.
In the *ArrayBlockingQueue* of JDK, we can see a similar usage as below.
I can see it uses a global lock.. WDYT?
{code}
public boolean offer(E e) {
checkNotNull(e);
final ReentrantLock lock = this.lock;
lock.lock();
try {
if (count == items.length)
return false;
else {
insert(e);
return true;
}
} finally {
lock.unlock();
}
}
public void put(E e) throws InterruptedException {
checkNotNull(e);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
while (count == items.length)
notFull.await();
insert(e);
} finally {
lock.unlock();
}
}
{code}
> Synchronization on local variable
> ----------------------------------
>
> Key: HAMA-972
> URL: https://issues.apache.org/jira/browse/HAMA-972
> Project: Hama
> Issue Type: Bug
> Components: bsp core
> Reporter: JongYoon Lim
> Priority: Minor
>
> I'm not sure that the synchronization of the following code is proper.
> In the code, it uses the *call variable* as a lock. But it's a local
> variable. So whenever this function is called, the lock is changed. I think
> this is a bug... What do you think..? Is there anything that I'm missing..?
> {code}
> // Client.java
> public Writable call(Writable param, ConnectionId remoteId)
> throws InterruptedException, IOException {
> Call call = new Call(param);
> Connection connection = getConnection(remoteId, call);
> connection.sendParam(call); // send the parameter
> boolean interrupted = false;
> synchronized (call) {
> int callFailCount = 0;
> while (!call.done) {
> try {
> call.wait(1000); // wait for the result
> // prevent client hang from response error
> if (callFailCount++ == IPC_CLIENT_CONNECT_MAX_RETRIES_DEFAULT)
> break;
> } catch (InterruptedException ie) {
> interrupted = true;
> }
> }
> if (interrupted) {
> // set the interrupt flag now that we are done waiting
> Thread.currentThread().interrupt();
> }
> if (call.error != null) {
> if (call.error instanceof RemoteException) {
> call.error.fillInStackTrace();
> throw call.error;
> } else { // local exception
> // use the connection because it will reflect an ip change,
> // unlike
> // the remoteId
> throw wrapException(connection.getRemoteAddress(), call.error);
> }
> } else {
> return call.value;
> }
> }
> }
> {code}
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