tomicooler opened a new pull request, #6732:
URL: https://github.com/apache/hadoop/pull/6732
Change-Id: I4ca3998748494c1148b1ef79b33500eecae02a97
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### Description of PR
Jira: [YARN-11191](https://issues.apache.org/jira/browse/YARN-11191)
Original PR: https://github.com/apache/hadoop/pull/4726
The investigation and the fix was done by @yb12138, see the Original PR for
further details.
I fixed the leftover review comments and I slightly modified the new test
code to actually test
the `refreshQueues`. The new test fails without the fix.
### How was this patch tested?
I created a sample application for demonstration:
```java
import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.ReentrantReadWriteLock;
public class Main {
static final long start = System.currentTimeMillis();
public static void main(String[] args) {
ReentrantReadWriteLock queue = new ReentrantReadWriteLock();
ReentrantReadWriteLock preemption = new ReentrantReadWriteLock();
Thread schedulerThread = new Thread(() -> {
log("queue.readLock().lock()");
queue.readLock().lock();
try {
Thread.sleep(5 * 1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
log("preemption.readLock().lock()");
preemption.readLock().lock();
log("preemption.readLock().unlock()");
preemption.readLock().unlock();
log("queue.readLock().unlock()");
queue.readLock().unlock();
}, "SCHEDULE");
Thread completeThread = new Thread(() -> {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
log("queue.writeLock().lock()");
queue.writeLock().lock();
log("queue.writeLock().unlock()");
queue.writeLock().unlock();
}, "COMPLETE");
Thread refreshThread = new Thread(() -> {
try {
Thread.sleep(2 * 1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
log("preemption.writeLock().lock()");
preemption.writeLock().lock();
log("queue.readLock().lock()");
// OUTPUT_A
queue.readLock().lock();
// OUTPUT_B
//while (!queue.readLock().tryLock()) {
// LockSupport.parkNanos(10000);
//}
log("queue.readLock().unlock()");
queue.readLock().unlock();
log("preemption.writeLock().unlock()");
preemption.writeLock().unlock();
}, "REFRESH ");
schedulerThread.start();
completeThread.start();
refreshThread.start();
try {
schedulerThread.join();
completeThread.join();
refreshThread.join();
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}
static void log(String what) {
System.out.printf("%04d %s %s%n", System.currentTimeMillis() - start,
Thread.currentThread().getName(), what);
}
}
```
`OUTPUT_A` deadlock happens.
```
0005 SCHEDULE queue.readLock().lock()
1007 COMPLETE queue.writeLock().lock()
2006 REFRESH preemption.writeLock().lock()
2006 REFRESH queue.readLock().lock()
5042 SCHEDULE preemption.readLock().lock()
```
`OUTPUT_B` deadlock does not happen. (tryLock)
```
0003 SCHEDULE queue.readLock().lock()
1003 COMPLETE queue.writeLock().lock()
2003 REFRESH preemption.writeLock().lock()
2004 REFRESH queue.readLock().lock()
2005 REFRESH queue.readLock().unlock()
2005 REFRESH preemption.writeLock().unlock()
5026 SCHEDULE preemption.readLock().lock()
5027 SCHEDULE preemption.readLock().unlock()
5027 SCHEDULE queue.readLock().unlock()
5027 COMPLETE queue.writeLock().unlock()
```
### For code changes:
- [x] Does the title or this PR starts with the corresponding JIRA issue id
(e.g. 'YARN-11191. Your PR title ...')?
- [ ] Object storage: have the integration tests been executed and the
endpoint declared according to the connector-specific documentation?
- [ ] If adding new dependencies to the code, are these dependencies
licensed in a way that is compatible for inclusion under [ASF
2.0](http://www.apache.org/legal/resolved.html#category-a)?
- [ ] If applicable, have you updated the `LICENSE`, `LICENSE-binary`,
`NOTICE-binary` files?
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