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https://issues.apache.org/jira/browse/YARN-11191?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17577784#comment-17577784
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Yuan Luo commented on YARN-11191:
---------------------------------
I want to ask two question:
+ @Override
+ public List<CSQueue> getChildQueuesByTryLock() {
+ try {
+ while (!readLock.tryLock()){
+ LockSupport.parkNanos(10000);
+ }
+ return new ArrayList<CSQueue>(childQueues);
+ } finally {
+ readLock.unlock();
+ }
+ }
1.Though you use tryLock and park, so refresh queue thread switch to block
state, but this thread still hold PremmptionManager lock ,so scheduler thread
still can't allocate new container. Is it right?
2.Does this issue related to global Scheduler or just the preemption function?
Looking forward to your reply, thanks!
> Global Scheduler refreshQueue cause deadLock
> ---------------------------------------------
>
> Key: YARN-11191
> URL: https://issues.apache.org/jira/browse/YARN-11191
> Project: Hadoop YARN
> Issue Type: Bug
> Components: capacity scheduler
> Affects Versions: 2.9.0, 3.0.0, 3.1.0, 2.10.0, 3.2.0, 3.3.0
> Reporter: ben yang
> Priority: Major
> Labels: pull-request-available
> Attachments: 1.jstack, YARN-11191.001.patch
>
>
> This is a potential bug may impact all open premmption cluster.In our
> current version with preemption enabled, the capacityScheduler will call the
> refreshQueue method of the PreemptionManager when it refreshQueue. This
> process hold the preemptionManager write lock and require csqueue read
> lock.Meanwhile,ParentQueue.canAssignToThisQueue will hold csqueue readLock
> and require PreemptionManager ReadLock.
> There is a possibility of deadlock at this time.Because readlock has one rule
> on unfair policy, when a lock is already occupied by a read lock and the
> first request in the lock competition queue is a write lock request,other
> read lock requests cann‘t acquire the lock.
> So the potential deadlock is:
> {code:java}
> CapacityScheduler.refreshQueue: hold: PremmptionManager.writeLock
> require: csqueue.readLock
> CapacityScheduler.schedule: hold: csqueue.readLock
> require: PremmptionManager.readLock
> other thread(completeContainer,release Resource,etc.): require:
> csqueue.writeLock
> {code}
> The jstack logs at the time were as follows
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