Github user zsxwing commented on a diff in the pull request:
https://github.com/apache/spark/pull/1542#discussion_r15392537
--- Diff: core/src/main/scala/org/apache/spark/MapOutputTracker.scala ---
@@ -162,9 +164,9 @@ private[spark] abstract class MapOutputTracker(conf:
SparkConf) extends Logging
logInfo("Got the output locations")
mapStatuses.put(shuffleId, fetchedStatuses)
} finally {
- fetching.synchronized {
- fetching -= shuffleId
- fetching.notifyAll()
+ monitor.synchronized {
+ fetching.remove(shuffleId)
+ monitor.notifyAll()
--- End diff --
The read/write operation of `fetching` should use the same monitor
according to the java memory model.
> In addition, using the monitor of an object from outside to synchronized
makes it hard to analyse the codes because the monitor of this object may be
used (or used in the future) in other place and the developer may not notice
somebody has already used it here.
Also this problem looks hard to solve.
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