Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/incubator-flink/pull/126#discussion_r18402745
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flink-runtime/src/main/java/org/apache/flink/runtime/execution/librarycache/BlobLibraryCacheManager.java
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I think the logic with the lock map is dangerous, and most likely even not
more efficient than a simple lock.
Previous versions of the LibraryCacheManager has errors that the locks were
not always removed, leading to endless spins. Manual spinning is not required
any more, the JVM does adaptive spinning that automatically degrades to queued
waiting, which is better than anything we could hope to implement manually.
Since we do not expect congestion on this class, even the most simple
global lock might do (and would be lightweight for the JVM).
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