Github user andrewor14 commented on a diff in the pull request:
https://github.com/apache/spark/pull/10705#discussion_r53728024
--- Diff: core/src/main/scala/org/apache/spark/storage/BlockManager.scala
---
@@ -805,13 +814,12 @@ private[spark] class BlockManager(
}
}
} finally {
- // If we failed in putting the block to memory/disk, notify other
possible readers
- // that it has failed, and then remove it from the block info map.
- if (!marked) {
- // Note that the remove must happen before markFailure otherwise
another thread
- // could've inserted a new BlockInfo before we remove it.
- blockInfo.remove(blockId)
- putBlockInfo.markFailure()
+ if (!blockWasSuccessfullyStored) {
+ // Guard against the fact that MemoryStore might have already
removed the block if the
+ // put() failed and the block could not be dropped to disk.
+ if (blockInfoManager.lockForWriting(blockId, blocking =
false).isDefined) {
--- End diff --
Ohhhh, I think I got it. Let's say you try to put a block `MEMORY_ONLY` but
there is not enough space, in which case we will call
`blockManager.dropFromMemory` on that block. This call also acquires the write
lock and releases the lock in the end. However, the way this whole locking
thing works is that if I acquire the write lock twice, a single call to
`unlock` will release both locks, so if that happens we need to acquire the
write lock again here in this line.
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