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[SPARK-26265][Core][Followup] Put freePage into a finally block #23294

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[SPARK-26265][Core][Followup] Put freePage into a finally block #23294

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57 changes: 30 additions & 27 deletions core/src/main/java/org/apache/spark/unsafe/map/BytesToBytesMap.java
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Original file line number Diff line number Diff line change
Expand Up @@ -262,36 +262,39 @@ private void advanceToNextPage() {
// reference to the page to free and free it after releasing the lock of `MapIterator`.
MemoryBlock pageToFree = null;

synchronized (this) {
int nextIdx = dataPages.indexOf(currentPage) + 1;
if (destructive && currentPage != null) {
dataPages.remove(currentPage);
pageToFree = currentPage;
nextIdx --;
}
if (dataPages.size() > nextIdx) {
currentPage = dataPages.get(nextIdx);
pageBaseObject = currentPage.getBaseObject();
offsetInPage = currentPage.getBaseOffset();
recordsInPage = UnsafeAlignedOffset.getSize(pageBaseObject, offsetInPage);
offsetInPage += UnsafeAlignedOffset.getUaoSize();
} else {
currentPage = null;
if (reader != null) {
handleFailedDelete();
try {
synchronized (this) {
int nextIdx = dataPages.indexOf(currentPage) + 1;
if (destructive && currentPage != null) {
dataPages.remove(currentPage);
pageToFree = currentPage;
nextIdx--;
}
try {
Closeables.close(reader, /* swallowIOException = */ false);
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shall we close the reader outside of the synchronized block? Then we don't need to extra try catch.

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In the second try, it accesses spillWriters:

reader = spillWriters.getFirst().getReader(serializerManager)

The synchronized spill will change spillWriters. Seems to be unsafe if we close the reader and update reader like above outside synchronized?

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how about

UnsafeSorterSpillReader readerToClose = null;
synchronized (this) {
  ...
  readerToClose  = reader;
  reader = spillWriters.getFirst().getReader(serializerManager);
  ...
}
try {
  Closeables.close(readerToClose, /* swallowIOException = */ false);
} catch ...

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I'm not sure of the semantics here, but because the close block is changing several fields at once, it seems more conservative to leave them as they are within the synchronized block. At least, that is a separate issue.

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@cloud-fan What do you think?

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I think it's okay to go ahead as is

reader = spillWriters.getFirst().getReader(serializerManager);
recordsInPage = -1;
} catch (IOException e) {
// Scala iterator does not handle exception
Platform.throwException(e);
if (dataPages.size() > nextIdx) {
currentPage = dataPages.get(nextIdx);
pageBaseObject = currentPage.getBaseObject();
offsetInPage = currentPage.getBaseOffset();
recordsInPage = UnsafeAlignedOffset.getSize(pageBaseObject, offsetInPage);
offsetInPage += UnsafeAlignedOffset.getUaoSize();
} else {
currentPage = null;
if (reader != null) {
handleFailedDelete();
}
try {
Closeables.close(reader, /* swallowIOException = */ false);
reader = spillWriters.getFirst().getReader(serializerManager);
recordsInPage = -1;
} catch (IOException e) {
// Scala iterator does not handle exception
Platform.throwException(e);
}
}
}
}
if (pageToFree != null) {
freePage(pageToFree);
} finally {
if (pageToFree != null) {
freePage(pageToFree);
}
}
}

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