Github user sarutak commented on a diff in the pull request: https://github.com/apache/spark/pull/2019#discussion_r16632233 --- Diff: core/src/main/scala/org/apache/spark/network/Connection.scala --- @@ -263,14 +282,20 @@ class SendingConnection(val address: InetSocketAddress, selector_ : Selector, val DEFAULT_INTEREST = SelectionKey.OP_READ + var alreadyReading = false + override def registerInterest() { // Registering read too - does not really help in most cases, but for some // it does - so let us keep it for now. - changeConnectionKeyInterest(SelectionKey.OP_WRITE | DEFAULT_INTEREST) + changeConnectionKeyInterest( + SelectionKey.OP_WRITE | (if (!alreadyReading) { + alreadyReading = true + DEFAULT_INTEREST + } else { 0 })) --- End diff -- Yes, we use blocking IO. And I had a misunderstanding. SocketChannel#read blocks the other thread which try to call SocketChannel#read on the same instance so unregistering OP_READ is wrong. So, we should resolve race condition using another way because a thread registering OP_READ can call SocketChannel#close in SendingConnection#read during a thread registering OP_WRITE calls SocketChannel#write in SendingConnection#write.
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