ok, reordering is not a good idea to consider here. But, please note that
if conifgureBlocking wans't synchronized then a statement:
blocking = false
could be "skipped" on compilation level because JMM doesn't guarantee you
that every access to the memory will be "commit" to the main memory.
W dniu piątek, 9 marca 2018 23:20:37 UTC+1 użytkownik John Hening napisał:
>
>
> executor = Executors.newFixedThreadPool(16);
> while(true) {
> SocketChannel connection = serverSocketChannel.accept();
> connection.configueBlocking(false);
> executor.execute(() -> writeTask(connection));
> }
> void writeTask(SocketChannel s){
> s.isBlocking();
> }
>
> public final SelectableChannel configureBlocking(boolean block) throws
> IOException
> {
> synchronized (regLock) {
> ...
> blocking = block;
> }
> return this;
> }
>
>
>
> We see the following situation: the main thread is setting
> connection.configueBlocking(false)
>
> and another thread (launched by executor) is reading that. So, it looks
> like a datarace.
>
> My question is:
>
> 1. Here
> configureBlocking
>
> is synchronized so it behaves as memory barrier. It means that code is ok-
> even if reading/writing to
> blocking
>
> field is not synchronized- reading/writing boolean is atomic.
>
> 2. What if
> configureBlocking
>
> wouldn't be synchronized? What in a such situation? I think that it would
> be necessary to emit a memory barrier because it is theoretically possible
> that setting blocking field could be reordered.
>
> Am I right?
>
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