RFR: 8315351: Rid synchronization in PipedInputStream.close() in favour of benign race

[Vyom Tewari]

On Wed, 30 Aug 2023 09:49:39 GMT, Sergey Tsypanov <stsypanov at openjdk.org> wrote:

> Assuming that the value written into `in` is always `-1` we can rid synchronized block in favour of guarding `in = - 1` with writing into volatile `closedByReader `:
> 
> public void close() throws IOException {
>     closedByReader = true;
>     synchronized (this) {
>         in = -1;
>     }
> }
> 
> -->
> 
> public void close() throws IOException {
>     in = -1;
>     closedByReader = true;
> }

src/java.base/share/classes/java/io/PipedInputStream.java line 448:

> 446:     @Override
> 447:     public void close() throws IOException {
> 448:         in = -1;

I am not sure if this is write thing to do, variable 'in' is accessed from "synchronized void receive(byte[] b, int off, int len)". What if  'close()' is called simultaneously ?.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15486#discussion_r1310102524