On Mon, 6 Dec 2021 11:28:16 GMT, Aleksey Shipilev <[email protected]> wrote:
>> There are several thread safety issues in java.net.ServerSocket, issues that
>> go back to at least JDK 1.4.
>>
>> The issue of most concern is async close of a ServerSocket that is initially
>> created unbound and where close may be called at or around the time the
>> underlying SocketImpl is created or the socket is bound.
>>
>> The summary of the changes are:
>>
>> 1. The "impl" field is changed to be final field.
>> 2. The closeLock is renamed to stateLock and is required to change the (now
>> volatile) created, bound or closed fields.
>> 3. The needless synchronization has been removed from xxxSoTimeout and
>> xxxReceiveBufferSize.
>>
>> There are many redundant checks for isClosed() and other state that could be
>> removed. Removing them would subtle change the exception thrown when there
>> are two or more failure conditions. So they are left as is.
>
> src/java.base/share/classes/java/net/ServerSocket.java line 712:
>
>> 710: */
>> 711: public void close() throws IOException {
>> 712: synchronized (stateLock) {
>
> Maybe makes some sense to check `closed` outside the lock here? Looks like we
> don't need to re-acquire the lock for repeated `close()` calls.
That would be okay too although I wouldn't expect it is very common to attempt
to close a ServerSocket more than once (the only scenario that comes to mind is
where there is an async close which triggers a shutdown to server and the
shutdown invokes close too).
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PR: https://git.openjdk.java.net/jdk/pull/6712
