RFR: jsr166 jdk integration 2018-02

[David Holmes]

Hi Martin,

On 9/02/2018 2:07 PM, Martin Buchholz wrote:
> 
> 
> On Thu, Feb 8, 2018 at 7:39 PM, David Holmes <david.holmes at oracle.com 
> <mailto:david.holmes at oracle.com>> wrote:
> 
>     On 9/02/2018 11:19 AM, Martin Buchholz wrote:
> 
>         http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/overview.html
>         <http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/overview.html>
> 
>         8190324: ThreadPoolExecutor should not specify a dependency on
>         finalization
>         http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/ThreadPoolExecutor-finalize/index.html
>         <http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/ThreadPoolExecutor-finalize/index.html>
>         https://bugs.openjdk.java.net/browse/JDK-8190324
>         <https://bugs.openjdk.java.net/browse/JDK-8190324>
> 
> 
>     Looks okay.
> 
>         Another set of uninteresting changes, some suggested by intellij:
> 
>         8195590: Miscellaneous changes imported from jsr166 CVS 2018-02
>         http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/miscellaneous/index.html
>         <http://cr.openjdk.java.net/~martin/webrevs/jdk/jsr166-integration/miscellaneous/index.html>
>         https://bugs.openjdk.java.net/browse/JDK-8195590
>         <https://bugs.openjdk.java.net/browse/JDK-8195590>
> 
> 
>     Hmmmm ... a summary of changes in the bug report would be nice.
> 
> 
> Done.
> 
>     I don't find the addition of reachability fences uninteresting
>     though. Why are they needed in those specific cases?
> 
> 
> perhaps the standard should be for every method of a class with a 
> finalizer to have reachabilityFence(this) at the end?
> 
> Imagine
> 
> newSingleThreadExecutor().execute(someTask);
> 
> Is is unlikely but possible for the "instant garbage" executor to be 
> finalized while super.execute is in progress, causing failure with 
> RejectedExecutionException because the delegatee is already shutdown.

Wow! DelegatedExecutorService doesn't even have a finalize() method that 
does a shutdown. So we have to put the reachabilityFence in it to 
prevent the delegatee from becoming unreachable due to the delegator 
becoming unreachable!

This whole notion that "this" can be unreachable whilst a method on it 
is still executing is just broken - it's an unusable programming model. 
Any code that does "new Foo().bar()" could fail unless Foo.bar() has a 
reachability fence in it. :( Sheesh!

Cheers,
David