RFR 8160710: Enable Thread to grant VarHandle field access to ThreadLocalRandom/Striped64

[Martin Buchholz]

Looks good!

On Wed, Jan 11, 2017 at 4:48 PM, Paul Sandoz <paul.sandoz at oracle.com> wrote:

> Thanks.
>
> Here is an update:
>
>   http://cr.openjdk.java.net/~psandoz/jdk9/8160710-thread-to-tlr/webrev/
>
> With changes to inline expressions, remove thread group stuff from TLR,
> and do the following in InnocuousForkJoinWorkerThread:
>
>  185     static final class InnocuousForkJoinWorkerThread extends
> ForkJoinWorkerThread {
>  186         /** The ThreadGroup for all InnocuousForkJoinWorkerThreads */
>  187         private static final ThreadGroup innocuousThreadGroup =
>  188                 java.security.AccessController.doPrivileged(
>  189                     new java.security.PrivilegedAction<>() {
>  190                         public ThreadGroup run() {
>  191                             ThreadGroup group =
> Thread.currentThread().getThreadGroup();
>  192                             for (ThreadGroup p; (p =
> group.getParent()) != null; )
>  193                                 group = p;
>  194                             return new ThreadGroup(group, "
> InnocuousForkJoinWorkerThreadGroup");
>  195                         }});
>
> Note: the ThreadGroup constructor also performs a security permission check
>
> Paul.
>
> > On 11 Jan 2017, at 16:12, Doug Lea <dl at cs.oswego.edu> wrote:
> >
> > On 01/11/2017 06:39 PM, Martin Buchholz wrote:
> >> Doug, please try to remember the details of the thread group code.
> >>
> >
> >>    >
> >>    > The threadgroup creation code that uses cheating has always seemed
> fishy to me.  The straightforward
> >>    >
> >>    >     /**
> >>    >      * Returns a new group with the system ThreadGroup (the
> >>    >      * topmost, parent-less group) as parent.
> >>    >      */
> >>    >     static final ThreadGroup createThreadGroup(String name) {
> >>    >         if (name == null)
> >>    >             throw new NullPointerException();
> >>    >         ThreadGroup group = Thread.currentThread().
> getThreadGroup();
> >>    >         for (ThreadGroup p; (p = group.getParent()) != null; )
> >>    >             group = p;
> >>    >         return new ThreadGroup(group, name);
> >>    >     }
> >>    >
> >>    > passes all tests.  That could be wrapped in a doPrivileged, or we
> could add something more principled to ThreadGroup itself.  I don't know
> what the motivations are for the threadgroup code.
> >>    >
> >>
> >
> > There was a some point a problem with using doPrivileged in the
> > context of FJP.commonPool initialization, so we went with the
> > suggestion of using unsafe.
> >
> > And at a different point, we decided to place
> > all non-VarHandle-amenable code into TLR so that it could be
> > replaced all at once when bootstrap problems were addressed.
> >
> > And at a different point (which we hope is Now :-) we can
> > replace the unnecessary prior workarounds.
> >
> > -Doug
> >
> >
> >
>
>