RFR(XXS): 8077392 and 8131715 - fix for hang in Contended Locking "fast enter" bucket

[David Holmes]

Hi Dan,

Couldn't pass up the chance to review this - truly great debugging here!

The changes of course look good.

I was surprised to notice that before this fix the Lock argument (which 
should be lower-case lock if you don't mind adjusting that) was actually 
unused in quick_enter! So one has to wonder why it was passed in.

Cheers,
David



On 23/03/2016 6:41 AM, Daniel D. Daugherty wrote:
> Greetings,
>
> I have fixes for the following two bugs:
>
>      JDK-8077392 Stream fork/join tasks occasionally fail to complete
>      https://bugs.openjdk.java.net/browse/JDK-8077392
>
>      JDK-8131715 backout the fix for JDK-8079359 when JDK-8077392 is fixed
>      https://bugs.openjdk.java.net/browse/JDK-8131715
>
> Both fixes are very, very small and will be bundled together in the
> same changeset for obvious reasons.
>
> Here is the webrev URL:
>
> http://cr.openjdk.java.net/~dcubed/8077392_8131715-webrev/0-jdk9-hs-rt/
>
> While the fix for JDK-8077392 is a simple 1-liner, the explanation of
> the race is much, much longer. I've attached the detailed evaluation
> to this RFR; it is a copy of the same note that I added to
> https://bugs.openjdk.java.net/browse/JDK-8077392, but the attached
> copy has all the indentation white space intact. I don't know why
> JBS likes to reformat the notes, but it does... :-(
>
> Testing:
>
> - the original failing test is running in a parallel stress config
>    on my Solaris X64 server; just under 23 hours and just under
>    3000 iterations without a failure in either instance; I'm planning
>    to let the stress run go for at least 72 hours.
> - RT/SVC nightly equivalent (in progress)
>
> As always, comments, suggestions and/or questions are welcome.
>
> Dan