RFR: 8210511: TestSingleWriterSynchronizer can deadlock

[Erik Österlund]

Hi Kim

Looks good.

Thanks,
/Erik

On 2018-09-08 00:47, Kim Barrett wrote:
> Please review this fix of a possible hang by the gtest for
> SingleWriterSynchronizer. The test threads run (without safepoint
> checks) until the driver thread signals them to stop.  If the driver
> thread blocks waiting for a safepoint in os::sleep, that signal will
> never be made.
>
> The fix being made is to add safepoint checks to the test threads,
> avoiding that deadlock.
>
> The readers are also changed to report the number of changed values
> they detected, demonstrating that we're actually testing something.
>
> The time to run the test was reduced from 3sec to 1sec, in the
> interest of saving a few watts in the test farm.
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8210511
>
> Webrev:
> http://cr.openjdk.java.net/~kbarrett/8210511/open.00/
>
> Testing:
> Ran test locally, both in final form and with 100sec runtime.
> mach5 tier1.
>
>