RFR(xs): 8187028: [aix] Real thread stack size may be up to 64K smaller than requested one

[Volker Simonis]

Hi Thomas,

it would be of course interesting to know the real reason for this
behavior. Maybe that could  be used to predict the variation and fix
it more accurately.

But for the time being, your fix is acceptable so you can consider it reviewed.

Thanks for fixing this,
Volker

On Thu, Aug 31, 2017 at 12:08 PM, Thomas Stüfe <thomas.stuefe at gmail.com> wrote:
> Hi all,
>
> please review this change:
>
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8187028
>
> change:
> http://cr.openjdk.java.net/~stuefe/webrevs/8187028-aix-Real-thread-stack-size-may-be-up-to-64K-smaller-than-requested-one/webrev.00/webrev/
>
> The issue is that on AIX, pthread library seems to have a bug where it
> sometimes gives us less thread stack space than we requested (a variable
> amount, but seems to be 0..64K). This may cause intermittent stack overflow
> errors if the stacks are very small to begin with.
>
> The workaround is to add 64K to the requested stack size to account for the
> fact that the OS may give us up to 64K less stack.
>
> Also, improved logging.
>
> Thanks, Thomas