RFR(S): 8020753: pthread_get_stacksize_np() workaround for OS X 10.9

[Gerard Ziemski]

Please review this proposed workaround for OS X 10.9 (Mavericks)

Description:

On Mac Os X 10.9 (Mavericks) the pthread_get_stacksize_np() API returns 
128 pages for both main (primodial, primary) and secondary threads, when 
in fact 2048 pages are available for the main thread. 
pthread_get_stacksize_np() correctly returns 2048 pages for main thread 
on 10.6, 10.7 and 10.8 and probably all previous OS X versions.

An issue has been filed with Apple, but in the meantime we need to 
substitute 2048 pages whenever pthread_get_stacksize_np() returns 
anything else (ie. 128) on main thread.

The workaround uses hardcoded value of 2048 pages for main thread, because:

1. The correct value can in fact be found at runtime using signals 
(please see my test case attached to the bug's JDK issue), however, such 
code needs signal handlers and also takes about 3.5 ms, so it's probably 
not a viable solution.

2. We could also look-up OS X version at runtime to only use the 
workaround for 10.9, but that requires parsing an xml file, looking for 
a value that is internationalized, so it's non trivial (though might be 
doable assuming the time to execute is low enough)

3. All JDK8 supported OS X versions (ie. 10.7, 10.8) return 2048.

In the future, this workaround might need to be revisited (ie. 2), but I 
believe that it's reasonable for now, though I would love to hear others 
opinions on this.


Testing:

In progress...


References:

http://cr.openjdk.java.net/~iklam/8020753/ziemski_rev1/
https://bugs.openjdk.java.net/browse/JDK-8020753


cheers