RFR(s): [aix]: 8182984: [aix] Make stack traces independent on successful vm initialization

[Volker Simonis]

Hi Thomas,

the change looks good. Following just a little nit-picking:

os_aix.cpp
- you can also remove the comment "133 // Query dimensions of the
stack of the calling thread."

porting_aix.cpp
- the comment "base, high" should be on the line:
 856   //    |         ---------------------   __pi_stackend
instead of:
 852   // high addr    ---------------------

- why do we need the field 'address high' which is merely an alias for
'base' ? I'd remove it.

There's no need for a new webrev if you agree with my suggestions :)

Thank you and best regards,
Volker


On Wed, Jun 28, 2017 at 12:22 PM, Thomas Stüfe <thomas.stuefe at gmail.com> wrote:
> Hi all,
>
> please review, at your convenience, the following AIX-only fix:
>
> Issue: https://bugs.openjdk.java.net/browse/JDK-8182984
> Webrev:
> http://cr.openjdk.java.net/~stuefe/webrevs/8182984-aix-better-stacktraces/webrev.00/webrev/
>
> In short, it improves the chances of getting better callstacks if the VM
> crashes or asserts before os::init() ran or if os::init() ran into an error.
>
> Details:
>
> callstack printing is implemented in our porting layer
> (porting_aix.hpp/cpp), in
> "AixNativeCallstack::print_callstack_for_context()".
>
> This change makes this independent from VM infrastructure (it should be,
> because the porting layer should be below the hotspot and should not have
> dependencies into it).
>
> For one, it is not necessary to use Thread::current() to get the current
> threads stack bounds, because that requires pthread TLS being initialized
> successfully and a current Thread* to exist. For the purpose of stack trace
> printing, we can just call pthread_getthrds_np().
>
> Then, we use os::vm_page_size() to align the lower stack boundary to the
> stack page size (to place our guard pages later). This is a hotspot
> implementation detail and does not have to be done in the porting layer, but
> should be moved upward to os::current_stack_size().
>
> Thank you for reviewing,
>
> Kind Regards, Thomas