Hi,

Cool, thanks.  The following is based on this and fixes the problem for
me on PPC64 ie. the !CONFIG_STACK_GROWSUP case. 

Thanks! Seeing the original setting of EXTRA_STACK_VM_PAGES is more or
less random, I wonder if we should round EXTRA_STACK_VM_SIZE up to 128kB
(or even down to 64kB) so it operates better with > 4kB pages.

But in the end its probably of little use for the default OVERCOMMIT_GUESS
setting, so the main thing is we dont terminate processes incorrectly.

Acked-by: Anton Blanchard <redacted>

Anton