Re: [vs-plain] Re: [PATCH] mm: larger stack guard gap, between vmas

From: John Haxby
Date: Tue Jul 04 2017 - 08:27:28 EST

On 04/07/17 00:55, Ben Hutchings wrote:
> Unfortunately these regressions have not been completely fixed by
> switching to Hugh's fix.
> Firstly, some Rust programs are crashing on ppc64el with 64 KiB pages.
> Apparently Rust maps its own guard page at the lower limit of the stack
> (determined using pthread_getattr_np() and pthread_attr_getstack()). I
> don't think this ever actually worked for the main thread stack, but it
> now also blocks expansion as the default stack size of 8 MiB is smaller
> than the stack gap of 16 MiB. Would it make sense to skip over
> PROT_NONE mappings when checking whether it's safe to expand?
> Secondly, LibreOffice is crashing on i386 when running components
> implemented in Java. I don't have a diagnosis for this yet.

We found that we needed f4cb767d76cf ("mm: fix new crash in
unmapped_area_topdown()") Apologies if you've already covered that.

This may be needed in addition to the other patch you proposed.