Re: [patch 1/2] x86_64 page fault NMI-safe

Steven Rostedt
2010-07-16T12:55:07Z

On Fri, 2010-07-16 at 14:00 +0200, Frederic Weisbecker wrote:
> On Thu, Jul 15, 2010 at 07:51:55AM -0700, Linus Torvalds wrote:

>
> Such new page table created that might race is only about top level page
> right? Otherwise it wouldn't race since the top level entries are shared
> and then updates inside lower level pages are naturally propagated, if
> I understood you well.
>
> So, if only top level pages that gets added can generate such lazily
> mapping update, I wonder why I experienced this fault everytime with
> my patches.
>
> I allocated 8192 bytes per cpu in a x86-32 system that has only 2 GB.
> I doubt there is a top level page table update there at this time with
> such a small amount of available memory. But still it faults once on
> access.
>
> I have troubles to visualize the race and the problem here.
>

A few trace_printks and a tracing_off() on fault would probably show
exactly what was happening ;-)

-- Steve