Re: [patch 04/41] cpu ops: Core piece for generic atomic per cpu operations

Mike Travis
2008-06-17T14:21:20Z

Rusty Russell wrote:
> On Tuesday 17 June 2008 00:52:08 Christoph Lameter wrote:
>> On Sun, 15 Jun 2008, Rusty Russell wrote:
>>>> 3. Some hooks for arches to override particular behavior as needed.
>>>> F.e. IA64 allocates percpu structures in a special way. x86_64
>>>> needs to do some tricks for the pda etc etc.
>>> IA64 is going to need some work, since dynamic percpu addresses won't be
>>> able to use their pinned TLB trick to get the local version.
>> The ia64 hook could simply return the address of percpu area that
>> was reserved when the per node memory layout was generated (which happens
>> very early during node bootstrap).
>
> Apologies, this time I read the code. I thought IA64 used the pinned TLB area
> to access per-cpu vars under some circumstances, but they only do that via an
> arch-specific macro.
>
> So creating new congruent mappings to expand the percpu area(s) is our main
> concern now?
>
> Rusty.

Not exactly. Getting the system to not panic early in the boot (before
x86_64_start_kernel()) is the primary problem right now. This happens
in the tip tree with the change to use zero-based percpu offsets. It
gets much farther on the linux-next tree.

Thanks,
Mike