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SubjectRe: HPET regression in 2.6.26 versus 2.6.25 -- revert for 2.6.26-rc1 failed
On Thu, Aug 14, 2008 at 3:04 AM, Bill Fink <billfink@mindspring.com> wrote:
> Hi David,
>
> On Wed, 13 Aug 2008, David Witbrodt wrote:
>
>> [Yinghai, please note that I did not request a patch to revert the
>> problem commit. I was merely experimenting -- on my own time, so
>> you folks would not have to bother -- to see if I could make it
>> work. I should have made that more clear! Having said that, I am
>> glad to test changes of any kind on my machine: reverts, code for
>> debugging or info, experiments, etc.]
>
> I'm not sure Yinghai's revert patch is completely equivalent to
> a revert of the original problematic commit, by a side-by-side
> comparison of the original commit with his recent revert patch,
> but then I don't really know that code at all.
>
> In the original code there was a section (in e820_reserve_resources()):
>
> #ifdef CONFIG_KEXEC
> if (crashk_res.start != crashk_res.end)
> request_resource(res, &crashk_res);
> #endif
>
> If you don't have CONFIG_KEXEC defined in your .config, which is
> probably the case, then you would never request a crashk_res resource.
> But in the code after the original commit, it unconditionally calls
> (in reserve_crashkernel()):
>
> crashk_res.start = crash_base;
> crashk_res.end = crash_base + crash_size - 1;
> insert_resource(&iomem_resource, &crashk_res);
>
> And after Yinghai's revert patch it still does (in reserve_crashkernel()):
>
> crashk_res.start = crash_base;
> crashk_res.end = crash_base + crash_size - 1;
> crashk_res_ptr = &crashk_res;
>
> and (in setup_arch()):
>
> num_res = 3;
> if (crashk_res_ptr) {
> res_kernel[num_res] = crashk_res_ptr;
> num_res++;
> }
> e820_reserve_resources(res_kernel, num_res);
>
> then (in e820_reserve_resources()):
>
> for (j = 0; j < nr_res_k; j++) {
> if (!res_kernel[j])
> continue;
> request_resource(res, res_kernel[j]);
> }
>
> which for j == 3 is:
>
> request_resource(res, &crashk_res);
>
> Now it would appear that the new:
>
> insert_resource(&iomem_resource, &crashk_res);
>
> or new:
>
> request_resource(res, &crashk_res);
>
> should be noops. But if for any reason crash_size is not zero,
> then there could be a difference. I have no idea if this is at all
> significant, but I thought I'd point it out just in case.

why oops ?
if not valid crash kernel size etc is input, crashk_res_ptr will be null

> if (crashk_res_ptr) {
> res_kernel[num_res] = crashk_res_ptr;
> num_res++;
> }

it that is not appended to res_kernel...

YH


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