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    SubjectRe: HPET regression in 2.6.26 versus 2.6.25 -- revert for 2.6.26-rc1 failed
    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);

    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;
    e820_reserve_resources(res_kernel, num_res);

    then (in e820_reserve_resources()):

    for (j = 0; j < nr_res_k; j++) {
    if (!res_kernel[j])
    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.


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      Last update: 2008-08-14 12:07    [W:0.042 / U:12.932 seconds]
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