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    SubjectRe: next/master boot bisection: next-20190215 on beaglebone-black
    On Wed, Mar 06, 2019 at 10:14:47AM +0000, Guillaume Tucker wrote:
    > On 01/03/2019 23:23, Dan Williams wrote:
    > > On Fri, Mar 1, 2019 at 1:05 PM Guillaume Tucker
    > > <guillaume.tucker@collabora.com> wrote:
    > >
    > > Is there an early-printk facility that can be turned on to see how far
    > > we get in the boot?
    >
    > Yes, I've done that now by enabling CONFIG_DEBUG_AM33XXUART1 and
    > earlyprintk in the command line. Here's the result, with the
    > commit cherry picked on top of next-20190304:
    >
    > https://lava.collabora.co.uk/scheduler/job/1526326
    >
    > [ 1.379522] ti-sysc 4804a000.target-module: sysc_flags 00000222 != 00000022
    > [ 1.396718] Unable to handle kernel paging request at virtual address 77bb4003
    > [ 1.404203] pgd = (ptrval)
    > [ 1.406971] [77bb4003] *pgd=00000000
    > [ 1.410650] Internal error: Oops: 5 [#1] ARM
    > [...]
    > [ 1.672310] [<c07051a0>] (clk_hw_create_clk.part.21) from [<c06fea34>] (devm_clk_get+0x4c/0x80)
    > [ 1.681232] [<c06fea34>] (devm_clk_get) from [<c064253c>] (sysc_probe+0x28c/0xde4)
    >
    > It's always failing at that point in the code. Also when
    > enabling "debug" on the kernel command line, the issue goes
    > away (exact same binaries etc..):
    >
    > https://lava.collabora.co.uk/scheduler/job/1526327
    >
    > For the record, here's the branch I've been using:
    >
    > https://gitlab.collabora.com/gtucker/linux/tree/beaglebone-black-next-20190304-debug
    >
    > The board otherwise boots fine with next-20190304 (SMP=n), and
    > also with the patch applied but the shuffle configs set to n.
    >
    > > Were there any boot *successes* on ARM with shuffling enabled? I.e.
    > > clues about what's different about the specific memory setup for
    > > beagle-bone-black.
    >
    > Looking at the KernelCI results from next-20190215, it looks like
    > only the BeagleBone Black with SMP=n failed to boot:
    >
    > https://kernelci.org/boot/all/job/next/branch/master/kernel/next-20190215/
    >
    > Of course that's not all the ARM boards that exist out there, but
    > it's a fairly large coverage already.
    >
    > As the kernel panic always seems to originate in ti-sysc.c,
    > there's a chance it's only visible on that platform... I'm doing
    > a KernelCI run now with my test branch to double check that,
    > it'll take a few hours so I'll send an update later if I get
    > anything useful out of it.
    >
    > In the meantime, I'm happy to try out other things with more
    > debug configs turned on or any potential fixes someone might
    > have.

    ARM is the only arch that sets ARCH_HAS_HOLES_MEMORYMODEL to 'y'. Maybe the
    failure has something to do with it...

    Guillaume, can you try this patch:

    diff --git a/mm/shuffle.c b/mm/shuffle.c
    index 3ce1248..4a04aac 100644
    --- a/mm/shuffle.c
    +++ b/mm/shuffle.c
    @@ -58,7 +58,8 @@ module_param_call(shuffle, shuffle_store, shuffle_show, &shuffle_param, 0400);
    * For two pages to be swapped in the shuffle, they must be free (on a
    * 'free_area' lru), have the same order, and have the same migratetype.
    */
    -static struct page * __meminit shuffle_valid_page(unsigned long pfn, int order)
    +static struct page * __meminit shuffle_valid_page(unsigned long pfn, int order,
    + struct zone *z)
    {
    struct page *page;

    @@ -80,6 +81,9 @@ static struct page * __meminit shuffle_valid_page(unsigned long pfn, int order)
    if (!PageBuddy(page))
    return NULL;

    + if (!memmap_valid_within(pfn, page, z))
    + return NULL;
    +
    /*
    * ...is the page on the same list as the page we will
    * shuffle it with?
    @@ -123,7 +127,7 @@ void __meminit __shuffle_zone(struct zone *z)
    * page_j randomly selected in the span @zone_start_pfn to
    * @spanned_pages.
    */
    - page_i = shuffle_valid_page(i, order);
    + page_i = shuffle_valid_page(i, order, z);
    if (!page_i)
    continue;

    @@ -137,7 +141,7 @@ void __meminit __shuffle_zone(struct zone *z)
    j = z->zone_start_pfn +
    ALIGN_DOWN(get_random_long() % z->spanned_pages,
    order_pages);
    - page_j = shuffle_valid_page(j, order);
    + page_j = shuffle_valid_page(j, order, z);
    if (page_j && page_j != page_i)
    break;
    }

    --
    Sincerely yours,
    Mike.

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