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    SubjectRe: Linux 2.6.17-rc2 - notifier chain problem?
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    On Mon, 2006-04-24 at 15:03 -0700, Andrew Morton wrote:
    > Chandra Seetharaman <sekharan@us.ibm.com> wrote:
    > >
    > > Thanks for the steps. With that i was able to reproduce the problem and
    > > i found the bug.
    > >
    > > While i go ahead and generate the patch, i wanted to hear if my
    > > conclusion is correct.
    > >
    > > The problem is due to the fact that most notifier registrations
    > > incorrectly use __devinitdata to define the callback structure, as in:
    > >
    > > static struct notifier_block __devinitdata hrtimers_nb = {
    > > .notifier_call = hrtimer_cpu_notify,
    > > };
    > >
    > > devinitdata'd data is not _expected to be available_ after the
    > > initialization(unless CONFIG_HOTPLUG is defined).
    > >
    > > I do not know how it was working until now :), anybody has a theory that
    > > can explain it (or my conclusion is wrong) ?
    >
    > That sounds right. There are several __devinitdata notifier_blocks in the
    > tree - please be sure to check them all.

    Yes, I am covering all notifier blocks.

    Another issue... many of the notifier callback functions are marked as
    init calls (__cpuinit, __devinit etc.,) as in:

    static int __cpuinit pageset_cpuup_callback(struct notifier_block *nfb,
    unsigned long action,
    void *hcpu)

    I am generating a separate patch to take care of those too.
    >
    > btw, it'd be pretty trivial to add runtime checking for this sort of thing:
    >
    > int addr_in_init_section(void *addr)
    > {
    > return addr >= __init_begin && addr < __init_end;
    > }

    I will add this to kernel/sys.c, and put a BUG_ON to check for both the
    notifier block and the callback function.

    BTW, which header file you want me to export this through ?
    >
    > (x86-specific)
    > (need to add __init_end to vmlinux.lds.S)

    I see __init_end in arch/i386/kernel/vmlinux.lds.S.

    >
    > then we could use that to check various things in various places...
    --

    ----------------------------------------------------------------------
    Chandra Seetharaman | Be careful what you choose....
    - sekharan@us.ibm.com | .......you may get it.
    ----------------------------------------------------------------------


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