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    SubjectRe: [bug, netconsole, SLUB] BUG skbuff_head_cache: Poison overwritten

    * Vegard Nossum <> wrote:

    > On Fri, Jul 18, 2008 at 1:52 AM, Ingo Molnar <> wrote:
    > > If only we had some kernel technology that could track and validate
    > > memory accesses, and point out the cases where we access uninitialized
    > > memory, just like Valgrind?
    > >
    > > ... something like kmemcheck? ;-)
    > Cool :)
    > > So i booted that box with tip/master and kmemcheck enabled. (plus a few
    > > fixlets to make networking allocations be properly tracked by
    > > kmemcheck.)
    > >
    > > It was a slow bootup and long wait, but it gave a few hits here:
    > Hm, if you think it was that slow, I am suspecting you were also using
    > SLUB debugging.


    # CONFIG_SLUB_DEBUG is not set

    > This can actually be negative, since now SLUB will access the objects
    > (+redzone +padding) and possibly trick kmemcheck into thinking they
    > were initialized in the first place.
    > But what we are really looking for is "read from freed memory"
    > messages. So I would actually recommend this: Disable kmemcheck's
    > reporting of uninitialized memory, simply to make it easier to spot
    > the "freed" messages more easily.
    > Maybe something like this (warning: whitespace-munged):

    ok, applied this too.

    > If this only happens during boot, it would also be a good idea to
    > simply reboot the machine a lot...

    yeah, i've got a script for that. Will try it overnight.


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