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    SubjectRe: [BUG 3.12.rc4] Oops: unable to handle kernel paging request during shutdown
    On Mon, Oct 28, 2013 at 11:30 AM, Veaceslav Falico <vfalico@redhat.com> wrote:
    > On Mon, Oct 28, 2013 at 11:23:41AM -0600, Bjorn Helgaas wrote:
    >>
    >> [+cc Veaceslav]
    >>
    >> On Sun, Oct 27, 2013 at 3:24 PM, Greg Kroah-Hartman
    >> <gregkh@linuxfoundation.org> wrote:
    >>>
    >>> On Sun, Oct 27, 2013 at 09:13:29PM +0000, Linus Torvalds wrote:
    >>>>
    >>>> .. and one more case of freeing a delayed work object (likely a kobject
    >>>> again):
    >>>>
    >>>> This time it looks like it's in the PCI layer, freeing the msi irq
    >>>> information.
    >>>>
    >>>> It looks like that code simply does
    >>>>
    >>>> kobject_del(&entry->kobj);
    >>>> kobject_put(&entry->kobj);
    >>>> list_del(&entry->list);
    >>>> kfree(entry);
    >>>>
    >>>> and the problem is that the "entry->kobj" may have *other* references
    >>>> to it, thanks to people accessing it through /sys, so despite doing a
    >>>> kojbect_del/kobject_put(), it's not at all ok to then do a "kfree()"
    >>>> on it. The embedded kobj might still be in use.
    >>>>
    >>>> Afaik, that code should do the kfree() on the kobject in the _release_
    >>>> method, not synchronously like that.
    >>>>
    >>>> We already have a msi_kobj_release(), I'm wondering why that doesn't
    >>>> do the kfree().
    >>>>
    >>>> Bjorn? Yinghai? Greg, comments about that msi kobj usage?
    >>>
    >>>
    >>> Ick, it really should be doing a kfree() in the release only. Bjorn has
    >>> had a bunch of changes in this area recently, perhaps they are in
    >>> linux-next waiting for 3.13, and I've talked to him about getting rid of
    >>> all of the kobjects for msi files, as I don't think it's needed at all.
    >>
    >>
    >> IIRC, you said you might take a look at converting this to attributes
    >> on the train back home, so I haven't looked into it myself :)
    >>
    >>> Bjorn, don't you have a fix for this problem already done somewhere?
    >>
    >>
    >> Yep, this is clearly wrong, and Veaceslav has a patch that moves the
    >> kfree() to the release function. I've been waiting for a consolidated
    >> repost of all his MSI-related fixes, but maybe he's been waiting for
    >> *me*.
    >
    >
    > https://lkml.org/lkml/2013/10/9/170
    >
    > My patchset is ready to be applied, in its v2 state.
    >
    > Except that the bits with kobject_del() (theoretical race) - which are done
    > in your patch "kobject: remove kset from sysfs immediately in
    > kset_unregister()", though I didn't see it accepted.
    >
    > Should I re-send the patchset?

    Can you please repost it? That will be easier for me than digging
    individual messages out of the archives. Thanks, and sorry for my
    confusion.

    Bjorn


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