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    SubjectRe: [PATCH 0/2] Fix (improve) deadlock condition on module removal netfilter socket option removal
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    On Thu, 2007-09-06 at 03:41 +1000, Rusty Russell wrote:
    > On Wed, 2007-09-05 at 13:08 -0400, Neil Horman wrote:
    > > On Thu, Sep 06, 2007 at 02:13:26AM +1000, Rusty Russell wrote:
    > > > On Wed, 2007-09-05 at 17:22 +0200, Patrick McHardy wrote:
    > > > > But I'm wondering, wouldn't module refcounting alone fix this problem?
    > > > > If we make nf_sockopt() call try_module_get(ops->owner), remove_module()
    > > > > on ip_tables.ko would simply fail because the refcount is above zero
    > > > > (so it would fail at point 3 above). Am I missing something important?
    > > >
    > > > Yes, that seems the correct solution to me, too. ISTR that this code
    > > > predates the current module code.
    > > >
    > > > Rusty.
    > >
    > > Thanks guys-
    > > When I first started looking at this problem I would have agreed with
    > > you, that module reference counting alone would fix the problem. However,
    > > delete_module can work in either a non-blocking or a blocking mode. rmmod
    > > passes O_NONBLOCK to delete module, and so is fine, but modprobe does not.

    > You have this backwards: O_NONBLOCK is the default. That seems to be
    > what everyone wants, although I implemented 'rmmod -w' because it seemed
    > like a good option.

    :-)

    Thanks for keeping me copied. I'll think about the in-kernel module
    situation when I get some time over the weekend - but shout if there's
    an external impact sooner! :-)

    Jon.


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