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    SubjectRe: network driver usage count
    Date
    David Miller <davem@davemloft.net> writes:

    > From: Wagner Ferenc <wferi@niif.hu>
    > Date: Wed, 21 Nov 2007 23:16:59 +0100
    >
    >> Hmm, that would warrant nuking all the reference counts on every
    >> driver.
    >
    > That's not true. When packets are in flight, references go
    > to the device and the device cannot be unloaded until those
    > references get dropped.

    I'm trying to understand it. Do you mean that the "usage count" in
    the lsmod output does not express the user's view of a piece of *ware
    being in use, but rather the number of internal kernel references to
    it, which would become invalid should that piece disappear? Where the
    former "invalidily" means some undetectable and uncorrectable
    inconsistency in the kernel data structures, which leads to a kernel
    crash.

    > This behavior makes sense because otherwise you have to figure
    > out the myriad of references (each ipv4 address, each ipv6
    > address, routes, ARP entries, etc.) just to perform such a
    > simple operation.

    Yes, that's the user's idea of a network device being in use. It can
    get hairy indeed.

    > If you do not mean to unload the device, simply do not do it.

    Now I know...
    --
    Thanks for taking the time,
    Feri.
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