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    SubjectRe: [2.6.31-rc5] oops: NFS4 client manager kthread...
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    Hi Trond,

    On Mon, Aug 17, 2009 at 2:12 PM, Trond
    Myklebust<Trond.Myklebust@netapp.com> wrote:
    > On Sun, 2009-08-16 at 23:40 +0100, Daniel J Blueman wrote:
    >> After losing and regaining ethernet link a few times with 2.6.31-rc5
    >> [1], I've hit an oops in the NFS4 client manager kthread [2] on my
    >> client with NFS4 homedir mount.
    >>
    >> Do you have a frequent test-case for when the client's manager kthread
    >> gets invoked (with and without succeeding callbacks, due to eg a
    >> firewall)? Server here is unpatched 2.6.30-rc6; I recall seeing
    >> problems when the manager kthread gets invoked, across quite a few
    >> kernel releases, just wasn't lucky enough to catch an oops.
    >>
    >> Oppsing in allow_signal() suggests task state corruption perhaps? I'm
    >> downloading the debug kernel to match up the disassembly and line
    >> numbers, if that helps? This time, the client had no firewall (but
    >> have seen other issues when the callback has failed due to the
    >> firewall).
    >
    > Those aren't Oopses. They are 'soft lockup' warnings. Basically, they're
    > saying that the CPU is getting stuck waiting for a spin lock or a mutex.
    >
    > In this case, it is probably the fact that the state manager is going
    > nuts trying to recover, while the connection to the server keeps coming
    > up and going down.
    >
    > What does 'netstat -t' say when you get into this situation?

    Whoops; it's true the stack-trace comes from the soft-lockup detector.

    There was a single 200s link excursion, but the client didn't recover
    as locks are held and never released it seems; I observe the
    '192.168.1.250-m' NFS4 manager kthread being created and not going
    away, despite IP connectivity with the server being fine after.

    I'll reproduce it with stock 2.6.31-rc6 on the client and get 'netstat
    -t' output.

    Thanks for looking at this!
    Daniel

    > Cheers
    >  Trond
    >
    > --
    > Trond Myklebust
    > Linux NFS client maintainer
    >
    > NetApp
    > Trond.Myklebust@netapp.com
    > www.netapp.com
    >



    --
    Daniel J Blueman
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