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    SubjectRe: [bug] stuck localhost TCP connections, v2.6.26-rc3+

    * Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> wrote:

    > On Mon, 26 May 2008, Ingo Molnar wrote:
    >
    > > there's a hung distcc task on the system, waiting for socket action
    > > forever:
    > >
    > > [root@europe ~]# strace -fp 19578
    > > Process 19578 attached - interrupt to quit
    > > select(5, NULL, [4], [4], {82, 90000} <unfinished ...>
    >
    > Hmm, readfds is NULL isn't it?!? Are you sure you straced the right
    > process?

    yes, i'm stracing the task that is hung unexpectedly.

    > > disturbing that task via strace did not change the state of the
    > > socket - and that's not unexpected as it's a select(). [TCP state
    > > might be affected if strace impacted a recvmsg or a sendmsg wait
    > > directly.]
    >
    > I fail to understand this paragraph due to excessive negation... :-)

    i mean, sometimes a TCP connection can get 'unstuck' if you strace a
    task - that is because the TCP related syscall the task sits in gets
    interrupted. But in this case it's select() which doesnt explicitly take
    the socket, doesnt do any tcp_push_pending_frames() processing, etc. -
    it just its on the socket waitqueue AFAICS. And that's expected.

    Ingo
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