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    SubjectRe: Fw: [PATCH -mm] workqueue: debug possible endless loop in cancel_rearming_delayed_work
    On Thu, Apr 19, 2007 at 02:21:22PM +0400, Oleg Nesterov wrote:
    > On 04/19, Andrew Morton wrote:
    > >
    > > Begin forwarded message:
    > >
    > > Date: Thu, 19 Apr 2007 08:54:04 +0200
    > > From: Jarek Poplawski <>
    > > To:
    > > Cc: Ingo Molnar <>
    > > Subject: [PATCH -mm] workqueue: debug possible endless loop in cancel_rearming_delayed_work

    At first I didn't spotted your thread is "independent" and
    from your second message it seems you didn't receive all, you
    expected. I wonder, if there is a need and possibility to add
    somewhere (I would prefer Linus' tree git's http frontend)
    addresses of developers (but not maintainers), who are
    interested in CC-ing about some files' patches?.

    > Yes. It would be better to use cancel_work_sync() instead of flush_workqueue()
    > to make this less possible (because cancel_work_sync() doesn't need to wait for
    > the whole ->worklist), but we can't.
    > > Maybe this patch could check, if I'm not dreaming...
    > Also: cancel_rearming_delayed_work() will hang if it (or cancel_delayed_work())
    > was already called.
    > I had some ideas how to make this interface reliable, but I can't see how to do
    > this without uglification of the current code.

    For some time I thought about using a flag (isn't there
    one available after NOAUTOREL?), e.g. WORK_STRUCT_CANCEL,
    as a sign:

    - for a workqueue code: that the work shouldn't be queued,
    nor executed, if possiblei, at first possible check.

    - for a work function: to stop execution as soon as possible,
    even without completing the usual job, at first possible check.

    There would be a question, whether the flag should be changed
    under a lock for exact synchronisation.

    Jarek P.

    PS: I hope there is no reason against going with this to lkml
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