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    SubjectRe: [RFC][PATCH 3/5] timekeeping: Avoid possible deadlock from clock_was_set_delayed
    On 12/11/2013 02:11 PM, John Stultz wrote:
    > As part of normal operaions, the hrtimer subsystem frequently calls
    > into the timekeeping code, creating a locking order of
    > hrtimer locks -> timekeeping locks
    >
    > clock_was_set_delayed() was suppoed to allow us to avoid deadlocks
    > between the timekeeping the hrtimer subsystem, so that we could
    > notify the hrtimer subsytem the time had changed while holding
    > the timekeeping locks. This was done by scheduling delayed work
    > that would run later once we were out of the timekeeing code.
    >
    > But unfortunately the lock chains are complex enoguh that in
    > scheduling delayed work, we end up eventually trying to grab
    > an hrtimer lock.
    >
    > Sasha Levin noticed this in testing when the new seqlock lockdep
    > enablement triggered the following (somewhat abrieviated) message:

    [snip]

    This seems to work for me, I don't see the lockdep spew anymore.

    Tested-by: Sasha Levin <sasha.levin@oracle.com>


    Thanks,
    Sasha


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