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    SubjectRe: v2.6.26-rc7/cgroups: circular locking dependency
    Peter Zijlstra wrote:
    > On Mon, 2008-06-23 at 00:34 +0900, KOSAKI Motohiro wrote:
    >> CC'ed Paul Jackson
    >>
    >> it seems typical ABBA deadlock.
    >> I think cpuset use cgrou_lock() by mistake.
    >>
    >> IMHO, cpuset_handle_cpuhp() sholdn't use cgroup_lock() and
    >> shouldn't call rebuild_sched_domains().
    >
    > Looks like Max forgot to test with lockdep enabled...
    Hmm, I don't think I actually changed any lock nesting/dependencies. Did I ?
    Oh, I see rebuild_sched_domains() is now called from cpuset hotplug handler.
    I just looked at the comment for rebuild_sched_domains() and it says
    " * Call with cgroup_mutex held. ..." that's why I thought it's safe and it
    worked on the test stations.

    Anyway, we need definitely need to make rebuild_sched_domains() work from the
    hotplug handler.

    > Well, someone should when you change the online map.
    >
    > Max, Paul, can we handle this in update_sched_domains() instead?

    That'd be exactly the same as calling rebuild_sched_domains() outside of the
    cgroup_lock(). So I do not think it'll help. Paul has more info in his reply
    so I'll reply to his email.

    Max


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