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    SubjectRe: latest -git: hibernate: possible circular locking dependency detected
    On Thu, Aug 21, 2008 at 7:38 PM, Dmitry Adamushko
    <> wrote:
    >> [ INFO: possible circular locking dependency detected ]
    >> 2.6.27-rc4-00003-ga798564 #28


    > this path is triggered as a result of "echo disk > /sys/power/state"

    Yes. That is what I typed.

    > disable_nonboot_cpus() calls cpu_maps_update_being() which takes
    > "cpu_add_remove_lock" (lock-1).
    > If we go down the road cleanup_workqueue_thread() ->
    > flush_cpu_workqueue() will take "cwq->lock" (lock-2).
    > So this should be the second lock.

    > hmm, did you somehow hit "Sysrq + o"?
    > 'cause I don't see any other places (say, with handle_sysrq(k,...)
    > where "k" migth be 'o') from where do_power_off() might have been
    > triggered...

    No. But in my logs I often saw SysRq triggered, even though I didn't
    do it any of these times:

    log-20080821-104053.txt:SysRq : SysRq : Show State
    log-20080821-105541.txt:SysRq : Emergency Sync
    log-20080821-105541.txt:SysRq : Emergency Sync
    log-20080821-105541.txt:SysRq : Power Off
    log-20080821-110514.txt:SysRq : Terminate All Tasks
    log-20080821-111650.txt:SysRq : HELP : loglevel0-8 <6>serial 00:0d: activated
    log-20080821-111650.txt:SysRq : Power Off
    log-20080821-111650.txt:SysRq : Terminate All Tasks
    log-20080821-111650.txt:SysRq : SysRq : <6>serial 00:0d: activated
    log-20080821-120628.txt:SysRq : SysRq : HELP : HELP : <6>serial 00:0d: activated
    log-20080821-120628.txt:SysRq : SysRq : HELP : HELP : <6>serial 00:0d: activated

    (And it seems to pick a random letter too. It even showed the "HELP:"
    line at one point!)

    I have no idea why this happens. Is it possible to trigger SysRq by
    writing data on the other end of the serial console? (Maybe my cable
    is bad or something, but data seems to be going in both directions
    over my serial console.)

    The rest I will not comment on. It also seems unlikely that I will be
    able to test any patches reliably, simply because I see a few
    different kinds of issues on resume :-(



    "The animistic metaphor of the bug that maliciously sneaked in while
    the programmer was not looking is intellectually dishonest as it
    disguises that the error is the programmer's own creation."
    -- E. W. Dijkstra, EWD1036

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