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    SubjectRe: [PATCH] PM: Acquire device locks on suspend
    On Sat, 5 Jan 2008, Rafael J. Wysocki wrote:

    > On Saturday, 5 of January 2008, Alan Stern wrote:
    > > On Sat, 5 Jan 2008, Rafael J. Wysocki wrote:
    > >
    > > > > Another thing to watch out for: Just in case somebody ends up calling
    > > > > destroy_suspended_device(dev) from within dev's own resume method, you
    > > > > should interchange the resume_device() and the list_move_tail()
    > > > > calls in dpm_resume().
    > > >
    > > > However, if we unregister them all at once after releasing pm_sleep_rwsem,
    > > > that shouldn't be necessary, right?
    > >
    > > It's still necessary, because destroy_suspended_device() still has to
    > > move the device from one list to another. You don't want it to end up
    > > on the dpm_locked list.
    > Hmm. That means we'd have to do the same thing in dpm_power_up() in case
    > someone calls destroy_suspended_device() from resume_device_early(dev).


    > Still, even doing that is not enough, since someone can call
    > destroy_suspended_device() from a .suspend() routine and then the device
    > will end up on a wrong list just as well.

    That should never happen. The whole idea of destroy_suspended_device()
    is that the device couldn't be resumed and in fact should be
    unregistered because it is no longer working or no longer present. A
    suspend routine won't detect this sort of thing since it doesn't try to
    resume the device.

    But it wouldn't hurt to mention in the kerneldoc that
    destroy_suspended_device() is meant to be called only during a system

    Alan Stern

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      Last update: 2008-01-05 22:43    [W:0.019 / U:89.832 seconds]
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