Messages in this thread | | | Subject | Re: INFO: possible circular locking dependency at cleanup_workqueue_thread | From | Johannes Berg <> | Date | Fri, 22 May 2009 12:46:06 +0200 |
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On Tue, 2009-05-19 at 20:51 +0200, Oleg Nesterov wrote:
> > > > Anyway, you can have a deadlock like this: > > > > > > > > CPU 3 CPU 2 CPU 1 > > > > suspend/hibernate > > > > something: > > > > rtnl_lock() device_pm_lock() > > > > -> mutex_lock(&dpm_list_mtx) > > > > > > > > mutex_lock(&dpm_list_mtx) > > > > > > > > linkwatch_work > > > > -> rtnl_lock() > > > > disable_nonboot_cpus() > > > > > > let's suppose disable_nonboot_cpus() does not take cpu_add_remove_lock, > > > > > > > -> flush CPU 3 workqueue > > > > > > in this case the deadlock is still here? > > > > > > We can't flush because we hold the lock (dpm_list_mtx) which depends > > > on another lock taken by work->func(), the "classical" bug with flush. > > > > > > No? > > > > Yeah, it looks like cpu_add_remove_lock doesn't make a difference... > > It's just lockdep reporting a longer chain that also leads to a > > deadlock. > > So. we should not call cpu_down/disable_nonboot_cpus under device_pm_lock(). > > At first glance this was changed by > > PM: Change hibernation code ordering > 4aecd6718939eb3c4145b248369b65f7483a8a02 > > PM: Change suspend code ordering > 900af0d973856d6feb6fc088c2d0d3fde57707d3 > > commits. Rafael, could you take a look?
I just arrived at the same conclusion, heh. I can't say I understand these changes though, the part about calling the platform differently may make sense, but calling why disable non-boot CPUs at a different place?
johannes [unhandled content-type:application/pgp-signature] | |