Messages in this thread | | | Subject | Re: Lockdep message on workqueue_mutex | From | Arjan van de Ven <> | Date | Tue, 22 Aug 2006 14:36:32 +0200 |
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On Tue, 2006-08-22 at 14:10 +0200, Heiko Carstens wrote: > git commit 9b41ea7289a589993d3daabc61f999b4147872c4 causes the lockdep > message below on cpu hotplug (git kernel of today). > > We have: > > cpu_down (takes cpu_add_remove_lock) > [CPU_DOWN_PREPARE] > blocking_notifier_call_chain (takes (cpu_chain).rwsem) > workqueue_cpu_callback (takes workqueue_mutex) > blocking_notifier_call_chain (releases (cpu_chain).rwsem) > [CPU_DEAD] > blocking_notifier_call_chain (takes (cpu_chain).rwsem) > ^^^^^^^^^^^^^^^^^^^^^^^ > -> reverse locking order, since we still hold workqueue_mutex. > > But since all of this is protected by the cpu_add_remove_lock this looks > legal. Well, at least it's safe as long as no other cpu callback function > does anything that will take the workqueue_mutex as well.
so you're saying this locking is entirely redundant ? ;-)
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