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Date: Tue, 22 Aug 2006 14:36:32 +0200 From: Arjan van de Ven <arjan@...radead.org> To: Heiko Carstens <heiko.carstens@...ibm.com> Cc: Andrew Morton <akpm@...l.org>, Greg KH <gregkh@...e.de>, Dave Jones <davej@...emonkey.org.uk>, linux-kernel@...r.kernel.org Subject: Re: Lockdep message on workqueue_mutex 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 ? ;-) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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