Messages in this thread | | | Date | Tue, 15 Apr 2008 16:37:28 +0200 | From | Heiko Carstens <> | Subject | Re: 2.6.25-rc9 -- INFO: possible circular locking dependency detected |
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On Tue, Apr 15, 2008 at 07:22:10PM +0530, Gautham R Shenoy wrote: > On Mon, Apr 14, 2008 at 09:35:39PM +0200, Heiko Carstens wrote: > > The problem here is that between register_hotcpu_notifier() and > > get_online_cpus() a cpu might have been hotplugged. > > So on cpu down the registered function might try to undo something that > > wasn't prepared in the first place. > > On cpu up however it will do things twice. Once for the cpus that got > > added between register_hotcpu_notifier() and for_each_online_cpus() > > and then again in the for_each_online_cpus() loop. > > > > Of course all of these scenarios could be fixed in each driver, but that > > would be a lot of duplicated work. Making sure the combination of > > get_online_cpus() and register_hotcpu_notifier() cannot deadlock would > > make things much easier. > > Ah, okay. Thanks for the explanation. > So how about having a new API, > something along the lines of: > > kernel/cpu.c > ------------------------------------------------------ > register_hot_cpu_notifier_init(notifier_name, driver_hotcpu_init_function) > { > mutex_lock(&cpu_add_remove_lock); > get_online_cpus(); > __register_hot_cpu_notifier(notifier_name); > driver_hotcpu_init_function(); > put_online_cpus(); > mutex_unlock(&cpu_add_remove_lock); > } > > drivers/mydriver.c > -------------------------------------------------------------- > driver_hotcpu_init_function() > { > for_each_online_cpus() > perform_subsystem_hotcpu_initialization(); > } > > > driver_init() > { > register_hotcpu_notifier_init(notifier_name, > driver_hotcpu_init_function); > }
That looks fine to me.
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