Messages in this thread | | | From | Rusty Russell <> | Subject | Re: 2.6.32-rc5-mmotm1101 - lockdep whinge during early boot | Date | Thu, 5 Nov 2009 19:41:03 +1030 |
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On Thu, 5 Nov 2009 02:41:24 am Valdis.Kletnieks@vt.edu wrote: [ 0.344147] swapper/1 is trying to acquire lock: > [ 0.344154] (cpu_add_remove_lock){+.+.+.}, at: [<ffffffff8103c222>] cpu_maps_update_begin+0x12/0x14 > [ 0.344174] > [ 0.344175] but task is already holding lock: > [ 0.344183] (setup_lock){+.+.+.}, at: [<ffffffff81078755>] stop_machine_create+0x12/0x9b > [ 0.344200] > [ 0.344201] which lock already depends on the new lock.
Hi Vladis!
Sigh. I always find reading these a complete mindfuck.
stop_machine_create: setup_lock then cpu_add_remove_lock (in create_workqueue_key() -> cpu_maps_update_begin()) clocksource_done_booting: clocksource_mutex then setup_lock (in stop_machine_create(), as above) cpu_up: cpu_add_remove_lock then clocksource_mutex (in mark_tsc_unstable() -> clocksource_change_rating())
AFAICT this is our circular dependency. But I'm no closer to knowing how to solve it.
Oleg (CC'd) made workqueues use cpu_maps_update_begin() instead of the more obvious get_online_cpus() in 3da1c84c00c7e5f. Reverting that seems like a bad idea.
Or, if the clocksource list wasn't ordered, we could change the rating without a lock.
Either way, the locking shark is well and truly jumped... Rusty.
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