Messages in this thread | | | Date | Wed, 22 Oct 2014 22:57:25 +0200 (CEST) | From | Jiri Kosina <> | Subject | Re: lockdep splat in CPU hotplug |
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On Wed, 22 Oct 2014, Paul E. McKenney wrote:
> rcu: More on deadlock between CPU hotplug and expedited grace periods > > Commit dd56af42bd82 (rcu: Eliminate deadlock between CPU hotplug and > expedited grace periods) was incomplete. Although it did eliminate > deadlocks involving synchronize_sched_expedited()'s acquisition of > cpu_hotplug.lock via get_online_cpus(), it did nothing about the similar > deadlock involving acquisition of this same lock via put_online_cpus(). > This deadlock became apparent with testing involving hibernation. > > This commit therefore changes put_online_cpus() acquisition of this lock > to be conditional, and increments a new cpu_hotplug.puts_pending field > in case of acquisition failure. Then cpu_hotplug_begin() checks for this > new field being non-zero, and applies any changes to cpu_hotplug.refcount. >
Yes, this works. FWIW, please feel free to add
Reported-and-tested-by: Jiri Kosina <jkosina@suse.cz>
once merging it.
Why lockdep produced such an incomplete stacktrace still remains unexplained.
Thanks,
-- Jiri Kosina SUSE Labs
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