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Date: Wed, 22 Oct 2014 22:57:25 +0200 (CEST) From: Jiri Kosina <jkosina@...e.cz> To: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, "Rafael J. Wysocki" <rjw@...ysocki.net>, Pavel Machek <pavel@....cz>, Steven Rostedt <rostedt@...dmis.org>, Dave Jones <davej@...hat.com>, Daniel Lezcano <daniel.lezcano@...aro.org>, Nicolas Pitre <nico@...aro.org>, linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org Subject: Re: lockdep splat in CPU hotplug 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@...e.cz> once merging it. Why lockdep produced such an incomplete stacktrace still remains unexplained. Thanks, -- Jiri Kosina SUSE Labs -- 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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