| Date | Sat, 15 Feb 2014 11:38:28 -0800 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH v2 38/52] drivers/base/topology.c: Fix CPU hotplug callback registration |
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On Fri, Feb 14, 2014 at 01:27:51PM +0530, Srivatsa S. Bhat wrote: > Subsystems that want to register CPU hotplug callbacks, as well as perform > initialization for the CPUs that are already online, often do it as shown > below: > > get_online_cpus(); > > for_each_online_cpu(cpu) > init_cpu(cpu); > > register_cpu_notifier(&foobar_cpu_notifier); > > put_online_cpus(); > > This is wrong, since it is prone to ABBA deadlocks involving the > cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently > with CPU hotplug operations). > > Instead, the correct and race-free way of performing the callback > registration is: > > cpu_notifier_register_begin(); > > for_each_online_cpu(cpu) > init_cpu(cpu); > > /* Note the use of the double underscored version of the API */ > __register_cpu_notifier(&foobar_cpu_notifier); > > cpu_notifier_register_done(); > > > Fix the topology code by using this latter form of callback registration. > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Cc: Ingo Molnar <mingo@kernel.org> > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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