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commit cc5a2f7b upstream.

On some archs, the local clockevent device stops in deep cpuidle states.
The broadcast framework is used to wakeup cpus in these idle states, in
which either an external clockevent device is used to send wakeup ipis
or the hrtimer broadcast framework kicks in in the absence of such a
device. One cpu is nominated as the broadcast cpu and this cpu sends
wakeup ipis to sleeping cpus at the appropriate time. This is the
implementation in the oneshot mode of broadcast.

In periodic mode of broadcast however, the presence of such cpuidle
states results in the cpuidle driver calling tick_broadcast_enable()
which shuts down the local clockevent devices of all the cpus and
appoints the tick broadcast device as the clockevent device for each of
them. This works on those archs where the tick broadcast device is a
real clockevent device.  But on archs which depend...