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Rafael J. Wysocki authored
Commit 87c9fe6e (cpuidle: menu: Avoid selecting shallow states with stopped tick) missed the case when the target residencies of deep idle states of CPUs are above the tick boundary which may cause the CPU to get stuck in a shallow idle state for a long time. Say there are two CPU idle states available: one shallow, with the target residency much below the tick boundary and one deep, with the target residency significantly above the tick boundary. In that case, if the tick has been stopped already and the expected next timer event is relatively far in the future, the governor will assume the idle duration to be equal to TICK_USEC and it will select the idle state for the CPU accordingly. However, that will cause the shallow state to be selected even though it would have been more energy-efficient to select the deep one. To address this issue, modify the governor to always use the time till the closest timer event instead of the predicted idle duration if the latter is less than the tick period length and the tick has been stopped already. Also make it extend the search for a matching idle state if the tick is stopped to avoid settling on a shallow state if deep states with target residencies above the tick period length are available. In addition, make it always indicate that the tick should be stopped if it has been stopped already for consistency. Fixes: 87c9fe6e (cpuidle: menu: Avoid selecting shallow states with stopped tick) Reported-by: Leo Yan <leo.yan@linaro.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: 4.17+ <stable@vger.kernel.org> # 4.17+ Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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