6.6-stable review patch. If anyone has any objections, please let me know.
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From: Rafael J. Wysocki rafael.j.wysocki@intel.com
commit a03b2011808ab02ccb7ab6b573b013b77fbb5921 upstream.
When the target residency of the current candidate idle state is greater than the expected time till the closest timer (the sleep length), it does not matter whether or not the tick has already been stopped or if it is going to be stopped. The closest timer will trigger anyway at its due time, so if an idle state with target residency above the sleep length is selected, energy will be wasted and there may be excess latency.
Of course, if the closest timer were canceled before it could trigger, a deeper idle state would be more suitable, but this is not expected to happen (generally speaking, hrtimers are not expected to be canceled as a rule).
Accordingly, the teo_state_ok() check done in that case causes energy to be wasted more often than it allows any energy to be saved (if it allows any energy to be saved at all), so drop it and let the governor use the teo_find_shallower_state() return value as the new candidate idle state index.
Fixes: 21d28cd2fa5f ("cpuidle: teo: Do not call tick_nohz_get_sleep_length() upfront") Cc: All applicable stable@vger.kernel.org Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reviewed-by: Christian Loehle christian.loehle@arm.com Tested-by: Christian Loehle christian.loehle@arm.com Link: https://patch.msgid.link/5955081.DvuYhMxLoT@rafael.j.wysocki Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/cpuidle/governors/teo.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)
--- a/drivers/cpuidle/governors/teo.c +++ b/drivers/cpuidle/governors/teo.c @@ -595,11 +595,8 @@ static int teo_select(struct cpuidle_dri * If the closest expected timer is before the terget residency of the * candidate state, a shallower one needs to be found. */ - if (drv->states[idx].target_residency_ns > duration_ns) { - i = teo_find_shallower_state(drv, dev, idx, duration_ns, false); - if (teo_state_ok(i, drv)) - idx = i; - } + if (drv->states[idx].target_residency_ns > duration_ns) + idx = teo_find_shallower_state(drv, dev, idx, duration_ns, false);
/* * If the selected state's target residency is below the tick length