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Message-Id: <1393223377-5744-7-git-send-email-tuukka.tikkanen@linaro.org> Date: Mon, 24 Feb 2014 08:29:36 +0200 From: Tuukka Tikkanen <tuukka.tikkanen@...aro.org> To: linux-pm@...r.kernel.org, rjw@...ysocki.net Cc: daniel.lezcano@...aro.org, tuukka.tikkanen@...aro.org, linux-kernel@...r.kernel.org Subject: [PATCH 6/7] Cpuidle: Deal with timer expiring in the past Sometimes (fairly often) when the cpuidle menu governor is making a decision about idle state to enter the next timer for the cpu appears to expire in the past. The menu governor expects the expiry to always be in the future and in fact stores the time delta in an unsigned variable. However, when the expiry is in the past, the value returned by tick_nohz_get_sleep_length can be negative. This patch prevents using negative values, instead making the governor return immediately similar to having latency requirement set to 0. Note: As with latency == 0, the return value is 0 with no check to see if the state 0 has been disabled or not. Signed-off-by: Tuukka Tikkanen <tuukka.tikkanen@...aro.org> --- drivers/cpuidle/governors/menu.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index 71b5232..c414468 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -302,8 +302,16 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) if (unlikely(latency_req == 0)) return 0; - /* determine the expected residency time, round up */ + /* + * Determine the expected residency time. If the time is negative, + * a timer interrupt has probably just expired after disabling + * interrupts. Return as quickly as possible in the most shallow + * state possible. tv_nsec is always positive, so only check the + * seconds. + */ t = ktime_to_timespec(tick_nohz_get_sleep_length()); + if (t.tv_sec < 0) + return 0; data->next_timer_us = t.tv_sec * USEC_PER_SEC + t.tv_nsec / NSEC_PER_USEC; -- 1.7.9.5 -- 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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