From 9c4b2867ed7c8c8784dd417ffd16e705e81eb145 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Thu, 14 Jan 2016 23:24:22 +0100 Subject: [PATCH] cpuidle: menu: Fix menu_select() for CPUIDLE_DRIVER_STATE_START == 0 Commit a9ceb78bc75c (cpuidle,menu: use interactivity_req to disable polling) exposed a bug in menu_select() causing it to return -1 on systems with CPUIDLE_DRIVER_STATE_START equal to zero, although it should have returned 0. As a result, idle states are not entered by CPUs on those systems. Namely, on the systems in question data->last_state_idx is initially equal to -1 and the above commit modified the condition that would have caused it to be changed to 0 to be less likely to trigger which exposed the problem. However, setting data->last_state_idx initially to -1 doesn't make sense at all and on the affected systems it should always be set to CPUIDLE_DRIVER_STATE_START (ie. 0) unconditionally, so make that happen. Fixes: a9ceb78bc75c (cpuidle,menu: use interactivity_req to disable polling) Reported-and-tested-by: Sudeep Holla Signed-off-by: Rafael J. Wysocki --- drivers/cpuidle/governors/menu.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index 7b0971d97cc3..be0bae0b41e9 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -294,8 +294,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) data->needs_update = 0; } - data->last_state_idx = CPUIDLE_DRIVER_STATE_START - 1; - /* Special case when user has set very strict latency requirement */ if (unlikely(latency_req == 0)) return 0; @@ -326,14 +324,19 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) if (latency_req > interactivity_req) latency_req = interactivity_req; - /* - * We want to default to C1 (hlt), not to busy polling - * unless the timer is happening really really soon. - */ - if (interactivity_req > 20 && - !drv->states[CPUIDLE_DRIVER_STATE_START].disabled && - dev->states_usage[CPUIDLE_DRIVER_STATE_START].disable == 0) + if (CPUIDLE_DRIVER_STATE_START > 0) { + data->last_state_idx = CPUIDLE_DRIVER_STATE_START - 1; + /* + * We want to default to C1 (hlt), not to busy polling + * unless the timer is happening really really soon. + */ + if (interactivity_req > 20 && + !drv->states[CPUIDLE_DRIVER_STATE_START].disabled && + dev->states_usage[CPUIDLE_DRIVER_STATE_START].disable == 0) + data->last_state_idx = CPUIDLE_DRIVER_STATE_START; + } else { data->last_state_idx = CPUIDLE_DRIVER_STATE_START; + } /* * Find the idle state with the lowest power while satisfying -- 2.30.2