From 01e04f466e12e883907937eb04a9010533363f55 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Fri, 27 Feb 2015 00:39:21 +0100 Subject: idle / sleep: Avoid excessive disabling and enabling interrupts Disabling interrupts at the end of cpuidle_enter_freeze() is not useful, because its caller, cpuidle_idle_call(), re-enables them right away after invoking it. To avoid that unnecessary back and forth dance with interrupts, make cpuidle_enter_freeze() enable interrupts after calling enter_freeze_proper() and drop the local_irq_disable() at its end, so that all of the code paths in it end up with interrupts enabled. Then, cpuidle_idle_call() will not need to re-enable interrupts after calling cpuidle_enter_freeze() any more, because the latter will return with interrupts enabled, in analogy with cpuidle_enter(). Reported-by: Lorenzo Pieralisi Signed-off-by: Rafael J. Wysocki Acked-by: Peter Zijlstra (Intel) --- kernel/sched/idle.c | 1 - 1 file changed, 1 deletion(-) (limited to 'kernel') diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 94b2d7b88a27..f59198bda1bf 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -116,7 +116,6 @@ static void cpuidle_idle_call(void) */ if (idle_should_freeze()) { cpuidle_enter_freeze(); - local_irq_enable(); goto exit_idle; } -- cgit v1.2.3-59-g8ed1b From dfcacc154fb38fdb2c243c3dbbdc1f26a64cedc8 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Mon, 2 Mar 2015 22:25:37 +0100 Subject: cpuidle: Clean up fallback handling in cpuidle_idle_call() Move the fallback code path in cpuidle_idle_call() to the end of the function to avoid jumping to a label in an if () branch. Signed-off-by: Rafael J. Wysocki --- kernel/sched/idle.c | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-) (limited to 'kernel') diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index f59198bda1bf..84b93b68482a 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -124,20 +124,8 @@ static void cpuidle_idle_call(void) * Fall back to the default arch idle method on errors. */ next_state = cpuidle_select(drv, dev); - if (next_state < 0) { -use_default: - /* - * We can't use the cpuidle framework, let's use the default - * idle routine. - */ - if (current_clr_polling_and_test()) - local_irq_enable(); - else - arch_cpu_idle(); - - goto exit_idle; - } - + if (next_state < 0) + goto use_default; /* * The idle task must be scheduled, it is pointless to @@ -195,6 +183,19 @@ exit_idle: rcu_idle_exit(); start_critical_timings(); + return; + +use_default: + /* + * We can't use the cpuidle framework, let's use the default + * idle routine. + */ + if (current_clr_polling_and_test()) + local_irq_enable(); + else + arch_cpu_idle(); + + goto exit_idle; } /* -- cgit v1.2.3-59-g8ed1b From ef2b22ac540c018bd574d1846ab95b9bfcf38702 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Mon, 2 Mar 2015 22:26:55 +0100 Subject: cpuidle / sleep: Use broadcast timer for states that stop local timer Commit 381063133246 (PM / sleep: Re-implement suspend-to-idle handling) overlooked the fact that entering some sufficiently deep idle states by CPUs may cause their local timers to stop and in those cases it is necessary to switch over to a broadcast timer prior to entering the idle state. If the cpuidle driver in use does not provide the new ->enter_freeze callback for any of the idle states, that problem affects suspend-to-idle too, but it is not taken into account after the changes made by commit 381063133246. Fix that by changing the definition of cpuidle_enter_freeze() and re-arranging of the code in cpuidle_idle_call(), so the former does not call cpuidle_enter() any more and the fallback case is handled by cpuidle_idle_call() directly. Fixes: 381063133246 (PM / sleep: Re-implement suspend-to-idle handling) Reported-and-tested-by: Lorenzo Pieralisi Signed-off-by: Rafael J. Wysocki Acked-by: Peter Zijlstra (Intel) --- drivers/cpuidle/cpuidle.c | 62 +++++++++++++++++------------------------------ include/linux/cpuidle.h | 17 +++++++++++-- kernel/sched/idle.c | 30 ++++++++++++++++------- 3 files changed, 58 insertions(+), 51 deletions(-) (limited to 'kernel') diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 8b3e132b6a01..080bd2dbde4b 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -44,8 +44,8 @@ void disable_cpuidle(void) off = 1; } -static bool cpuidle_not_available(struct cpuidle_driver *drv, - struct cpuidle_device *dev) +bool cpuidle_not_available(struct cpuidle_driver *drv, + struct cpuidle_device *dev) { return off || !initialized || !drv || !dev || !dev->enabled; } @@ -72,14 +72,8 @@ int cpuidle_play_dead(void) return -ENODEV; } -/** - * cpuidle_find_deepest_state - Find deepest state meeting specific conditions. - * @drv: cpuidle driver for the given CPU. - * @dev: cpuidle device for the given CPU. - * @freeze: Whether or not the state should be suitable for suspend-to-idle. - */ -static int cpuidle_find_deepest_state(struct cpuidle_driver *drv, - struct cpuidle_device *dev, bool freeze) +static int find_deepest_state(struct cpuidle_driver *drv, + struct cpuidle_device *dev, bool freeze) { unsigned int latency_req = 0; int i, ret = freeze ? -1 : CPUIDLE_DRIVER_STATE_START - 1; @@ -98,6 +92,17 @@ static int cpuidle_find_deepest_state(struct cpuidle_driver *drv, return ret; } +/** + * cpuidle_find_deepest_state - Find the deepest available idle state. + * @drv: cpuidle driver for the given CPU. + * @dev: cpuidle device for the given CPU. + */ +int cpuidle_find_deepest_state(struct cpuidle_driver *drv, + struct cpuidle_device *dev) +{ + return find_deepest_state(drv, dev, false); +} + static void enter_freeze_proper(struct cpuidle_driver *drv, struct cpuidle_device *dev, int index) { @@ -119,46 +124,26 @@ static void enter_freeze_proper(struct cpuidle_driver *drv, /** * cpuidle_enter_freeze - Enter an idle state suitable for suspend-to-idle. + * @drv: cpuidle driver for the given CPU. + * @dev: cpuidle device for the given CPU. * * If there are states with the ->enter_freeze callback, find the deepest of - * them and enter it with frozen tick. Otherwise, find the deepest state - * available and enter it normally. - * - * Returns with enabled interrupts. + * them and enter it with frozen tick. */ -void cpuidle_enter_freeze(void) +int cpuidle_enter_freeze(struct cpuidle_driver *drv, struct cpuidle_device *dev) { - struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices); - struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); int index; - if (cpuidle_not_available(drv, dev)) - goto fallback; - /* * Find the deepest state with ->enter_freeze present, which guarantees * that interrupts won't be enabled when it exits and allows the tick to * be frozen safely. */ - index = cpuidle_find_deepest_state(drv, dev, true); - if (index >= 0) { + index = find_deepest_state(drv, dev, true); + if (index >= 0) enter_freeze_proper(drv, dev, index); - local_irq_enable(); - return; - } - /* - * It is not safe to freeze the tick, find the deepest state available - * at all and try to enter it normally. - */ - index = cpuidle_find_deepest_state(drv, dev, false); - if (index >= 0) { - cpuidle_enter(drv, dev, index); - return; - } - - fallback: - arch_cpu_idle(); + return index; } /** @@ -217,9 +202,6 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, */ int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) { - if (cpuidle_not_available(drv, dev)) - return -ENODEV; - return cpuidle_curr_governor->select(drv, dev); } diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h index f551a9299ac9..306178d7309f 100644 --- a/include/linux/cpuidle.h +++ b/include/linux/cpuidle.h @@ -126,6 +126,8 @@ struct cpuidle_driver { #ifdef CONFIG_CPU_IDLE extern void disable_cpuidle(void); +extern bool cpuidle_not_available(struct cpuidle_driver *drv, + struct cpuidle_device *dev); extern int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev); @@ -150,11 +152,17 @@ extern void cpuidle_resume(void); extern int cpuidle_enable_device(struct cpuidle_device *dev); extern void cpuidle_disable_device(struct cpuidle_device *dev); extern int cpuidle_play_dead(void); -extern void cpuidle_enter_freeze(void); +extern int cpuidle_find_deepest_state(struct cpuidle_driver *drv, + struct cpuidle_device *dev); +extern int cpuidle_enter_freeze(struct cpuidle_driver *drv, + struct cpuidle_device *dev); extern struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev); #else static inline void disable_cpuidle(void) { } +static inline bool cpuidle_not_available(struct cpuidle_driver *drv, + struct cpuidle_device *dev) +{return true; } static inline int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) {return -ENODEV; } @@ -183,7 +191,12 @@ static inline int cpuidle_enable_device(struct cpuidle_device *dev) {return -ENODEV; } static inline void cpuidle_disable_device(struct cpuidle_device *dev) { } static inline int cpuidle_play_dead(void) {return -ENODEV; } -static inline void cpuidle_enter_freeze(void) { } +static inline int cpuidle_find_deepest_state(struct cpuidle_driver *drv, + struct cpuidle_device *dev) +{return -ENODEV; } +static inline int cpuidle_enter_freeze(struct cpuidle_driver *drv, + struct cpuidle_device *dev) +{return -ENODEV; } static inline struct cpuidle_driver *cpuidle_get_cpu_driver( struct cpuidle_device *dev) {return NULL; } #endif diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 84b93b68482a..80014a178342 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -82,6 +82,7 @@ static void cpuidle_idle_call(void) struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); int next_state, entered_state; unsigned int broadcast; + bool reflect; /* * Check if the idle task must be rescheduled. If it is the @@ -105,6 +106,9 @@ static void cpuidle_idle_call(void) */ rcu_idle_enter(); + if (cpuidle_not_available(drv, dev)) + goto use_default; + /* * Suspend-to-idle ("freeze") is a system state in which all user space * has been frozen, all I/O devices have been suspended and the only @@ -115,15 +119,22 @@ static void cpuidle_idle_call(void) * until a proper wakeup interrupt happens. */ if (idle_should_freeze()) { - cpuidle_enter_freeze(); - goto exit_idle; - } + entered_state = cpuidle_enter_freeze(drv, dev); + if (entered_state >= 0) { + local_irq_enable(); + goto exit_idle; + } - /* - * Ask the cpuidle framework to choose a convenient idle state. - * Fall back to the default arch idle method on errors. - */ - next_state = cpuidle_select(drv, dev); + reflect = false; + next_state = cpuidle_find_deepest_state(drv, dev); + } else { + reflect = true; + /* + * Ask the cpuidle framework to choose a convenient idle state. + */ + next_state = cpuidle_select(drv, dev); + } + /* Fall back to the default arch idle method on errors. */ if (next_state < 0) goto use_default; @@ -170,7 +181,8 @@ static void cpuidle_idle_call(void) /* * Give the governor an opportunity to reflect on the outcome */ - cpuidle_reflect(dev, entered_state); + if (reflect) + cpuidle_reflect(dev, entered_state); exit_idle: __current_set_polling(); -- cgit v1.2.3-59-g8ed1b