[PATCH] cpuidle: Handle tick_broadcast_enter() failure gracefully

From: Preeti U Murthy
Date: Thu May 07 2015 - 01:26:44 EST

When a CPU has to enter an idle state where tick stops, it makes a call
to tick_broadcast_enter(). The call will fail if this CPU is the
broadcast CPU. Today, under such a circumstance, the arch cpuidle code
handles this CPU. This is not convincing because not only are we not
aware what the arch cpuidle code does, but we also do not account for
the idle state residency time and usage of such a CPU.

This scenario can be handled better by simply asking the cpuidle
governor to choose an idle state where in ticks do not stop. To
accommodate this change move the setting of runqueue idle state from the
core to the cpuidle driver, else the rq->idle_state will be set wrong.

Signed-off-by: Preeti U Murthy <preeti@xxxxxxxxxxxxxxxxxx>
---
Based on linux-pm/bleeding-edge

drivers/cpuidle/cpuidle.c | 21 +++++++++++++++++----
drivers/cpuidle/governors/ladder.c | 13 ++++++++++---
drivers/cpuidle/governors/menu.c | 6 +++++-
include/linux/cpuidle.h | 6 +++---
include/linux/sched.h | 16 ++++++++++++++++
kernel/sched/core.c | 17 +++++++++++++++++
kernel/sched/fair.c | 2 +-
kernel/sched/idle.c | 8 +-------
kernel/sched/sched.h | 24 ------------------------
9 files changed, 70 insertions(+), 43 deletions(-)

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 61c417b..8f5657e 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -21,6 +21,7 @@
#include <linux/module.h>
#include <linux/suspend.h>
#include <linux/tick.h>
+#include <linux/sched.h>
#include <trace/events/power.h>

#include "cpuidle.h"
@@ -167,8 +168,15 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
* local timer will be shut down. If a local timer is used from another
* CPU as a broadcast timer, this call may fail if it is not available.
*/
- if (broadcast && tick_broadcast_enter())
- return -EBUSY;
+ if (broadcast && tick_broadcast_enter()) {
+ index = cpuidle_select(drv, dev, !broadcast);
+ if (index < 0)
+ return -EBUSY;
+ target_state = &drv->states[index];
+ }
+
+ /* Take note of the planned idle state. */
+ idle_set_state(smp_processor_id(), target_state);

trace_cpu_idle_rcuidle(index, dev->cpu);
time_start = ktime_get();
@@ -178,6 +186,9 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
time_end = ktime_get();
trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);

+ /* The cpu is no longer idle or about to enter idle. */
+ idle_set_state(smp_processor_id(), NULL);
+
if (broadcast) {
if (WARN_ON_ONCE(!irqs_disabled()))
local_irq_disable();
@@ -213,12 +224,14 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
*
* @drv: the cpuidle driver
* @dev: the cpuidle device
+ * @timer_stop_valid: allow selection of idle state where tick stops
*
* Returns the index of the idle state.
*/
-int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
+int cpuidle_select(struct cpuidle_driver *drv,
+ struct cpuidle_device *dev, int timer_stop_valid)
{
- return cpuidle_curr_governor->select(drv, dev);
+ return cpuidle_curr_governor->select(drv, dev, timer_stop_valid);
}

/**
diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c
index 401c010..c437322 100644
--- a/drivers/cpuidle/governors/ladder.c
+++ b/drivers/cpuidle/governors/ladder.c
@@ -62,9 +62,10 @@ static inline void ladder_do_selection(struct ladder_device *ldev,
* ladder_select_state - selects the next state to enter
* @drv: cpuidle driver
* @dev: the CPU
+ * @timer_stop_valid: allow selection of idle state where tick stops
*/
static int ladder_select_state(struct cpuidle_driver *drv,
- struct cpuidle_device *dev)
+ struct cpuidle_device *dev, int timer_stop_valid)
{
struct ladder_device *ldev = this_cpu_ptr(&ladder_devices);
struct ladder_device_state *last_state;
@@ -86,6 +87,7 @@ static int ladder_select_state(struct cpuidle_driver *drv,
!drv->states[last_idx + 1].disabled &&
!dev->states_usage[last_idx + 1].disable &&
last_residency > last_state->threshold.promotion_time &&
+ !(!timer_stop_valid && (drv->states[last_idx + 1].flags & CPUIDLE_FLAG_TIMER_STOP)) &&
drv->states[last_idx + 1].exit_latency <= latency_req) {
last_state->stats.promotion_count++;
last_state->stats.demotion_count = 0;
@@ -99,11 +101,14 @@ static int ladder_select_state(struct cpuidle_driver *drv,
if (last_idx > CPUIDLE_DRIVER_STATE_START &&
(drv->states[last_idx].disabled ||
dev->states_usage[last_idx].disable ||
+ (!timer_stop_valid && (drv->states[last_idx].flags & CPUIDLE_FLAG_TIMER_STOP)) ||
drv->states[last_idx].exit_latency > latency_req)) {
int i;

for (i = last_idx - 1; i > CPUIDLE_DRIVER_STATE_START; i--) {
- if (drv->states[i].exit_latency <= latency_req)
+ if (drv->states[i].exit_latency <= latency_req &&
+ !(!timer_stop_valid &&
+ (drv->states[i].flags & CPUIDLE_FLAG_TIMER_STOP)))
break;
}
ladder_do_selection(ldev, last_idx, i);
@@ -114,7 +119,9 @@ static int ladder_select_state(struct cpuidle_driver *drv,
last_residency < last_state->threshold.demotion_time) {
last_state->stats.demotion_count++;
last_state->stats.promotion_count = 0;
- if (last_state->stats.demotion_count >= last_state->threshold.demotion_count) {
+ if (last_state->stats.demotion_count >= last_state->threshold.demotion_count &&
+ !(!timer_stop_valid &&
+ (drv->states[last_idx - 1].flags & CPUIDLE_FLAG_TIMER_STOP))) {
ladder_do_selection(ldev, last_idx, last_idx - 1);
return last_idx - 1;
}
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index b8a5fa1..900404f 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -280,8 +280,10 @@ again:
* menu_select - selects the next idle state to enter
* @drv: cpuidle driver containing state data
* @dev: the CPU
+ * @timer_stop_valid: allow selection of idle state where tick stops
*/
-static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
+static int menu_select(struct cpuidle_driver *drv,
+ struct cpuidle_device *dev, int timer_stop_valid)
{
struct menu_device *data = this_cpu_ptr(&menu_devices);
int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
@@ -349,6 +351,8 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
continue;
if (s->exit_latency > latency_req)
continue;
+ if (!timer_stop_valid && (s->flags & CPUIDLE_FLAG_TIMER_STOP))
+ continue;

data->last_state_idx = i;
}
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index 9c5e892..d7c1734 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -129,7 +129,7 @@ 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);
+ struct cpuidle_device *dev, int timer_stop_valid);
extern int cpuidle_enter(struct cpuidle_driver *drv,
struct cpuidle_device *dev, int index);
extern void cpuidle_reflect(struct cpuidle_device *dev, int index);
@@ -163,7 +163,7 @@ 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)
+ struct cpuidle_device *dev, int timer_stop_valid)
{return -ENODEV; }
static inline int cpuidle_enter(struct cpuidle_driver *drv,
struct cpuidle_device *dev, int index)
@@ -223,7 +223,7 @@ struct cpuidle_governor {
struct cpuidle_device *dev);

int (*select) (struct cpuidle_driver *drv,
- struct cpuidle_device *dev);
+ struct cpuidle_device *dev, int timer_stop_valid);
void (*reflect) (struct cpuidle_device *dev, int index);

struct module *owner;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8222ae4..ff4e2df 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -45,6 +45,7 @@ struct sched_param {
#include <linux/rcupdate.h>
#include <linux/rculist.h>
#include <linux/rtmutex.h>
+#include <linux/cpuidle.h>

#include <linux/time.h>
#include <linux/param.h>
@@ -901,6 +902,21 @@ enum cpu_idle_type {
CPU_MAX_IDLE_TYPES
};

+#ifdef CONFIG_CPU_IDLE
+extern void idle_set_state(int cpu, struct cpuidle_state *idle_state);
+extern struct cpuidle_state *idle_get_state(int cpu);
+#else
+static inline void idle_set_state(int cpu,
+ struct cpuidle_state *idle_state)
+{
+}
+
+static inline struct cpuidle_state *idle_get_state(int cpu)
+{
+ return NULL;
+}
+#endif
+
/*
* Increase resolution of cpu_capacity calculations
*/
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f9123a8..427e190 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3231,6 +3231,23 @@ struct task_struct *idle_task(int cpu)
return cpu_rq(cpu)->idle;
}

+#ifdef CONFIG_CPU_IDLE
+void idle_set_state(int cpu, struct cpuidle_state *idle_state)
+{
+ struct rq *rq = cpu_rq(cpu);
+
+ rq->idle_state = idle_state;
+}
+
+struct cpuidle_state *idle_get_state(int cpu)
+{
+ struct rq *rq = cpu_rq(cpu);
+
+ WARN_ON(!rcu_read_lock_held());
+ return rq->idle_state;
+}
+#endif /* CONFIG_CPU_IDLE */
+
/**
* find_process_by_pid - find a process with a matching PID value.
* @pid: the pid in question.
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ffeaa41..211ef9a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4709,7 +4709,7 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
if (idle_cpu(i)) {
struct rq *rq = cpu_rq(i);
- struct cpuidle_state *idle = idle_get_state(rq);
+ struct cpuidle_state *idle = idle_get_state(i);
if (idle && idle->exit_latency < min_exit_latency) {
/*
* We give priority to a CPU whose idle state
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index fefcb1f..5bd766c 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -131,7 +131,7 @@ static void cpuidle_idle_call(void)
/*
* Ask the cpuidle framework to choose a convenient idle state.
*/
- next_state = cpuidle_select(drv, dev);
+ next_state = cpuidle_select(drv, dev, 1);
}
/* Fall back to the default arch idle method on errors. */
if (next_state < 0)
@@ -149,9 +149,6 @@ static void cpuidle_idle_call(void)
goto exit_idle;
}

- /* Take note of the planned idle state. */
- idle_set_state(this_rq(), &drv->states[next_state]);
-
/*
* Enter the idle state previously returned by the governor decision.
* This function will block until an interrupt occurs and will take
@@ -159,9 +156,6 @@ static void cpuidle_idle_call(void)
*/
entered_state = cpuidle_enter(drv, dev, next_state);

- /* The cpu is no longer idle or about to enter idle. */
- idle_set_state(this_rq(), NULL);
-
if (entered_state == -EBUSY)
goto use_default;

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index e0e1299..2c56caa 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1253,30 +1253,6 @@ static inline void idle_exit_fair(struct rq *rq) { }

#endif

-#ifdef CONFIG_CPU_IDLE
-static inline void idle_set_state(struct rq *rq,
- struct cpuidle_state *idle_state)
-{
- rq->idle_state = idle_state;
-}
-
-static inline struct cpuidle_state *idle_get_state(struct rq *rq)
-{
- WARN_ON(!rcu_read_lock_held());
- return rq->idle_state;
-}
-#else
-static inline void idle_set_state(struct rq *rq,
- struct cpuidle_state *idle_state)
-{
-}
-
-static inline struct cpuidle_state *idle_get_state(struct rq *rq)
-{
- return NULL;
-}
-#endif
-
extern void sysrq_sched_debug_show(void);
extern void sched_init_granularity(void);
extern void update_max_interval(void);

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