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core_ctl.c
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core_ctl.c
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/* Copyright (c) 2014-2016, The Linux Foundation. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 and
* only version 2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <linux/init.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/cpumask.h>
#include <linux/cpufreq.h>
#include <linux/timer.h>
#include <linux/kthread.h>
#include <linux/sched.h>
#include <linux/sched/rt.h>
#include <linux/mutex.h>
#include <trace/events/sched.h>
#define MAX_CPUS_PER_GROUP 2
struct cpu_data {
/* Per CPU data. */
bool inited;
bool online;
bool rejected;
bool is_busy;
bool not_preferred;
unsigned int busy;
unsigned int cpu;
struct list_head sib;
unsigned int first_cpu;
struct list_head pending_sib;
/* Per cluster data set only on first CPU */
unsigned int min_cpus;
unsigned int max_cpus;
unsigned int offline_delay_ms;
unsigned int busy_up_thres[MAX_CPUS_PER_GROUP];
unsigned int busy_down_thres[MAX_CPUS_PER_GROUP];
unsigned int online_cpus;
unsigned int avail_cpus;
unsigned int num_cpus;
unsigned int need_cpus;
unsigned int task_thres;
s64 need_ts;
struct list_head lru;
bool pending;
spinlock_t pending_lock;
bool is_big_cluster;
int nrrun;
bool nrrun_changed;
struct timer_list timer;
struct task_struct *hotplug_thread;
struct kobject kobj;
struct list_head pending_lru;
bool disabled;
};
static DEFINE_PER_CPU(struct cpu_data, cpu_state);
static DEFINE_SPINLOCK(state_lock);
static DEFINE_SPINLOCK(pending_lru_lock);
static DEFINE_MUTEX(lru_lock);
static void apply_need(struct cpu_data *f);
static void wake_up_hotplug_thread(struct cpu_data *state);
static void add_to_pending_lru(struct cpu_data *state);
static void update_lru(struct cpu_data *state);
/* ========================= sysfs interface =========================== */
static ssize_t store_min_cpus(struct cpu_data *state,
const char *buf, size_t count)
{
unsigned int val;
if (sscanf(buf, "%u\n", &val) != 1)
return -EINVAL;
state->min_cpus = min(val, state->max_cpus);
wake_up_hotplug_thread(state);
return count;
}
static ssize_t show_min_cpus(struct cpu_data *state, char *buf)
{
return snprintf(buf, PAGE_SIZE, "%u\n", state->min_cpus);
}
static ssize_t store_max_cpus(struct cpu_data *state,
const char *buf, size_t count)
{
unsigned int val;
if (sscanf(buf, "%u\n", &val) != 1)
return -EINVAL;
val = min(val, state->num_cpus);
state->max_cpus = val;
state->min_cpus = min(state->min_cpus, state->max_cpus);
wake_up_hotplug_thread(state);
return count;
}
static ssize_t show_max_cpus(struct cpu_data *state, char *buf)
{
return snprintf(buf, PAGE_SIZE, "%u\n", state->max_cpus);
}
static ssize_t store_offline_delay_ms(struct cpu_data *state,
const char *buf, size_t count)
{
unsigned int val;
if (sscanf(buf, "%u\n", &val) != 1)
return -EINVAL;
state->offline_delay_ms = val;
apply_need(state);
return count;
}
static ssize_t show_task_thres(struct cpu_data *state, char *buf)
{
return snprintf(buf, PAGE_SIZE, "%u\n", state->task_thres);
}
static ssize_t store_task_thres(struct cpu_data *state,
const char *buf, size_t count)
{
unsigned int val;
if (sscanf(buf, "%u\n", &val) != 1)
return -EINVAL;
if (val < state->num_cpus)
return -EINVAL;
state->task_thres = val;
apply_need(state);
return count;
}
static ssize_t show_offline_delay_ms(struct cpu_data *state, char *buf)
{
return snprintf(buf, PAGE_SIZE, "%u\n", state->offline_delay_ms);
}
static ssize_t store_busy_up_thres(struct cpu_data *state,
const char *buf, size_t count)
{
unsigned int val[MAX_CPUS_PER_GROUP];
int ret, i;
ret = sscanf(buf, "%u %u %u %u\n", &val[0], &val[1], &val[2], &val[3]);
if (ret != 1 && ret != state->num_cpus)
return -EINVAL;
if (ret == 1) {
for (i = 0; i < state->num_cpus; i++)
state->busy_up_thres[i] = val[0];
} else {
for (i = 0; i < state->num_cpus; i++)
state->busy_up_thres[i] = val[i];
}
apply_need(state);
return count;
}
static ssize_t show_busy_up_thres(struct cpu_data *state, char *buf)
{
int i, count = 0;
for (i = 0; i < state->num_cpus; i++)
count += snprintf(buf + count, PAGE_SIZE - count, "%u ",
state->busy_up_thres[i]);
count += snprintf(buf + count, PAGE_SIZE - count, "\n");
return count;
}
static ssize_t store_busy_down_thres(struct cpu_data *state,
const char *buf, size_t count)
{
unsigned int val[MAX_CPUS_PER_GROUP];
int ret, i;
ret = sscanf(buf, "%u %u %u %u\n", &val[0], &val[1], &val[2], &val[3]);
if (ret != 1 && ret != state->num_cpus)
return -EINVAL;
if (ret == 1) {
for (i = 0; i < state->num_cpus; i++)
state->busy_down_thres[i] = val[0];
} else {
for (i = 0; i < state->num_cpus; i++)
state->busy_down_thres[i] = val[i];
}
apply_need(state);
return count;
}
static ssize_t show_busy_down_thres(struct cpu_data *state, char *buf)
{
int i, count = 0;
for (i = 0; i < state->num_cpus; i++)
count += snprintf(buf + count, PAGE_SIZE - count, "%u ",
state->busy_down_thres[i]);
count += snprintf(buf + count, PAGE_SIZE - count, "\n");
return count;
}
static ssize_t store_is_big_cluster(struct cpu_data *state,
const char *buf, size_t count)
{
unsigned int val;
if (sscanf(buf, "%u\n", &val) != 1)
return -EINVAL;
state->is_big_cluster = val ? 1 : 0;
return count;
}
static ssize_t show_is_big_cluster(struct cpu_data *state, char *buf)
{
return snprintf(buf, PAGE_SIZE, "%u\n", state->is_big_cluster);
}
static ssize_t show_cpus(struct cpu_data *state, char *buf)
{
struct cpu_data *c;
ssize_t count = 0;
unsigned long flags;
spin_lock_irqsave(&state_lock, flags);
list_for_each_entry(c, &state->lru, sib) {
count += snprintf(buf + count, PAGE_SIZE - count,
"CPU%u (%s)\n", c->cpu,
c->online ? "Online" : "Offline");
}
spin_unlock_irqrestore(&state_lock, flags);
return count;
}
static ssize_t show_need_cpus(struct cpu_data *state, char *buf)
{
return snprintf(buf, PAGE_SIZE, "%u\n", state->need_cpus);
}
static ssize_t show_online_cpus(struct cpu_data *state, char *buf)
{
return snprintf(buf, PAGE_SIZE, "%u\n", state->online_cpus);
}
static ssize_t show_global_state(struct cpu_data *state, char *buf)
{
struct cpu_data *c;
ssize_t count = 0;
unsigned int cpu;
for_each_possible_cpu(cpu) {
count += snprintf(buf + count, PAGE_SIZE - count,
"CPU%u\n", cpu);
c = &per_cpu(cpu_state, cpu);
if (!c->inited)
continue;
count += snprintf(buf + count, PAGE_SIZE - count,
"\tCPU: %u\n", c->cpu);
count += snprintf(buf + count, PAGE_SIZE - count,
"\tOnline: %u\n", c->online);
count += snprintf(buf + count, PAGE_SIZE - count,
"\tRejected: %u\n", c->rejected);
count += snprintf(buf + count, PAGE_SIZE - count,
"\tFirst CPU: %u\n", c->first_cpu);
count += snprintf(buf + count, PAGE_SIZE - count,
"\tBusy%%: %u\n", c->busy);
count += snprintf(buf + count, PAGE_SIZE - count,
"\tIs busy: %u\n", c->is_busy);
if (c->cpu != c->first_cpu)
continue;
count += snprintf(buf + count, PAGE_SIZE - count,
"\tNr running: %u\n", c->nrrun);
count += snprintf(buf + count, PAGE_SIZE - count,
"\tAvail CPUs: %u\n", c->avail_cpus);
count += snprintf(buf + count, PAGE_SIZE - count,
"\tNeed CPUs: %u\n", c->need_cpus);
count += snprintf(buf + count, PAGE_SIZE - count,
"\tStatus: %s\n",
c->disabled ? "disabled" : "enabled");
}
return count;
}
static ssize_t store_not_preferred(struct cpu_data *state,
const char *buf, size_t count)
{
struct cpu_data *c;
unsigned int i, first_cpu;
unsigned int val[MAX_CPUS_PER_GROUP];
int ret;
ret = sscanf(buf, "%u %u %u %u\n", &val[0], &val[1], &val[2], &val[3]);
if (ret != 1 && ret != state->num_cpus)
return -EINVAL;
first_cpu = state->first_cpu;
for (i = 0; i < state->num_cpus; i++) {
c = &per_cpu(cpu_state, first_cpu);
c->not_preferred = val[i];
first_cpu++;
}
return count;
}
static ssize_t show_not_preferred(struct cpu_data *state, char *buf)
{
struct cpu_data *c;
ssize_t count = 0;
unsigned int i, first_cpu;
first_cpu = state->first_cpu;
for (i = 0; i < state->num_cpus; i++) {
c = &per_cpu(cpu_state, first_cpu);
count += snprintf(buf + count, PAGE_SIZE - count,
"\tCPU:%d %u\n", first_cpu, c->not_preferred);
first_cpu++;
}
return count;
}
static ssize_t store_disable(struct cpu_data *state,
const char *buf, size_t count)
{
unsigned int val;
if (sscanf(buf, "%u\n", &val) != 1)
return -EINVAL;
val = !!val;
if (state->disabled == val)
return count;
state->disabled = val;
if (!state->disabled)
wake_up_hotplug_thread(state);
return count;
}
static ssize_t show_disable(struct cpu_data *state, char *buf)
{
return snprintf(buf, PAGE_SIZE, "%u\n", state->disabled);
}
struct core_ctl_attr {
struct attribute attr;
ssize_t (*show)(struct cpu_data *, char *);
ssize_t (*store)(struct cpu_data *, const char *, size_t count);
};
#define core_ctl_attr_ro(_name) \
static struct core_ctl_attr _name = \
__ATTR(_name, 0444, show_##_name, NULL)
#define core_ctl_attr_rw(_name) \
static struct core_ctl_attr _name = \
__ATTR(_name, 0644, show_##_name, store_##_name)
core_ctl_attr_rw(min_cpus);
core_ctl_attr_rw(max_cpus);
core_ctl_attr_rw(offline_delay_ms);
core_ctl_attr_rw(busy_up_thres);
core_ctl_attr_rw(busy_down_thres);
core_ctl_attr_rw(task_thres);
core_ctl_attr_rw(is_big_cluster);
core_ctl_attr_ro(cpus);
core_ctl_attr_ro(need_cpus);
core_ctl_attr_ro(online_cpus);
core_ctl_attr_ro(global_state);
core_ctl_attr_rw(not_preferred);
core_ctl_attr_rw(disable);
static struct attribute *default_attrs[] = {
&min_cpus.attr,
&max_cpus.attr,
&offline_delay_ms.attr,
&busy_up_thres.attr,
&busy_down_thres.attr,
&task_thres.attr,
&is_big_cluster.attr,
&cpus.attr,
&need_cpus.attr,
&online_cpus.attr,
&global_state.attr,
¬_preferred.attr,
&disable.attr,
NULL
};
#define to_cpu_data(k) container_of(k, struct cpu_data, kobj)
#define to_attr(a) container_of(a, struct core_ctl_attr, attr)
static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf)
{
struct cpu_data *data = to_cpu_data(kobj);
struct core_ctl_attr *cattr = to_attr(attr);
ssize_t ret = -EIO;
if (cattr->show)
ret = cattr->show(data, buf);
return ret;
}
static ssize_t store(struct kobject *kobj, struct attribute *attr,
const char *buf, size_t count)
{
struct cpu_data *data = to_cpu_data(kobj);
struct core_ctl_attr *cattr = to_attr(attr);
ssize_t ret = -EIO;
if (cattr->store)
ret = cattr->store(data, buf, count);
return ret;
}
static const struct sysfs_ops sysfs_ops = {
.show = show,
.store = store,
};
static struct kobj_type ktype_core_ctl = {
.sysfs_ops = &sysfs_ops,
.default_attrs = default_attrs,
};
/* ==================== runqueue based core count =================== */
#define RQ_AVG_TOLERANCE 2
#define RQ_AVG_DEFAULT_MS 20
#define NR_RUNNING_TOLERANCE 5
static unsigned int rq_avg_period_ms = RQ_AVG_DEFAULT_MS;
static s64 rq_avg_timestamp_ms;
static struct timer_list rq_avg_timer;
static void update_running_avg(bool trigger_update)
{
int cpu;
struct cpu_data *pcpu;
int avg, iowait_avg, big_avg, old_nrrun;
s64 now;
unsigned long flags;
spin_lock_irqsave(&state_lock, flags);
now = ktime_to_ms(ktime_get());
if (now - rq_avg_timestamp_ms < rq_avg_period_ms - RQ_AVG_TOLERANCE) {
spin_unlock_irqrestore(&state_lock, flags);
return;
}
rq_avg_timestamp_ms = now;
sched_get_nr_running_avg(&avg, &iowait_avg, &big_avg);
spin_unlock_irqrestore(&state_lock, flags);
/*
* Round up to the next integer if the average nr running tasks
* is within NR_RUNNING_TOLERANCE/100 of the next integer.
* If normal rounding up is used, it will allow a transient task
* to trigger online event. By the time core is onlined, the task
* has finished.
* Rounding to closest suffers same problem because scheduler
* might only provide running stats per jiffy, and a transient
* task could skew the number for one jiffy. If core control
* samples every 2 jiffies, it will observe 0.5 additional running
* average which rounds up to 1 task.
*/
avg = (avg + NR_RUNNING_TOLERANCE) / 100;
big_avg = (big_avg + NR_RUNNING_TOLERANCE) / 100;
for_each_possible_cpu(cpu) {
pcpu = &per_cpu(cpu_state, cpu);
if (!pcpu->inited || pcpu->first_cpu != cpu)
continue;
old_nrrun = pcpu->nrrun;
/*
* Big cluster only need to take care of big tasks, but if
* there are not enough big cores, big tasks need to be run
* on little as well. Thus for little's runqueue stat, it
* has to use overall runqueue average, or derive what big
* tasks would have to be run on little. The latter approach
* is not easy to get given core control reacts much slower
* than scheduler, and can't predict scheduler's behavior.
*/
pcpu->nrrun = pcpu->is_big_cluster ? big_avg : avg;
if (pcpu->nrrun != old_nrrun) {
if (trigger_update)
apply_need(pcpu);
else
pcpu->nrrun_changed = true;
}
}
}
/* adjust needed CPUs based on current runqueue information */
static unsigned int apply_task_need(struct cpu_data *f, unsigned int new_need)
{
/* Online all cores if there are enough tasks */
if (f->nrrun >= f->task_thres)
return f->num_cpus;
/* only online more cores if there are tasks to run */
if (f->nrrun > new_need)
return new_need + 1;
return new_need;
}
static u64 round_to_nw_start(void)
{
unsigned long step = msecs_to_jiffies(rq_avg_period_ms);
u64 jif = get_jiffies_64();
do_div(jif, step);
return (jif + 1) * step;
}
static void rq_avg_timer_func(unsigned long not_used)
{
update_running_avg(true);
mod_timer(&rq_avg_timer, round_to_nw_start());
}
/* ======================= load based core count ====================== */
static unsigned int apply_limits(struct cpu_data *f, unsigned int need_cpus)
{
return min(max(f->min_cpus, need_cpus), f->max_cpus);
}
static bool eval_need(struct cpu_data *f)
{
unsigned long flags;
struct cpu_data *c;
unsigned int need_cpus = 0, last_need, thres_idx;
int ret = 0;
bool need_flag = false;
s64 now;
if (unlikely(!f->inited))
return 0;
spin_lock_irqsave(&state_lock, flags);
thres_idx = f->online_cpus ? f->online_cpus - 1 : 0;
list_for_each_entry(c, &f->lru, sib) {
if (c->busy >= f->busy_up_thres[thres_idx])
c->is_busy = true;
else if (c->busy < f->busy_down_thres[thres_idx])
c->is_busy = false;
need_cpus += c->is_busy;
}
need_cpus = apply_task_need(f, need_cpus);
need_flag = apply_limits(f, need_cpus) != apply_limits(f, f->need_cpus);
last_need = f->need_cpus;
now = ktime_to_ms(ktime_get());
if (need_cpus == last_need) {
f->need_ts = now;
spin_unlock_irqrestore(&state_lock, flags);
return 0;
}
if (need_cpus > last_need) {
ret = 1;
} else if (need_cpus < last_need) {
s64 elapsed = now - f->need_ts;
if (elapsed >= f->offline_delay_ms) {
ret = 1;
} else {
mod_timer(&f->timer, jiffies +
msecs_to_jiffies(f->offline_delay_ms));
}
}
if (ret) {
f->need_ts = now;
f->need_cpus = need_cpus;
}
trace_core_ctl_eval_need(f->cpu, last_need, need_cpus,
ret && need_flag);
spin_unlock_irqrestore(&state_lock, flags);
return ret && need_flag;
}
static void apply_need(struct cpu_data *f)
{
if (eval_need(f))
wake_up_hotplug_thread(f);
}
static int core_ctl_set_busy(unsigned int cpu, unsigned int busy)
{
struct cpu_data *c = &per_cpu(cpu_state, cpu);
struct cpu_data *f;
unsigned int old_is_busy = c->is_busy;
if (!c->inited)
return 0;
f = &per_cpu(cpu_state, c->first_cpu);
update_running_avg(false);
if (c->busy == busy && !f->nrrun_changed)
return 0;
c->busy = busy;
f->nrrun_changed = false;
apply_need(f);
trace_core_ctl_set_busy(cpu, busy, old_is_busy, c->is_busy);
return 0;
}
/* ========================= core count enforcement ==================== */
/*
* If current thread is hotplug thread, don't attempt to wake up
* itself or other hotplug threads because it will deadlock. Instead,
* schedule a timer to fire in next timer tick and wake up the thread.
*/
static void wake_up_hotplug_thread(struct cpu_data *state)
{
unsigned long flags;
int cpu;
struct cpu_data *pcpu;
bool no_wakeup = false;
if (unlikely(state->disabled))
return;
for_each_possible_cpu(cpu) {
pcpu = &per_cpu(cpu_state, cpu);
if (cpu != pcpu->first_cpu)
continue;
if (pcpu->hotplug_thread == current) {
no_wakeup = true;
break;
}
}
spin_lock_irqsave(&state->pending_lock, flags);
state->pending = true;
spin_unlock_irqrestore(&state->pending_lock, flags);
if (no_wakeup) {
spin_lock_irqsave(&state_lock, flags);
mod_timer(&state->timer, jiffies);
spin_unlock_irqrestore(&state_lock, flags);
} else {
wake_up_process(state->hotplug_thread);
}
}
static void core_ctl_timer_func(unsigned long cpu)
{
struct cpu_data *state = &per_cpu(cpu_state, cpu);
unsigned long flags;
if (eval_need(state) && !state->disabled) {
spin_lock_irqsave(&state->pending_lock, flags);
state->pending = true;
spin_unlock_irqrestore(&state->pending_lock, flags);
wake_up_process(state->hotplug_thread);
}
}
static int core_ctl_online_core(unsigned int cpu)
{
int ret;
struct device *dev;
lock_device_hotplug();
dev = get_cpu_device(cpu);
if (!dev) {
pr_err("%s: failed to get cpu%d device\n", __func__, cpu);
ret = -ENODEV;
} else {
ret = device_online(dev);
}
unlock_device_hotplug();
return ret;
}
static int core_ctl_offline_core(unsigned int cpu)
{
int ret;
struct device *dev;
lock_device_hotplug();
dev = get_cpu_device(cpu);
if (!dev) {
pr_err("%s: failed to get cpu%d device\n", __func__, cpu);
ret = -ENODEV;
} else {
ret = device_offline(dev);
}
unlock_device_hotplug();
return ret;
}
static void update_lru(struct cpu_data *f)
{
struct cpu_data *c, *tmp;
unsigned long flags;
spin_lock_irqsave(&pending_lru_lock, flags);
spin_lock(&state_lock);
list_for_each_entry_safe(c, tmp, &f->pending_lru, pending_sib) {
list_del_init(&c->pending_sib);
list_del(&c->sib);
list_add_tail(&c->sib, &f->lru);
}
spin_unlock(&state_lock);
spin_unlock_irqrestore(&pending_lru_lock, flags);
}
static void __ref do_hotplug(struct cpu_data *f)
{
unsigned int need;
struct cpu_data *c, *tmp;
need = apply_limits(f, f->need_cpus);
pr_debug("Trying to adjust group %u to %u\n", f->first_cpu, need);
mutex_lock(&lru_lock);
if (f->online_cpus > need) {
list_for_each_entry_safe(c, tmp, &f->lru, sib) {
if (!c->online)
continue;
if (f->online_cpus == need)
break;
/* Don't offline busy CPUs. */
if (c->is_busy)
continue;
pr_debug("Trying to Offline CPU%u\n", c->cpu);
if (core_ctl_offline_core(c->cpu))
pr_debug("Unable to Offline CPU%u\n", c->cpu);
}
/*
* If the number of online CPUs is within the limits, then
* don't force any busy CPUs offline.
*/
if (f->online_cpus <= f->max_cpus)
goto done;
list_for_each_entry_safe(c, tmp, &f->lru, sib) {
if (!c->online)
continue;
if (f->online_cpus <= f->max_cpus)
break;
pr_debug("Trying to Offline CPU%u\n", c->cpu);
if (core_ctl_offline_core(c->cpu))
pr_debug("Unable to Offline CPU%u\n", c->cpu);
}
} else if (f->online_cpus < need) {
list_for_each_entry_safe(c, tmp, &f->lru, sib) {
if (c->online || c->rejected || c->not_preferred)
continue;
if (f->online_cpus == need)
break;
pr_debug("Trying to Online CPU%u\n", c->cpu);
if (core_ctl_online_core(c->cpu))
pr_debug("Unable to Online CPU%u\n", c->cpu);
}
if (f->online_cpus == need)
goto done;
list_for_each_entry_safe(c, tmp, &f->lru, sib) {
if (c->online || c->rejected || !c->not_preferred)
continue;
if (f->online_cpus == need)
break;
pr_debug("Trying to Online CPU%u\n", c->cpu);
if (core_ctl_online_core(c->cpu))
pr_debug("Unable to Online CPU%u\n", c->cpu);
}
}
done:
mutex_unlock(&lru_lock);
update_lru(f);
}
static int __ref try_hotplug(void *data)
{
struct cpu_data *f = data;
unsigned long flags;
while (1) {
set_current_state(TASK_INTERRUPTIBLE);
spin_lock_irqsave(&f->pending_lock, flags);
if (!f->pending) {
spin_unlock_irqrestore(&f->pending_lock, flags);
schedule();
if (kthread_should_stop())
break;
spin_lock_irqsave(&f->pending_lock, flags);
}
set_current_state(TASK_RUNNING);
f->pending = false;
spin_unlock_irqrestore(&f->pending_lock, flags);
do_hotplug(f);
}
return 0;
}
static void add_to_pending_lru(struct cpu_data *state)
{
unsigned long flags;
struct cpu_data *f = &per_cpu(cpu_state, state->first_cpu);
spin_lock_irqsave(&pending_lru_lock, flags);
if (!list_empty(&state->pending_sib))
list_del(&state->pending_sib);
list_add_tail(&state->pending_sib, &f->pending_lru);
spin_unlock_irqrestore(&pending_lru_lock, flags);
}
static int __ref cpu_callback(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
uint32_t cpu = (uintptr_t)hcpu;
struct cpu_data *state = &per_cpu(cpu_state, cpu);
struct cpu_data *f;
int ret = NOTIFY_OK;
unsigned long flags;
/* Don't affect suspend resume */
if (action & CPU_TASKS_FROZEN)
return NOTIFY_OK;
if (unlikely(!state->inited))
return NOTIFY_OK;
f = &per_cpu(cpu_state, state->first_cpu);
switch (action) {
case CPU_UP_PREPARE:
/* If online state of CPU somehow got out of sync, fix it. */
if (state->online) {
f->online_cpus--;
state->online = false;
pr_warn("CPU%d offline when state is online\n", cpu);
}
if (state->rejected) {
state->rejected = false;
f->avail_cpus++;
}
/*
* If a CPU is in the process of coming up, mark it as online
* so that there's no race with hotplug thread bringing up more
* CPUs than necessary.
*/
if (!f->disabled &&
apply_limits(f, f->need_cpus) <= f->online_cpus) {
pr_debug("Prevent CPU%d onlining\n", cpu);
ret = NOTIFY_BAD;
} else {
state->online = true;
f->online_cpus++;
}
break;
case CPU_ONLINE:
/*
* Moving to the end of the list should only happen in
* CPU_ONLINE and not on CPU_UP_PREPARE to prevent an
* infinite list traversal when thermal (or other entities)
* reject trying to online CPUs.
*/
ret = mutex_trylock(&lru_lock);
if (ret) {
spin_lock_irqsave(&state_lock, flags);
list_del(&state->sib);
list_add_tail(&state->sib, &f->lru);
spin_unlock_irqrestore(&state_lock, flags);
mutex_unlock(&lru_lock);
} else {
/*
* lru_lock is held by our hotplug thread to
* prevent concurrent access of lru list. The updates
* are maintained in pending_lru list and lru is
* updated at the end of do_hotplug().
*/
add_to_pending_lru(state);
}
break;
case CPU_DEAD:
/* Move a CPU to the end of the LRU when it goes offline. */
ret = mutex_trylock(&lru_lock);
if (ret) {
spin_lock_irqsave(&state_lock, flags);
list_del(&state->sib);
list_add_tail(&state->sib, &f->lru);
spin_unlock_irqrestore(&state_lock, flags);
mutex_unlock(&lru_lock);
} else {
add_to_pending_lru(state);
}
/* Fall through */
case CPU_UP_CANCELED:
/* If online state of CPU somehow got out of sync, fix it. */
if (!state->online) {
f->online_cpus++;
pr_warn("CPU%d online when state is offline\n", cpu);
}
if (!state->rejected && action == CPU_UP_CANCELED) {
state->rejected = true;
f->avail_cpus--;
}
state->online = false;
state->busy = 0;
f->online_cpus--;
break;
}
if (f->online_cpus < apply_limits(f, f->need_cpus)
&& f->online_cpus < f->avail_cpus
&& action == CPU_DEAD)
wake_up_hotplug_thread(f);
return ret;
}
static struct notifier_block __refdata cpu_notifier = {
.notifier_call = cpu_callback,
};
/* ============================ init code ============================== */
static int group_init(struct cpumask *mask)
{
struct device *dev;
unsigned int first_cpu = cpumask_first(mask);
struct cpu_data *f = &per_cpu(cpu_state, first_cpu);
struct cpu_data *state;
unsigned int cpu;
struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
if (likely(f->inited))
return 0;
dev = get_cpu_device(first_cpu);
if (!dev)