linux/kernel/sched/idle.c
Frederic Weisbecker e67198cc05 context_tracking: Take idle eqs entrypoints over RCU
The RCU dynticks counter is going to be merged into the context tracking
subsystem. Start with moving the idle extended quiescent states
entrypoints to context tracking. For now those are dumb redirections to
existing RCU calls.

[ paulmck: Apply kernel test robot feedback. ]

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao <liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
2022-07-05 13:32:16 -07:00

524 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Generic entry points for the idle threads and
* implementation of the idle task scheduling class.
*
* (NOTE: these are not related to SCHED_IDLE batch scheduled
* tasks which are handled in sched/fair.c )
*/
/* Linker adds these: start and end of __cpuidle functions */
extern char __cpuidle_text_start[], __cpuidle_text_end[];
/**
* sched_idle_set_state - Record idle state for the current CPU.
* @idle_state: State to record.
*/
void sched_idle_set_state(struct cpuidle_state *idle_state)
{
idle_set_state(this_rq(), idle_state);
}
static int __read_mostly cpu_idle_force_poll;
void cpu_idle_poll_ctrl(bool enable)
{
if (enable) {
cpu_idle_force_poll++;
} else {
cpu_idle_force_poll--;
WARN_ON_ONCE(cpu_idle_force_poll < 0);
}
}
#ifdef CONFIG_GENERIC_IDLE_POLL_SETUP
static int __init cpu_idle_poll_setup(char *__unused)
{
cpu_idle_force_poll = 1;
return 1;
}
__setup("nohlt", cpu_idle_poll_setup);
static int __init cpu_idle_nopoll_setup(char *__unused)
{
cpu_idle_force_poll = 0;
return 1;
}
__setup("hlt", cpu_idle_nopoll_setup);
#endif
static noinline int __cpuidle cpu_idle_poll(void)
{
trace_cpu_idle(0, smp_processor_id());
stop_critical_timings();
ct_idle_enter();
local_irq_enable();
while (!tif_need_resched() &&
(cpu_idle_force_poll || tick_check_broadcast_expired()))
cpu_relax();
ct_idle_exit();
start_critical_timings();
trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
return 1;
}
/* Weak implementations for optional arch specific functions */
void __weak arch_cpu_idle_prepare(void) { }
void __weak arch_cpu_idle_enter(void) { }
void __weak arch_cpu_idle_exit(void) { }
void __weak arch_cpu_idle_dead(void) { }
void __weak arch_cpu_idle(void)
{
cpu_idle_force_poll = 1;
raw_local_irq_enable();
}
/**
* default_idle_call - Default CPU idle routine.
*
* To use when the cpuidle framework cannot be used.
*/
void __cpuidle default_idle_call(void)
{
if (current_clr_polling_and_test()) {
local_irq_enable();
} else {
trace_cpu_idle(1, smp_processor_id());
stop_critical_timings();
/*
* arch_cpu_idle() is supposed to enable IRQs, however
* we can't do that because of RCU and tracing.
*
* Trace IRQs enable here, then switch off RCU, and have
* arch_cpu_idle() use raw_local_irq_enable(). Note that
* ct_idle_enter() relies on lockdep IRQ state, so switch that
* last -- this is very similar to the entry code.
*/
trace_hardirqs_on_prepare();
lockdep_hardirqs_on_prepare();
ct_idle_enter();
lockdep_hardirqs_on(_THIS_IP_);
arch_cpu_idle();
/*
* OK, so IRQs are enabled here, but RCU needs them disabled to
* turn itself back on.. funny thing is that disabling IRQs
* will cause tracing, which needs RCU. Jump through hoops to
* make it 'work'.
*/
raw_local_irq_disable();
lockdep_hardirqs_off(_THIS_IP_);
ct_idle_exit();
lockdep_hardirqs_on(_THIS_IP_);
raw_local_irq_enable();
start_critical_timings();
trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
}
}
static int call_cpuidle_s2idle(struct cpuidle_driver *drv,
struct cpuidle_device *dev)
{
if (current_clr_polling_and_test())
return -EBUSY;
return cpuidle_enter_s2idle(drv, dev);
}
static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
int next_state)
{
/*
* The idle task must be scheduled, it is pointless to go to idle, just
* update no idle residency and return.
*/
if (current_clr_polling_and_test()) {
dev->last_residency_ns = 0;
local_irq_enable();
return -EBUSY;
}
/*
* Enter the idle state previously returned by the governor decision.
* This function will block until an interrupt occurs and will take
* care of re-enabling the local interrupts
*/
return cpuidle_enter(drv, dev, next_state);
}
/**
* cpuidle_idle_call - the main idle function
*
* NOTE: no locks or semaphores should be used here
*
* On architectures that support TIF_POLLING_NRFLAG, is called with polling
* set, and it returns with polling set. If it ever stops polling, it
* must clear the polling bit.
*/
static void cpuidle_idle_call(void)
{
struct cpuidle_device *dev = cpuidle_get_device();
struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
int next_state, entered_state;
/*
* Check if the idle task must be rescheduled. If it is the
* case, exit the function after re-enabling the local irq.
*/
if (need_resched()) {
local_irq_enable();
return;
}
/*
* The RCU framework needs to be told that we are entering an idle
* section, so no more rcu read side critical sections and one more
* step to the grace period
*/
if (cpuidle_not_available(drv, dev)) {
tick_nohz_idle_stop_tick();
default_idle_call();
goto exit_idle;
}
/*
* Suspend-to-idle ("s2idle") is a system state in which all user space
* has been frozen, all I/O devices have been suspended and the only
* activity happens here and in interrupts (if any). In that case bypass
* the cpuidle governor and go straight for the deepest idle state
* available. Possibly also suspend the local tick and the entire
* timekeeping to prevent timer interrupts from kicking us out of idle
* until a proper wakeup interrupt happens.
*/
if (idle_should_enter_s2idle() || dev->forced_idle_latency_limit_ns) {
u64 max_latency_ns;
if (idle_should_enter_s2idle()) {
entered_state = call_cpuidle_s2idle(drv, dev);
if (entered_state > 0)
goto exit_idle;
max_latency_ns = U64_MAX;
} else {
max_latency_ns = dev->forced_idle_latency_limit_ns;
}
tick_nohz_idle_stop_tick();
next_state = cpuidle_find_deepest_state(drv, dev, max_latency_ns);
call_cpuidle(drv, dev, next_state);
} else {
bool stop_tick = true;
/*
* Ask the cpuidle framework to choose a convenient idle state.
*/
next_state = cpuidle_select(drv, dev, &stop_tick);
if (stop_tick || tick_nohz_tick_stopped())
tick_nohz_idle_stop_tick();
else
tick_nohz_idle_retain_tick();
entered_state = call_cpuidle(drv, dev, next_state);
/*
* Give the governor an opportunity to reflect on the outcome
*/
cpuidle_reflect(dev, entered_state);
}
exit_idle:
__current_set_polling();
/*
* It is up to the idle functions to reenable local interrupts
*/
if (WARN_ON_ONCE(irqs_disabled()))
local_irq_enable();
}
/*
* Generic idle loop implementation
*
* Called with polling cleared.
*/
static void do_idle(void)
{
int cpu = smp_processor_id();
/*
* Check if we need to update blocked load
*/
nohz_run_idle_balance(cpu);
/*
* If the arch has a polling bit, we maintain an invariant:
*
* Our polling bit is clear if we're not scheduled (i.e. if rq->curr !=
* rq->idle). This means that, if rq->idle has the polling bit set,
* then setting need_resched is guaranteed to cause the CPU to
* reschedule.
*/
__current_set_polling();
tick_nohz_idle_enter();
while (!need_resched()) {
rmb();
local_irq_disable();
if (cpu_is_offline(cpu)) {
tick_nohz_idle_stop_tick();
cpuhp_report_idle_dead();
arch_cpu_idle_dead();
}
arch_cpu_idle_enter();
rcu_nocb_flush_deferred_wakeup();
/*
* In poll mode we reenable interrupts and spin. Also if we
* detected in the wakeup from idle path that the tick
* broadcast device expired for us, we don't want to go deep
* idle as we know that the IPI is going to arrive right away.
*/
if (cpu_idle_force_poll || tick_check_broadcast_expired()) {
tick_nohz_idle_restart_tick();
cpu_idle_poll();
} else {
cpuidle_idle_call();
}
arch_cpu_idle_exit();
}
/*
* Since we fell out of the loop above, we know TIF_NEED_RESCHED must
* be set, propagate it into PREEMPT_NEED_RESCHED.
*
* This is required because for polling idle loops we will not have had
* an IPI to fold the state for us.
*/
preempt_set_need_resched();
tick_nohz_idle_exit();
__current_clr_polling();
/*
* We promise to call sched_ttwu_pending() and reschedule if
* need_resched() is set while polling is set. That means that clearing
* polling needs to be visible before doing these things.
*/
smp_mb__after_atomic();
/*
* RCU relies on this call to be done outside of an RCU read-side
* critical section.
*/
flush_smp_call_function_queue();
schedule_idle();
if (unlikely(klp_patch_pending(current)))
klp_update_patch_state(current);
}
bool cpu_in_idle(unsigned long pc)
{
return pc >= (unsigned long)__cpuidle_text_start &&
pc < (unsigned long)__cpuidle_text_end;
}
struct idle_timer {
struct hrtimer timer;
int done;
};
static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer)
{
struct idle_timer *it = container_of(timer, struct idle_timer, timer);
WRITE_ONCE(it->done, 1);
set_tsk_need_resched(current);
return HRTIMER_NORESTART;
}
void play_idle_precise(u64 duration_ns, u64 latency_ns)
{
struct idle_timer it;
/*
* Only FIFO tasks can disable the tick since they don't need the forced
* preemption.
*/
WARN_ON_ONCE(current->policy != SCHED_FIFO);
WARN_ON_ONCE(current->nr_cpus_allowed != 1);
WARN_ON_ONCE(!(current->flags & PF_KTHREAD));
WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY));
WARN_ON_ONCE(!duration_ns);
WARN_ON_ONCE(current->mm);
rcu_sleep_check();
preempt_disable();
current->flags |= PF_IDLE;
cpuidle_use_deepest_state(latency_ns);
it.done = 0;
hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
it.timer.function = idle_inject_timer_fn;
hrtimer_start(&it.timer, ns_to_ktime(duration_ns),
HRTIMER_MODE_REL_PINNED_HARD);
while (!READ_ONCE(it.done))
do_idle();
cpuidle_use_deepest_state(0);
current->flags &= ~PF_IDLE;
preempt_fold_need_resched();
preempt_enable();
}
EXPORT_SYMBOL_GPL(play_idle_precise);
void cpu_startup_entry(enum cpuhp_state state)
{
arch_cpu_idle_prepare();
cpuhp_online_idle(state);
while (1)
do_idle();
}
/*
* idle-task scheduling class.
*/
#ifdef CONFIG_SMP
static int
select_task_rq_idle(struct task_struct *p, int cpu, int flags)
{
return task_cpu(p); /* IDLE tasks as never migrated */
}
static int
balance_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
return WARN_ON_ONCE(1);
}
#endif
/*
* Idle tasks are unconditionally rescheduled:
*/
static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
{
resched_curr(rq);
}
static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
{
}
static void set_next_task_idle(struct rq *rq, struct task_struct *next, bool first)
{
update_idle_core(rq);
schedstat_inc(rq->sched_goidle);
}
#ifdef CONFIG_SMP
static struct task_struct *pick_task_idle(struct rq *rq)
{
return rq->idle;
}
#endif
struct task_struct *pick_next_task_idle(struct rq *rq)
{
struct task_struct *next = rq->idle;
set_next_task_idle(rq, next, true);
return next;
}
/*
* It is not legal to sleep in the idle task - print a warning
* message if some code attempts to do it:
*/
static void
dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
{
raw_spin_rq_unlock_irq(rq);
printk(KERN_ERR "bad: scheduling from the idle thread!\n");
dump_stack();
raw_spin_rq_lock_irq(rq);
}
/*
* scheduler tick hitting a task of our scheduling class.
*
* NOTE: This function can be called remotely by the tick offload that
* goes along full dynticks. Therefore no local assumption can be made
* and everything must be accessed through the @rq and @curr passed in
* parameters.
*/
static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
{
}
static void switched_to_idle(struct rq *rq, struct task_struct *p)
{
BUG();
}
static void
prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
{
BUG();
}
static void update_curr_idle(struct rq *rq)
{
}
/*
* Simple, special scheduling class for the per-CPU idle tasks:
*/
DEFINE_SCHED_CLASS(idle) = {
/* no enqueue/yield_task for idle tasks */
/* dequeue is not valid, we print a debug message there: */
.dequeue_task = dequeue_task_idle,
.check_preempt_curr = check_preempt_curr_idle,
.pick_next_task = pick_next_task_idle,
.put_prev_task = put_prev_task_idle,
.set_next_task = set_next_task_idle,
#ifdef CONFIG_SMP
.balance = balance_idle,
.pick_task = pick_task_idle,
.select_task_rq = select_task_rq_idle,
.set_cpus_allowed = set_cpus_allowed_common,
#endif
.task_tick = task_tick_idle,
.prio_changed = prio_changed_idle,
.switched_to = switched_to_idle,
.update_curr = update_curr_idle,
};