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sched,idle,rcu: Push rcu_idle deeper into the idle path 

Lots of things take locks, due to a wee bug, rcu_lockdep didn't notice
that the locking tracepoints were using RCU.

Push rcu_idle_{enter,exit}() as deep as possible into the idle paths,
this also resolves a lot of _rcuidle()/RCU_NONIDLE() usage.

Specifically, sched_clock_idle_wakeup_event() will use ktime which
will use seqlocks which will tickle lockdep, and
stop_critical_timings() uses lock.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Marco Elver <elver@google.com>
Link: https://lkml.kernel.org/r/20200821085348.310943801@infradead.org
This commit is contained in:
Peter Zijlstra 2020-08-07 20:50:19 +02:00
parent 49d9c59363
commit 1098582a0f
2 changed files with 17 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/cpuidle/cpuidle.c
View File

@ -145,13 +145,14 @@ static void enter_s2idle_proper(struct cpuidle_driver *drv,
* executing it contains RCU usage regarded as invalid in the idle
* context, so tell RCU about that.
*/
RCU_NONIDLE(tick_freeze());
tick_freeze();
/*
* The state used here cannot be a "coupled" one, because the "coupled"
* cpuidle mechanism enables interrupts and doing that with timekeeping
* suspended is generally unsafe.
*/
stop_critical_timings();
rcu_idle_enter();
drv->states[index].enter_s2idle(dev, drv, index);
if (WARN_ON_ONCE(!irqs_disabled()))
local_irq_disable();
@ -160,7 +161,8 @@ static void enter_s2idle_proper(struct cpuidle_driver *drv,
* first CPU executing it calls functions containing RCU read-side
* critical sections, so tell RCU about that.
*/
RCU_NONIDLE(tick_unfreeze());
rcu_idle_exit();
tick_unfreeze();
start_critical_timings();
time_end = ns_to_ktime(local_clock());
@ -229,16 +231,18 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
/* Take note of the planned idle state. */
sched_idle_set_state(target_state);
trace_cpu_idle_rcuidle(index, dev->cpu);
trace_cpu_idle(index, dev->cpu);
time_start = ns_to_ktime(local_clock());
stop_critical_timings();
rcu_idle_enter();
entered_state = target_state->enter(dev, drv, index);
rcu_idle_exit();
start_critical_timings();
sched_clock_idle_wakeup_event();
time_end = ns_to_ktime(local_clock());
trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu);
/* The cpu is no longer idle or about to enter idle. */
sched_idle_set_state(NULL);

24
kernel/sched/idle.c
View File

@ -54,17 +54,18 @@ __setup("hlt", cpu_idle_nopoll_setup);
static noinline int __cpuidle cpu_idle_poll(void)
{
rcu_idle_enter();
trace_cpu_idle_rcuidle(0, smp_processor_id());
local_irq_enable();
trace_cpu_idle(0, smp_processor_id());
stop_critical_timings();
rcu_idle_enter();
local_irq_enable();
while (!tif_need_resched() &&
(cpu_idle_force_poll || tick_check_broadcast_expired()))
(cpu_idle_force_poll || tick_check_broadcast_expired()))
cpu_relax();
start_critical_timings();
trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
rcu_idle_exit();
start_critical_timings();
trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
return 1;
}
@ -91,7 +92,9 @@ void __cpuidle default_idle_call(void)
local_irq_enable();
} else {
stop_critical_timings();
rcu_idle_enter();
arch_cpu_idle();
rcu_idle_exit();
start_critical_timings();
}
}
@ -158,7 +161,6 @@ static void cpuidle_idle_call(void)
if (cpuidle_not_available(drv, dev)) {
tick_nohz_idle_stop_tick();
rcu_idle_enter();
default_idle_call();
goto exit_idle;
@ -178,21 +180,17 @@ static void cpuidle_idle_call(void)
u64 max_latency_ns;
if (idle_should_enter_s2idle()) {
rcu_idle_enter();
entered_state = call_cpuidle_s2idle(drv, dev);
if (entered_state > 0)
goto exit_idle;
rcu_idle_exit();
max_latency_ns = U64_MAX;
} else {
max_latency_ns = dev->forced_idle_latency_limit_ns;
}
tick_nohz_idle_stop_tick();
rcu_idle_enter();
next_state = cpuidle_find_deepest_state(drv, dev, max_latency_ns);
call_cpuidle(drv, dev, next_state);
@ -209,8 +207,6 @@ static void cpuidle_idle_call(void)
else
tick_nohz_idle_retain_tick();
rcu_idle_enter();
entered_state = call_cpuidle(drv, dev, next_state);
/*
* Give the governor an opportunity to reflect on the outcome
@ -226,8 +222,6 @@ exit_idle:
*/
if (WARN_ON_ONCE(irqs_disabled()))
local_irq_enable();
rcu_idle_exit();
}
/*