On Thu, Aug 20, 2020 at 10:36:43AM -0400, Steven Rostedt wrote:
>
> I tested this series on top of tip/master and triggered the below
> warning when running the irqsoff tracer boot up test (config attached).
>
> -- Steve
>
> Testing tracer irqsoff:
>
> =============================
> WARNING: suspicious RCU usage
> 5.9.0-rc1-test+ #92 Not tainted
> -----------------------------
> include/trace/events/lock.h:13 suspicious rcu_dereference_check() usage!
>
> other info that might help us debug this:
>
>
> rcu_scheduler_active = 2, debug_locks = 1
> RCU used illegally from extended quiescent state!
> no locks held by swapper/2/0.
>
> stack backtrace:
> CPU: 2 PID: 0 Comm: swapper/2 Not tainted 5.9.0-rc1-test+ #92
> Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03
> 07/14/2016
> Call Trace:
> dump_stack+0x8d/0xc0
> lock_acquire.cold+0x23/0x2c
> ? default_idle_call+0x4d/0x210
> _raw_spin_lock_irqsave+0x50/0xa0
> ? check_critical_timing+0x69/0x160
> check_critical_timing+0x69/0x160
> ? default_idle_call+0x4d/0x210
> stop_critical_timings+0xdd/0xf0
> default_idle_call+0x4d/0x210
> do_idle+0x1f6/0x260
> cpu_startup_entry+0x19/0x20
> start_secondary+0x110/0x140
> secondary_startup_64+0xb6/0xc0
Shiny, I think that wants something like the below, but let me go frob
my config and test it.
---
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -151,8 +151,8 @@ static void enter_s2idle_proper(struct c
* cpuidle mechanism enables interrupts and doing that with timekeeping
* suspended is generally unsafe.
*/
- rcu_idle_enter();
stop_critical_timings();
+ rcu_idle_enter();
drv->states[index].enter_s2idle(dev, drv, index);
if (WARN_ON_ONCE(!irqs_disabled()))
local_irq_disable();
@@ -164,8 +164,8 @@ static void enter_s2idle_proper(struct c
* FIXME, order against rcu_idle_exit ?
*/
RCU_NONIDLE(tick_unfreeze());
- start_critical_timings();
rcu_idle_exit();
+ start_critical_timings();
time_end = ns_to_ktime(local_clock());
@@ -236,11 +236,11 @@ int cpuidle_enter_state(struct cpuidle_d
trace_cpu_idle(index, dev->cpu);
time_start = ns_to_ktime(local_clock());
- rcu_idle_enter();
stop_critical_timings();
+ rcu_idle_enter();
entered_state = target_state->enter(dev, drv, index);
- start_critical_timings();
rcu_idle_exit();
+ start_critical_timings();
sched_clock_idle_wakeup_event();
time_end = ns_to_ktime(local_clock());
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -55,16 +55,16 @@ __setup("hlt", cpu_idle_nopoll_setup);
static noinline int __cpuidle cpu_idle_poll(void)
{
trace_cpu_idle(0, smp_processor_id());
+ stop_critical_timings();
rcu_idle_enter();
local_irq_enable();
- stop_critical_timings();
while (!tif_need_resched() &&
(cpu_idle_force_poll || tick_check_broadcast_expired()))
cpu_relax();
- start_critical_timings();
rcu_idle_exit();
+ start_critical_timings();
trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
return 1;
@@ -91,11 +91,11 @@ void __cpuidle default_idle_call(void)
if (current_clr_polling_and_test()) {
local_irq_enable();
} else {
- rcu_idle_enter();
stop_critical_timings();
+ rcu_idle_enter();
arch_cpu_idle();
- start_critical_timings();
rcu_idle_exit();
+ start_critical_timings();
}
}
