Peter Zijlstra
2022-Jun-08 14:27 UTC
[PATCH 15/36] cpuidle, cpu_pm: Remove RCU fiddling from cpu_pm_{enter, exit}()
All callers should still have RCU enabled.
Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
---
kernel/cpu_pm.c | 9 ---------
1 file changed, 9 deletions(-)
--- a/kernel/cpu_pm.c
+++ b/kernel/cpu_pm.c
@@ -30,16 +30,9 @@ static int cpu_pm_notify(enum cpu_pm_eve
{
int ret;
- /*
- * This introduces a RCU read critical section, which could be
- * disfunctional in cpu idle. Copy RCU_NONIDLE code to let RCU know
- * this.
- */
- rcu_irq_enter_irqson();
rcu_read_lock();
ret = raw_notifier_call_chain(&cpu_pm_notifier.chain, event, NULL);
rcu_read_unlock();
- rcu_irq_exit_irqson();
return notifier_to_errno(ret);
}
@@ -49,11 +42,9 @@ static int cpu_pm_notify_robust(enum cpu
unsigned long flags;
int ret;
- rcu_irq_enter_irqson();
raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags);
ret = raw_notifier_call_chain_robust(&cpu_pm_notifier.chain, event_up,
event_down, NULL);
raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags);
- rcu_irq_exit_irqson();
return notifier_to_errno(ret);
}
Mark Rutland
2022-Jun-14 16:13 UTC
[PATCH 15/36] cpuidle,cpu_pm: Remove RCU fiddling from cpu_pm_{enter,exit}()
On Wed, Jun 08, 2022 at 04:27:38PM +0200, Peter Zijlstra wrote:> All callers should still have RCU enabled.IIUC with that true we should be able to drop the RCU_NONIDLE() from drivers/perf/arm_pmu.c, as we only needed that for an invocation via a pm notifier. I should be able to give that a spin on some hardware.> > Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org> > --- > kernel/cpu_pm.c | 9 --------- > 1 file changed, 9 deletions(-) > > --- a/kernel/cpu_pm.c > +++ b/kernel/cpu_pm.c > @@ -30,16 +30,9 @@ static int cpu_pm_notify(enum cpu_pm_eve > { > int ret; > > - /* > - * This introduces a RCU read critical section, which could be > - * disfunctional in cpu idle. Copy RCU_NONIDLE code to let RCU know > - * this. > - */ > - rcu_irq_enter_irqson(); > rcu_read_lock(); > ret = raw_notifier_call_chain(&cpu_pm_notifier.chain, event, NULL); > rcu_read_unlock(); > - rcu_irq_exit_irqson();To make this easier to debug, is it worth adding an assertion that RCU is watching here? e.g. RCU_LOCKDEP_WARN(!rcu_is_watching(), "cpu_pm_notify() used illegally from EQS");> > return notifier_to_errno(ret); > } > @@ -49,11 +42,9 @@ static int cpu_pm_notify_robust(enum cpu > unsigned long flags; > int ret; > > - rcu_irq_enter_irqson(); > raw_spin_lock_irqsave(&cpu_pm_notifier.lock, flags); > ret = raw_notifier_call_chain_robust(&cpu_pm_notifier.chain, event_up, event_down, NULL); > raw_spin_unlock_irqrestore(&cpu_pm_notifier.lock, flags); > - rcu_irq_exit_irqson();... and likewise here? Thanks, Mark.> > return notifier_to_errno(ret); > } > >