On Tue, Jun 14, 2022 at 05:13:16PM +0100, Mark Rutland wrote:
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@xxxxxxxxxxxxx>
---
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");
My understanding is that rcu_read_lock() implies something along those
lines when PROVE_RCU.
