Re: WARNING: suspicious RCU usage - sdhci-pltfm: SDHCI platform and OF driver helper

[peterz]

On Wed, Sep 02, 2020 at 09:03:37AM +0200, Ulf Hansson wrote:
> Lots of cpuidle drivers are using CPU_PM notifiers (grep for
> cpu_pm_enter and you will see) from their idlestates ->enter()
> callbacks. And for those we are already calling
> rcu_irq_enter_irqson|off() in cpu_pm_notify() when firing them.

Yeah, that particular trainwreck is on my todo list already ... then
again, that list is forever overflowing.

I'm thinking cpu_pm_unregister_notifier() is not a common thing? The few
I looked at seem to suggest 'never' is a good approximation.

It would be fairly trivial to replace the atomic_notifier usage with a
raw_notifier a lock and either stop-machine or IPIs. Better still would
be if we can get rid of it entirely, but I can't tell in a hurry if that
is possible.