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Date:   Wed, 2 Sep 2020 14:13:55 +0200
From:   peterz@infradead.org
To:     Ulf Hansson <ulf.hansson@linaro.org>
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        Lina Iyer <ilina@codeaurora.org>,
        Naresh Kamboju <naresh.kamboju@linaro.org>,
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        Linux PM <linux-pm@vger.kernel.org>,
        Anders Roxell <anders.roxell@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Rajendra Nayak <rnayak@codeaurora.org>,
        John Stultz <john.stultz@linaro.org>,
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        Viresh Kumar <viresh.kumar@linaro.org>,
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Subject: Re: WARNING: suspicious RCU usage - sdhci-pltfm: SDHCI platform and
 OF driver helper
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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.