linux-kernel - Re: [PATCH v3] cpuidle: psci: Do not suspend topology CPUs on PREEMPT

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Message-ID: <Y9eWF1wZe0p6Gzmq@linutronix.de>
Date:   Mon, 30 Jan 2023 11:04:07 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Adrien Thierry <athierry@...hat.com>,
        Brian Masney <bmasney@...hat.com>,
        linux-rt-users@...r.kernel.org
Subject: Re: [PATCH v3] cpuidle: psci: Do not suspend topology CPUs on
 PREEMPT_RT

On 2023-01-25 11:08:04 [+0100], Ulf Hansson wrote:
> > It's the power domain sued for other devices, so we need it. Otherwise
> > other devices will keep waiting for this missing power domain provider.
> 
Ach this explains my other question I had.
> 
> And we are still able to use those idle states that are solely per
> CPU, which is probably nice to have. No?

If the entry/ exit latency is not known, it can be dangerous.

> Kind regards
> Uffe

Sebastian