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Message-ID: <8f37d1cc-41d9-ad4b-ec84-708f1db03e89@linaro.org>
Date:   Thu, 12 Jan 2023 12:27:40 +0100
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Subject: Re: [PATCH v2 1/5] PM: domains: Add GENPD_FLAG_RT_SAFE for PREEMPT_RT
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To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     Ulf Hansson <ulf.hansson@linaro.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Kevin Hilman <khilman@kernel.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Lorenzo Pieralisi <lpieralisi@kernel.org>,
        Sudeep Holla <sudeep.holla@arm.com>, linux-pm@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Adrien Thierry <athierry@redhat.com>,
        Brian Masney <bmasney@redhat.com>,
        linux-rt-users@vger.kernel.org
References: <20221219151503.385816-1-krzysztof.kozlowski@linaro.org>
 <20221219151503.385816-2-krzysztof.kozlowski@linaro.org>
 <CAPDyKFrVjenwv0Fe36LBqML-R_w2TjoCwmbnqqOohV_1zH8vJQ@mail.gmail.com>
 <9771639f-5172-8f3b-3ce6-8fd195aa95b3@linaro.org>
 <Y7/inz5ZoQiR3bP3@linutronix.de>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <Y7/inz5ZoQiR3bP3@linutronix.de>
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On 12/01/2023 11:36, Sebastian Andrzej Siewior wrote:
> On 2023-01-06 15:52:57 [+0100], Krzysztof Kozlowski wrote:
>>> Just so I don't get this wrong, since the cpuidle-psci also calls
>>> pm_runtime_* functions so it isn't PREEMPT_RT safe, at least not yet?
>>
>> You are correct. Patch 3 here addresses it by... just not doing runtime
>> PM. This is a hacky workaround but:
>> 1. I don't have any other idea,
>> 2. It's not a big problem because RT systems are not supposed to have
>> any CPU idle (one of first things during RT system tuning is to disable
>> cpuidle).
> 
> so you say you use idle=poll instead? 

This was generic comment that system is not supposed to go into deeper
idle states.

Best regards,
Krzysztof