linux-kernel - Re: [PATCH v2 2/7] cpufreq/sched: Move cpufreq-specific EAS checks to cpufreq

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Message-ID: <CAJZ5v0jVy1DeiRgDdUG0q--7NTi26yYjuezL3it641pQcjyN9g@mail.gmail.com>
Date: Mon, 12 May 2025 19:47:32 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Marek Szyprowski <m.szyprowski@...sung.com>, 
	"Rafael J. Wysocki" <rjw@...ysocki.net>, Linux PM <linux-pm@...r.kernel.org>, 
	LKML <linux-kernel@...r.kernel.org>, Lukasz Luba <lukasz.luba@....com>, 
	Peter Zijlstra <peterz@...radead.org>, 
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>, 
	Morten Rasmussen <morten.rasmussen@....com>, Vincent Guittot <vincent.guittot@...aro.org>, 
	Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>, 
	Pierre Gondois <pierre.gondois@....com>, Christian Loehle <christian.loehle@....com>
Subject: Re: [PATCH v2 2/7] cpufreq/sched: Move cpufreq-specific EAS checks to cpufreq

On Mon, May 12, 2025 at 7:24 PM Dietmar Eggemann
<dietmar.eggemann@....com> wrote:
>
> On 12/05/2025 14:53, Rafael J. Wysocki wrote:
> > On Mon, May 12, 2025 at 8:48 AM Marek Szyprowski
> > <m.szyprowski@...sung.com> wrote:
> >>
> >> On 10.05.2025 13:31, Rafael J. Wysocki wrote:
> >>> On Sat, May 10, 2025 at 1:49 AM Marek Szyprowski
> >>> <m.szyprowski@...sung.com> wrote:
> >>>> On 06.05.2025 22:37, Rafael J. Wysocki wrote:
> >>>>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> [...]
>
> >>>>    *** DEADLOCK ***
> >>> Well, it turns out that trying to acquire policy->rwsem under
> >>> sched_domains_mutex is a bad idea.  It was added to
> >>> cpufreq_policy_is_good_for_eas() to address a theoretical race, so it
> >>> can be dropped safely.  A theoretical race is better than a real
> >>> deadlock.
> >>>
> >>> Please test the attached patch.
> >>
> >> This fixed the observed issue. Thanks!
> >>
> >> Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
> >> Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
> >
> > Thanks for the confirmation!
>
> See this on my Hikey 960 as well. I was wondering why Christian L. and I
> didn't catch this with RFT v1.0 (*) on i7-13700K.
>
> But it looks like that
>
> https://web.git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git/log/?h=experimental/intel_pstate/eas-take2-extended
>
> mentioned in the patch-header of (*) didn't have this line in its
>
> commit 9ad047cade6b ("cpufreq/sched: Move cpufreq-specific EAS checks to
> cpufreq")

Yeah, I made this change later.  My bad.