From: Sudeep Holla <sudeep.holla@arm.com>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: "Rafael J . Wysocki" <rjw@rjwysocki.net>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
linux-pm@vger.kernel.org, Viresh Kumar <viresh.kumar@linaro.org>,
Liviu Dudau <liviu.dudau@arm.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Sudeep Holla <sudeep.holla@arm.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Lukasz Luba <lukasz.luba@arm.com>
Subject: Re: [PATCH] cpufreq: vexpress-spc: Fix wrong alternation of policy->related_cpus during CPU hp
Date: Wed, 27 Nov 2019 12:08:16 +0000 [thread overview]
Message-ID: <20191127120816.GC29301@bogus> (raw)
In-Reply-To: <20191127114801.23837-1-dietmar.eggemann@arm.com>
On Wed, Nov 27, 2019 at 12:48:01PM +0100, Dietmar Eggemann wrote:
> Since commit ca74b316df96 ("arm: Use common cpu_topology structure and
> functions.") the core cpumask has to be modified during cpu hotplug
> operations.
>
> ("arm: Fix topology setup in case of CPU hotplug for CONFIG_SCHED_MC")
> [1] fixed that but revealed another issue on TC2, i.e in its cpufreq
> driver.
>
> During CPU hp stress operations on multiple CPUs, policy->related_cpus
> can be altered. This is wrong since this cpumask should contain the
> online and offline CPUs.
>
> The WARN_ON(!cpumask_test_cpu(cpu, policy->related_cpus)) in
> cpufreq_online() triggers in this case.
>
> The core cpumask can't be used to set the policy->cpus in
> ve_spc_cpufreq_init() anymore in case it is called via
> cpuhp_cpufreq_online()->cpufreq_online()->cpufreq_driver->init().
>
> An empty online() callback can be used to avoid that the init()
> driver function is called during CPU hotplug in so that
> policy->related_cpus will not be changed.
>
Unlike DT based drivers, it not easy to get the fixed cpumask unless we
add some mechanism to extract it based on clks/OPP added. I prefer
this simple solution instead.
> Implementing an online() also requires an offline() callback.
>
> Tested on TC2 with CPU hp stress test (CPU hp from multiple CPUs at
> the same time).
>
> [1]
> https://lore.kernel.org/r/20191127103353.12417-1-dietmar.eggemann@arm.com
>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
--
Regards,
Sudeep
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next prev parent reply other threads:[~2019-11-27 12:08 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 11:48 [PATCH] cpufreq: vexpress-spc: Fix wrong alternation of policy->related_cpus during CPU hp Dietmar Eggemann
2019-11-27 12:07 ` Viresh Kumar
2019-11-27 12:10 ` Sudeep Holla
2019-11-27 12:08 ` Sudeep Holla [this message]
2019-11-27 12:14 ` Viresh Kumar
2019-11-27 13:32 ` Sudeep Holla
2019-11-27 14:58 ` Dietmar Eggemann
2019-11-27 15:40 ` Sudeep Holla
2019-11-27 18:45 ` Sudeep Holla
2019-11-28 2:31 ` Viresh Kumar
2019-11-28 10:01 ` Dietmar Eggemann
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