Messages in this thread | | | Date | Wed, 27 Nov 2019 12:08:16 +0000 | From | Sudeep Holla <> | Subject | Re: [PATCH] cpufreq: vexpress-spc: Fix wrong alternation of policy->related_cpus during CPU hp |
| |
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
| |