Messages in this thread | | | Date | Wed, 27 Nov 2019 12:10:25 +0000 | From | Sudeep Holla <> | Subject | Re: [PATCH] cpufreq: vexpress-spc: Fix wrong alternation of policy->related_cpus during CPU hp |
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On Wed, Nov 27, 2019 at 05:37:44PM +0530, Viresh Kumar wrote: > On 27-11-19, 12:48, 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. > > > > 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 > > > > Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> > > Wanna provide any fixes tag ? > > > --- > > drivers/cpufreq/vexpress-spc-cpufreq.c | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > This is 5.5 material or 5.6 ? >
v5.5 for sure, broken even on v5.4 but unless someone really cares for stable on TC2, I am happy to skip it.
-- Regards, Sudeep
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