Messages in this thread | | | Date | Wed, 26 Feb 2014 11:32:19 +0530 | Subject | Re: [PATCH] cpufreq: Set policy to non-NULL only after all hotplug online work is done | From | Viresh Kumar <> |
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On 26 February 2014 07:18, Saravana Kannan <skannan@codeaurora.org> wrote: > On 02/25/2014 02:41 PM, Rafael J. Wysocki wrote:
>> And is "fully initialized" actually well defined? > > The point in add dev/hot plug path after which we will no longer change > policy fields without sending further CPUFREQ_UPDATE_POLICY_CPU / > CPUFRE_NOTIFY notifiers.
Okay..
> Pretty much the end of __cpufreq_add_dev() so that it's after: > - cpufreq_init_policy() > - And the update of userpolicy fields that after thie init call
No. In that case it can be considered initialized before cpufreq_init_policy(). As we do send CPUFREQ_NOTIFY after that from cpufreq_init_policy()-> cpufreq_set_policy().
There are two types of fields within policy, some are very basic: cpu/min/max/ affected_cpus/related_cpus
some are advanced: sysfs/governors/..
And as a rule you have to get policy->rwsem lock before accessing policy members. We might not have followed it very well for small things like cpu.
And so if you are doing anything over that, please use a lock and that is already present in cpufreq_update_policy().
With my latest patchset that I sent yesterday, locking is improved and now a policy will be usable only after the rwsem is released. And that should be fine. And so making it available in the per-cpu variable after all the necessary fields are filled looks fine to me. And so I don't think we need to move it after call to cpufreq_init_policy(maybe a better name to this function is required)..
> Ok, here's some pseudo code to explain it better: > > Something like, replace all calls to cpufreq_driver->get with > __cpufreq_driver_get() with the fn being something like: > > unsigned int __cpufreq_driver_get(cpufreq_policy *policy) > { > if (policy->clk) > return clk_get_rate(policy->clk) / 1000; > else > return cpufreq_driver->get(policy->cpu);
This part may still use cpufreq_cpu_get().
> }
Drivers are free to have their implementation of ->get() even if they have a valid policy->clk field..
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