Re: [RFC PATCH 11/19] cpufreq: assert policy->rwsem is held in __cpufreq_governor

[Viresh Kumar]

On 01-02-16, 12:24, Saravana Kannan wrote:
> On 02/01/2016 02:22 AM, Rafael J. Wysocki wrote:
> I'm not sure whose idea you are referring to. Viresh's (I don't think I saw
> his proposal) or mine.

http://git.linaro.org/people/viresh.kumar/linux.git/commit/57714d5b1778f2f610bcc5c74d85b29ba1cc1995

> Anyway, to explain my suggestion better, I'm proposing to make it so that we
> don't have a need for the AB BA locking. The only reason the governor needs
> to even grab the sysfs lock is to add/remove the sysfs attribute files.
> 
> That can be easily achieved if the policy struct has some "gov_attrs"
> field(s) that each governor populates. Then the framework just has to create
> them after POLICY_INIT is processed by the governor and remove them before
> POILICY_EXIT is sent to the governor.

What will that solve? It will stay exactly same then as well, as we
would be adding/removing these attributes from within the same
policy->rwsem ..

> That way, we also avoid having to worry about the gov attributes accessed by
> the show/store disappearing while the files are being accessed.

It can't happen. S_active lock should be taking care of that, isn't
it?

-- 
viresh