Re: [PATCH 2/5] cpufreq: governor: Create separate sysfs-ops

Viresh Kumar
2016-02-03T06:57:50Z

On 02-02-16, 20:03, Saravana Kannan wrote:
> This is the hotplug case I mentioned. The sysfs file removals will happen
> only for the last CPU in that policy (we thankfully optimized that part last
> year). We also know that multiple CPUs can't be hotplugged at the same time.
> So, in the start of cpufreq_offline_prepare, we just need to check if this
> is the last CPU in the policy and if that's the case, do the gov sysfs
> remove and then grab the policy lock and do all our crap. If a read is going
> on, that's going to finish before the sysfs attr remove can go ahead and it
> can grab the policy lock if it needs to and that still won't cause a
> deadlock because we haven't yet grabbed the policy lock in
> cpufreq_offline_prepare(). If the read comes after the sysfs remove, then
> the read is obviously going to fail (we can depend on the sysfs framework on
> doing its job there).

IMHO, these are all dirty hacks we should stay away from. Adding such
hunks in code is considered a band-aid kind of solution and hurts
readability badly. The new solution (new governor show/store)
implement this in a very clean and proper way I feel..

Others are free to disagree though :)

--
viresh