On 07/07/2014 03:40 PM, Todd Poynor wrote:
On Mon, Jul 7, 2014 at 12:30 PM, Saravana Kannan <skannan@xxxxxxxxxxxxxx> wrote:
...
Though these are the requirements I have from them:
- On hotplug files values should get reset ..
- On suspend/resume values must be retained.
Hmm... There's actually enough interest in NOT reseting across hotplug
because it's also used by thermal when a CPU gets too hot and then it's
plugged in later. So, userspace has no way to cleanly restore the values.
But that's a separate topic.
For Android's usage we're also interested in both:
1. not removing and recreating the cpufreq sysfs files for a CPU on
hotplug events (we currently use hotplug uevents to reset file
ownership such that power policy can be controlled by non-root).
Ah thanks! This is another good point towards leaving the sysfs nodes
alone that I forgot about.
2. not resetting the contents of policy files such as scaling_max_freq
(also fixed up from uevents) or stats files (we currently keep a
separate persistent time_in_state for battery accounting purposes).
Any objections to leaving them alone during hotplug? If those files are
read/written to when the entire cluster is hotplugged off, we could just
return an error. I'm not saying it would be impossible to fix all these
deadlock and race issues in the current code -- but it seems like a lot
of
pointless effort to remove/add sysfs nodes.
No objections from our standpoint.
Thanks,
-Saravana
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