Re: [RFC v0 2/9] suspend: Add getter function to report if freezing is active

From: Rafael J. Wysocki
Date: Mon Sep 07 2015 - 09:14:43 EST

On Monday, September 07, 2015 10:55:43 AM Daniel Wagner wrote:
> On 09/05/2015 04:11 AM, Rafael J. Wysocki wrote:
> > On Friday, September 04, 2015 03:34:55 PM Daniel Wagner wrote:
> >> Instead encode the FREEZE state via the CPU state we allow the
> >> interesting subsystems (MCE, microcode) to query the power
> >> subsystem directly.
> >
> > A use case, please.
> The motivation for this change is to reduce the complexity in the
> hotplug code. As tried to point out in the cover letter, the FROZEN
> bits have only a bunch of users after all those years (2007). So it is
> worth to have all the notifier users to handle the FROZEN state?
> Don't know if that counts as use case.
> >> Most notifiers are not interested at all
> >> in this information so rather have explicit calls to freeze_active()
> >> instead adding complexity to the rest of the users of the CPU
> >> notifiers.
> >
> > Why does it has anything to do with CPU notifiers?
> cpu_{down|up} will call the notifiers with the CPU_TASK_FROZEN bit set
> and so most notifiers are doing
> switch (actcion ~CPU_TASK_FROZEN)
> to filter it out because they don't need to handle the system wide
> ongoing freeze operations.
> > We don't offline CPUs for suspend-to-idle.
> Sure. As I said the motivation is to reduce the complexity in the
> hotplug code.

Well, it looks like I confused two things.

Let me look at this again.


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