Re: S3 resume regression [1cf4f629d9d2 ("cpu/hotplug: Move online calls to hotplugged cpu")]

[Thomas Gleixner]

On Fri, 28 Oct 2016, Ville Syrjälä wrote:
> On Thu, Oct 27, 2016 at 10:41:18PM +0200, Thomas Gleixner wrote:
> > On Thu, 27 Oct 2016, Ville Syrjälä wrote:
> > > On Thu, Oct 27, 2016 at 09:25:05PM +0200, Thomas Gleixner wrote:
> > > > So it would be interesting whether that hunk in resume_broadcast() is
> > > > sufficient.
> > > 
> > > So far it looks like the answer is yes.
> > > 
> > > Looks to be about 5 seconds slower than acpi-idle in resuming, but
> > > I suppose that's not all that surprising ;)
> > 
> > Well, set it to 1msec then. If that works reliably then we really can do
> > that unconditionally. There is no harm in firing a useless timer during
> > resume once.
> 
> I narrowed down the required timeout, and looks like 25ms is the
> minimum that works. With 24ms I already started to have failures. So
> maybe just bump it up by an order of magnitude to 250ms for some
> safety margin?

Sure, but what puzzles me is that we need a timeout that big. What happens
between broadcast_resume() and broadcast_resume() + 25ms?

IOW, what is the event/resume function which we need to bridge. We should
really try to track than down.

You might try to enable function tracing and do a tracing_off() when that
25ms timeout fires.

Something like 

	stop_trace = true;

in broadcast_resume() and then in the broadcast timer function:

	if (stop_trace) {
		stop_trace = false;
		tracing_off();
	}

Then when the machine is up read the trace, compress and upload it
somewhere or send it in private mail if it's not that big.

Thanks,

	tglx