Re: [PATCH v3]PM/Sleep: Timer quiesce in freeze state

[Thomas Gleixner <tglx@linutronix.de>]

On Mon, 26 Jan 2015, Rafael J. Wysocki wrote:
> On Monday, January 26, 2015 03:24:27 PM Thomas Gleixner wrote:
> > On Mon, 26 Jan 2015, Rafael J. Wysocki wrote:
> > > On Monday, January 26, 2015 10:40:24 AM Thomas Gleixner wrote:
> > > > The only remaining issue might be a NMI calling into
> > > > ktime_get_mono_fast_ns() before timekeeping is resumed. Its probably a
> > > > non issue on x86/tsc, but it might be a problem on other platforms
> > > > which turn off devices, clocks, It's not rocket science to prevent
> > > > that.
> > > 
> > > I don't see any users of ktime_get_mono_fast_ns() at all, unless some non-trivial
> > > macros are involved.  At least grepping for it only returns the definition,
> > > declarations and the line in trace.c.
> > 
> > You can trace in NMI and perf is going to use ktime_get_mono_fast_ns()
> > eventually as well.
> 
> So I'm not sure how to intercept that to be honest.  Any hints?

If we suspend timekeeping we can make the fast timekeeper point at a
dummy readout function which returns the time at suspend, if the clock
source does not resume automagically.

As I said TSC should be a non issue, but other stuff might be. We
could make it conditional on CLOCK_SOURCE_SUSPEND_NONSTOP perhaps.

Thanks,

	tglx