On Wed, 6 Jan 2016, John Stultz wrote:
> On Wed, Jan 6, 2016 at 5:00 AM, Prarit Bhargava <[email protected]> wrote:
> > -ktime_t ktime_get_with_offset(enum tk_offsets offs)
> > +ktime_t ktime_get_with_offset(enum tk_offsets offs, int trylock)
> > {
> > struct timekeeper *tk = &tk_core.timekeeper;
> > unsigned int seq;
> > ktime_t base, *offset = offsets[offs];
> > s64 nsecs;
> > + unsigned long flags = 0;
> > +
> > + if (unlikely(!timekeeping_initialized))
> > + return ktime_set(0, 0);
> >
> > WARN_ON(timekeeping_suspended);
> >
> > + if (trylock && !raw_spin_trylock_irqsave(&timekeeper_lock, flags))
> > + return ktime_set(KTIME_MAX, 0);
>
> Wait.. this doesn't make sense. The timekeeper lock is only for reading.
>
> What I was suggesting to you off line is to have something that avoids
> spinning on the seqcounter should if a bug occurs and we IPI all the
> cpus, that we don't deadlock or block any printk messages.
We could also extend the fast timekeeper with boot/real/tai extensions and use
that for printk. You can use ktime_get_mono_fast_ns() today.
Thanks,
tglx
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