Messages in this thread | | | Date | Wed, 6 Jan 2016 18:34:57 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH 1/2] kernel, timekeeping, add trylock option to ktime_get_with_offset() |
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On Wed, 6 Jan 2016, John Stultz wrote: > On Wed, Jan 6, 2016 at 5:00 AM, Prarit Bhargava <prarit@redhat.com> 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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