Messages in this thread | | | From | Arnd Bergmann <> | Date | Thu, 13 Jun 2019 17:40:15 +0200 | Subject | Re: infinite loop in read_hpet from ktime_get_boot_fast_ns |
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On Thu, Jun 13, 2019 at 5:19 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote: > > Hey Arnd, Peter, > > On Wed, Jun 12, 2019 at 4:01 PM Arnd Bergmann <arnd@arndb.de> wrote: > > Documentation/core-api/timekeeping.rst describes the timekeeping > > interfaces. I think what you want here is ktime_get_coarse_boottime(). > > > > Note that "coarse" means "don't access the hardware clocksource" > > here, which is faster than "fast", but less accurate. > > > > This is updated as often as "jiffies_64", but is in nanosecond resolution > > and takes suspended time into account. > > Oh, thanks. Indeed ktime_get_coarse_boottime seems even better. It's > perhaps a bit slower, in that it has that seqlock, but that might give > better synchronization between CPUs as well.
A seqlock is a very cheap synchronization primitive, I would actually guess that this is faster than most implementations of sched_clock() that access a hardware register for reading the time.
Arnd
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