Re: [PATCH v5] timekeeping: Added a function to return tv_sec portion of ktime_get_ts64()

Thomas Gleixner
2014-10-25T18:48:53Z

On Sat, 25 Oct 2014, Heena Sirwani wrote:
> +time64_t ktime_get_seconds(void)
> +{
> + time64_t ts;
> + struct timekeeper *tk = &tk_core.timekeeper;
> + struct timespec64 tomono;
> + s32 nsec;
> + unsigned int seq;
> +
> + WARN_ON(timekeeping_suspended);
> +
> + do {
> + seq = read_seqcount_begin(&tk_core.seq);
> + ts = tk->xtime_sec;
> + nsec = (long)(tk->tkr.xtime_nsec >> tk->tkr.shift);
> + tomono = tk->wall_to_monotonic;
> +
> + } while (read_seqcount_retry(&tk_core.seq, seq));
> +
> + ts += tomono.tv_sec;
> + if (nsec + tomono.tv_nsec >= NSEC_PER_SEC)
> + ts += 1;
> + return ts;

I'd rather have an extra field in the timekeeper

u64 xtime_sec;
+ u64 ktime_sec;

and update this in tk_update_ktime_data() so the readout function
boils down to

time64_t ktime_get_seconds(void)
{
#if BITS_PER_LONG < 64
u64 sec;
int seq;

do {
seq = read_seqcount_begin(&tk_core.seq);
sec = tk->ktime_sec;
} while (read_seqcount_retry(&tk_core.seq, seq));

return sec;
#else
return tk->ktime_sec;
#endif
}

So 64bit can do w/o the seqcount and 32bit avoids all extra math, right?

Thanks,

tglx