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

[Thomas Gleixner]

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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/