On Mon, 27 Oct 2014, Heena Sirwani wrote:
> The following patch adds a function to return tv_sec portion of
> ktime_get_real_ts64() function in order to have a function that returns
> seconds as 64-bit integers instead of 32-bit integers to address the
> y2038 problem.
>
> The function is similar to get_seconds() function except that it
> includes read_seqcount_retry loop which is required for 32-bit
> architectures. This is because 32-bit machines cannot access 64-bit
> tk->xtime_sec variable atomically, requiring two 32-bit register loads.
>
> Signed-off-by: Heena Sirwani <heenasirw...@gmail.com>
> Reviewed-by: Arnd Bergmann <a...@arndb.de>
> ---
> Changes in v2:
> - Removed the local variable nsecs as it was not required.
>
> include/linux/timekeeping.h | 1 +
> kernel/time/timekeeping.c | 19 +++++++++++++++++++
> 2 files changed, 20 insertions(+)
>
> diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
> index 115d55e..91454de 100644
> --- a/include/linux/timekeeping.h
> +++ b/include/linux/timekeeping.h
> @@ -29,6 +29,7 @@ struct timespec get_monotonic_coarse(void);
> extern void getrawmonotonic(struct timespec *ts);
> extern void ktime_get_ts64(struct timespec64 *ts);
> extern time64_t ktime_get_seconds(void);
> +extern time64_t ktime_get_real_seconds(void);
>
> extern int __getnstimeofday64(struct timespec64 *tv);
> extern void getnstimeofday64(struct timespec64 *tv);
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> index 93fc596..c17c620 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -673,6 +673,25 @@ time64_t ktime_get_seconds(void)
> }
> EXPORT_SYMBOL_GPL(ktime_get_seconds);
>
> +time64_t ktime_get_real_seconds(void)
> +{
> + time64_t seconds;
> + struct timekeeper *tk = &tk_core.timekeeper;
> + unsigned int seq;
> +
> + if (IS_ENABLED(CONFIG_64BIT))
> + return tk->xtime_sec;
> +
> + do {
> + seq = read_seqcount_begin(&tk_core.seq);
> + seconds = tk->xtime_sec;
> +
> + } while (read_seqcount_retry(&tk_core.seq, seq));
> +
> + return seconds;
> +}
> +EXPORT_SYMBOL_GPL(ktime_get_real_seconds);
Nice and clean implementation! Though I wonder whether we should just
name it get_seconds64().
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/
