Re: [RFC][PATCH] new timeofday core subsystem (v. A3)

[Christoph Lameter]

On Fri, 11 Mar 2005, john stultz wrote:

> +/* get_lowres_timestamp():
> + *	Returns a low res timestamp.
> + *	(ie: the value of system_time as  calculated at
> + *	the last invocation of timeofday_periodic_hook() )
> + */
> +nsec_t get_lowres_timestamp(void)
> +{
> +	nsec_t ret;
> +	unsigned long seq;
> +	do {
> +		seq = read_seqbegin(&system_time_lock);
> +
> +		/* quickly grab system_time*/
> +		ret = system_time;
> +
> +	} while (read_seqretry(&system_time_lock, seq));
> +
> +	return ret;
> +}

On 64 bit platforms this could simply be a macro accessing "system time".

> +/* do_gettimeofday():
> + *	Returns the time of day
> + */
> +void do_gettimeofday(struct timeval *tv)
> +{
> +	nsec_t wall, sys;
> +	unsigned long seq;
> +
> +	/* atomically read wall and sys time */
> +	do {
> +		seq = read_seqbegin(&system_time_lock);
> +
> +		wall = wall_time_offset;
> +		sys = __monotonic_clock();
> +
> +	} while (read_seqretry(&system_time_lock, seq));
> +
> +	/* add them and convert to timeval */
> +	*tv = ns2timeval(wall+sys);
> +}
> +EXPORT_SYMBOL(do_gettimeofday);

Good.

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