OK
I don't care if there is better machinery or numbers, this is far better
than the current situation. We lost power in a DC a few months back and we
had machines come up with clocks off by values between 30 seconds and 45
minutes.
On 9 Nov 2015 8:04 am, "Christian Weisgerber" <[email protected]> wrote:
> I would like to sync the system time periodically back to the RTC.
>
> Currently we update the RTC
> (1) when the time is set with clock_settime() or settimeofday(), which
> never happens for a typical ntpd setup,
> (2) before suspend,
> (3) when the system is properly shut down.
>
> This means if a machine has been running for a few months and it
> loses power, it may come back up with the time, say, 200 seconds
> off because of RTC drift, and then your SixXS tunnel won't come up
> and you can no longer reach your home network on the last day of
> u2k15. For example.
>
> FreeBSD uses a period of 30 minutes. I have no idea what a good
> number would be so I went with that. (Maybe a prime number of
> seconds?) FreeBSD also has a sysctl knob to change the period,
> which is silly.
>
> The patch below, inspired by FreeBSD, "seems to work for me", but
> I don't really know what I'm doing and if it's okay to just use a
> timeout(9) like that. Do I need a task? Any locking? I'm also
> uncertain where to put the hook to kick off the initial timeout_add().
>
>
> Index: kern/init_main.c
> ===================================================================
> RCS file: /cvs/src/sys/kern/init_main.c,v
> retrieving revision 1.246
> diff -u -p -r1.246 init_main.c
> --- kern/init_main.c 8 Nov 2015 20:45:57 -0000 1.246
> +++ kern/init_main.c 8 Nov 2015 21:06:47 -0000
> @@ -118,6 +118,8 @@ struct sigacts sigacts0;
> struct process *initprocess;
> struct proc *reaperproc;
>
> +void start_periodic_resettodr(void);
> +
> extern struct user *proc0paddr;
>
> struct vnode *rootvp, *swapdev_vp;
> @@ -550,6 +552,8 @@ main(void *framep)
> #if !(defined(__m88k__) && defined(MULTIPROCESSOR)) /* XXX */
> pool_gc_pages(NULL);
> #endif
> +
> + start_periodic_resettodr();
>
> /*
> * proc0: nothing to do, back to sleep
> Index: kern/kern_time.c
> ===================================================================
> RCS file: /cvs/src/sys/kern/kern_time.c,v
> retrieving revision 1.95
> diff -u -p -r1.95 kern_time.c
> --- kern/kern_time.c 1 Nov 2015 19:03:33 -0000 1.95
> +++ kern/kern_time.c 8 Nov 2015 16:46:46 -0000
> @@ -41,6 +41,7 @@
> #include <sys/vnode.h>
> #include <sys/signalvar.h>
> #include <sys/pledge.h>
> +#include <sys/timeout.h>
> #include <sys/timetc.h>
>
> #include <sys/mount.h>
> @@ -792,3 +793,21 @@ ppsratecheck(struct timeval *lasttime, i
> return (rv);
> }
>
> +
> +#define RESETTODR_PERIOD 1800
> +
> +void periodic_resettodr(void *);
> +struct timeout resettodr_to = TIMEOUT_INITIALIZER(periodic_resettodr,
> NULL);
> +
> +void
> +periodic_resettodr(void *arg __unused)
> +{
> + resettodr();
> + timeout_add_sec(&resettodr_to, RESETTODR_PERIOD);
> +}
> +
> +void
> +start_periodic_resettodr(void)
> +{
> + timeout_add_sec(&resettodr_to, RESETTODR_PERIOD);
> +}
> --
> Christian "naddy" Weisgerber [email protected]
>
>
