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 na...@mips.inka.de
