ticks and jiffies start at zero. During boot in initclocks(), we
reset them:
/* sys/kern/kern_clock.c */
89 int ticks;
90 static int psdiv, pscnt; /* prof => stat divider */
91 int psratio; /* ratio: prof / stat */
92
93 volatile unsigned long jiffies; /* XXX Linux API for drm(4) */
94
95 /*
96 * Initialize clock frequencies and start both clocks running.
97 */
98 void
99 initclocks(void)
100 {
101 ticks = INT_MAX - (15 * 60 * hz);
102 jiffies = ULONG_MAX - (10 * 60 * hz);
103
104 /* [... ] */
The idea here (committed by dlg@) is sound. We reset ticks and
jiffies to near-rollover values to catch buggy code misusing them.
But! That jump from zero to whatever violates valid assumptions made
by correct code, too.
It would be better to just initialize ticks and jiffies to the
near-rollover values when we declare them. To do this we need to
move their declarations from sys/kern/kern_clock.c to sys/conf/param.c
where HZ is visible.
ok?
Index: kern/kern_clock.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_clock.c,v
retrieving revision 1.106
diff -u -p -r1.106 kern_clock.c
--- kern/kern_clock.c 4 Feb 2023 19:33:03 -0000 1.106
+++ kern/kern_clock.c 27 Feb 2023 22:55:24 -0000
@@ -86,21 +86,15 @@ int stathz;
int schedhz;
int profhz;
int profprocs;
-int ticks;
static int psdiv, pscnt; /* prof => stat divider */
int psratio; /* ratio: prof / stat */
-volatile unsigned long jiffies; /* XXX Linux API for drm(4) */
-
/*
* Initialize clock frequencies and start both clocks running.
*/
void
initclocks(void)
{
- ticks = INT_MAX - (15 * 60 * hz);
- jiffies = ULONG_MAX - (10 * 60 * hz);
-
/*
* Set divisors to 1 (normal case) and let the machine-specific
* code do its bit.
@@ -171,7 +165,8 @@ hardclock(struct clockframe *frame)
tc_ticktock();
ticks++;
- jiffies++;
+ extern volatile unsigned long jiffies;
+ jiffies++; /* XXX drm(4) */
/*
* Update the timeout wheel.
Index: conf/param.c
===================================================================
RCS file: /cvs/src/sys/conf/param.c,v
retrieving revision 1.47
diff -u -p -r1.47 param.c
--- conf/param.c 13 Apr 2022 10:08:10 -0000 1.47
+++ conf/param.c 27 Feb 2023 22:55:24 -0000
@@ -73,6 +73,8 @@
#define HZ 100
#endif
int hz = HZ;
+int ticks = INT_MAX - (15 * 60 * HZ);
+volatile unsigned long jiffies = ULONG_MAX - (10 * 60 * HZ); /* drm(4) */
int tick = 1000000 / HZ;
int tick_nsec = 1000000000 / HZ;
int utc_offset = 0;
