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Added sensible handling of switch to and from daylight saving time

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for the jobs that fall into the disappearing or duplicated time
interval.

PR:		bin/24494
This commit is contained in:
Sergey Babkin 2001-01-20 21:28:16 +00:00
parent 3c0cec43e7
commit 08b2398e6d
3 changed files with 158 additions and 5 deletions
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27
usr.sbin/cron/cron/cron.8
View File

@ -68,6 +68,33 @@ need not be restarted whenever a crontab file is modified. Note that the
.Xr crontab 1
command updates the modtime of the spool directory whenever it changes a
crontab.
.Pp
If the time zone has daylight saving time which differs by one hour from
the standard time and the switch to and from daylight saving time occurs
at :00 minutes (as in most of Asia, Europe and North America) then these
time switches are handled specially by
.Nm cron .
The time zones with other variations of daylight saving time (such as with
30 minutes difference or switched at :30 minutes etc.) do not have such
support.
.Pp
In the supported time zones the jobs run during the switches to and
from daylinght saving time as
intuitively expected. If a job falls
into a time interval that disappears during the switch from
standard time to daylight saving time or is
duplicated during the reverse switch, then it's handled
in one of two ways. The jobs that run every hour work
as always, they skip the skipped hour or run in the added
hour as usual. But the jobs that run less frequently
are executed exactly once, they are not skipped nor
executed twice (unless cron is restarted or the user's
.Xr crontab 5
is changed during such a time interval). If an hour disappears
during the switch to daylight saving time, such jobs are
executed during the next hour at the first minute that is specified
for them in
.Xr crontab 5 .
.Sh SEE ALSO
.Xr crontab 1 ,
.Xr crontab 5

133
usr.sbin/cron/cron/cron.c
View File

@ -36,13 +36,15 @@ static void usage __P((void)),
run_reboot_jobs __P((cron_db *)),
cron_tick __P((cron_db *)),
cron_sync __P((void)),
cron_sleep __P((void)),
cron_sleep __P((cron_db *)),
cron_clean __P((cron_db *)),
#ifdef USE_SIGCHLD
sigchld_handler __P((int)),
#endif
sighup_handler __P((int)),
parse_args __P((int c, char *v[]));
static time_t last_time = 0;
static void
usage() {
@ -66,7 +68,6 @@ main(argc, argv)
char *argv[];
{
cron_db database;
ProgramName = argv[0];
#if defined(BSD)
@ -127,7 +128,7 @@ main(argc, argv)
# if DEBUGGING
/* if (!(DebugFlags & DTEST)) */
# endif /*DEBUGGING*/
cron_sleep();
cron_sleep(&database);
load_database(&database);
@ -164,6 +165,7 @@ static void
cron_tick(db)
cron_db *db;
{
static struct tm lasttm;
register struct tm *tm = localtime(&TargetTime);
register int minute, hour, dom, month, dow;
register user *u;
@ -180,6 +182,93 @@ cron_tick(db)
Debug(DSCH, ("[%d] tick(%d,%d,%d,%d,%d)\n",
getpid(), minute, hour, dom, month, dow))
/* check for the daylight saving time change
* we support only change by +-1 hour happening at :00 minutes,
* those living in more strange timezones are out of luck
*/
if (last_time != 0 && tm->tm_isdst != lasttm.tm_isdst
&& TargetTime > last_time /* exclude stepping back */) {
int prevhr, nexthr, runtime;
int lastmin, lasthour;
int trandom, tranmonth, trandow;
time_t diff; /* time difference in seconds */
lastmin = lasttm.tm_min -FIRST_MINUTE;
lasthour = lasttm.tm_hour -FIRST_HOUR;
prevhr = (hour + (HOUR_COUNT-1)) % HOUR_COUNT;
nexthr = (lasthour + 1) % HOUR_COUNT;
if ( lasttm.tm_isdst != 1 && tm->tm_isdst == 1 /* ST->DST */
&& prevhr == nexthr ) {
diff = ( (hour*MINUTE_COUNT + minute)
- (lasthour*MINUTE_COUNT + lastmin)
+ HOUR_COUNT*MINUTE_COUNT
) % (HOUR_COUNT*MINUTE_COUNT);
diff -= (TargetTime - last_time) / 60/*seconds*/;
if (diff != MINUTE_COUNT)
goto dstdone;
if (hour == 0) {
trandom = lasttm.tm_mday -FIRST_DOM;
tranmonth = lasttm.tm_mon +1 /* 0..11 -> 1..12 */ -FIRST_MONTH;
trandow = lasttm.tm_wday -FIRST_DOW;
} else {
trandom = dom;
tranmonth = month;
trandow = dow;
}
for (u = db->head; u != NULL; u = u->next) {
for (e = u->crontab; e != NULL; e = e->next) {
/* adjust only jobs less frequent than 1 hr */
if ( !bit_test(e->hour, prevhr)
|| bit_test(e->hour, lasthour)
|| bit_test(e->hour, hour) )
continue;
if ( bit_test(e->month, tranmonth)
&& ( ((e->flags & DOM_STAR) || (e->flags & DOW_STAR))
? (bit_test(e->dow,trandow) && bit_test(e->dom,trandom))
: (bit_test(e->dow,trandow) || bit_test(e->dom,trandom)) )
) {
bit_ffs(e->minute, MINUTE_COUNT, &runtime);
if(runtime >= 0) {
e->tmval = TargetTime + (runtime-minute)*60;
e->flags |= RUN_AT;
e->flags &= ~NOT_UNTIL;
}
}
}
}
} else if ( lasttm.tm_isdst == 1 && tm->tm_isdst != 1 /* DST->ST */
&& lasthour == hour ) {
diff = ( (lasthour*MINUTE_COUNT + lastmin)
- (hour*MINUTE_COUNT + minute)
+ HOUR_COUNT*MINUTE_COUNT
) % (HOUR_COUNT*MINUTE_COUNT);
diff += (TargetTime - last_time) / 60/*seconds*/;
if (diff != MINUTE_COUNT)
goto dstdone;
runtime = TargetTime + (MINUTE_COUNT - minute)*60;
for (u = db->head; u != NULL; u = u->next) {
for (e = u->crontab; e != NULL; e = e->next) {
/* adjust only jobs less frequent than 1 hr */
if ( !bit_test(e->hour, hour)
|| bit_test(e->hour, prevhr)
|| bit_test(e->hour, nexthr) )
continue;
e->tmval = runtime;
e->flags |= NOT_UNTIL;
e->flags &= ~RUN_AT;
}
}
}
}
dstdone:
/* the dom/dow situation is odd. '* * 1,15 * Sun' will run on the
* first and fifteenth AND every Sunday; '* * * * Sun' will run *only*
* on Sundays; '* * 1,15 * *' will run *only* the 1st and 15th. this
@ -191,7 +280,14 @@ cron_tick(db)
Debug(DSCH|DEXT, ("user [%s:%d:%d:...] cmd=\"%s\"\n",
env_get("LOGNAME", e->envp),
e->uid, e->gid, e->cmd))
if (bit_test(e->minute, minute)
if (e->flags & NOT_UNTIL) {
if (TargetTime >= e->tmval)
e->flags &= ~NOT_UNTIL;
else
continue;
}
if ( (e->flags & RUN_AT) && TargetTime == e->tmval
|| bit_test(e->minute, minute)
&& bit_test(e->hour, hour)
&& bit_test(e->month, month)
&& ( ((e->flags & DOM_STAR) || (e->flags & DOW_STAR))
@ -199,10 +295,14 @@ cron_tick(db)
: (bit_test(e->dow,dow) || bit_test(e->dom,dom))
)
) {
e->flags &= ~RUN_AT;
job_add(e, u);
}
}
}
last_time = TargetTime;
lasttm = *tm;
}
@ -226,7 +326,9 @@ cron_sync() {
static void
cron_sleep() {
cron_sleep(db)
cron_db *db;
{
int seconds_to_wait = 0;
/*
@ -241,6 +343,7 @@ cron_sleep() {
*/
if (seconds_to_wait < -600 || seconds_to_wait > 600) {
cron_clean(db);
cron_sync();
continue;
}
@ -265,6 +368,26 @@ cron_sleep() {
}
/* if the time was changed abruptly, clear the flags related
* to the daylight time switch handling to avoid strange effects
*/
static void
cron_clean(db)
cron_db *db;
{
user *u;
entry *e;
last_time = 0;
for (u = db->head; u != NULL; u = u->next) {
for (e = u->crontab; e != NULL; e = e->next) {
e->flags &= ~(RUN_AT|NOT_UNTIL);
}
}
}
#ifdef USE_SIGCHLD
static void
sigchld_handler(x) {

3
usr.sbin/cron/cron/cron.h
View File

@ -172,6 +172,9 @@ typedef struct _entry {
#define DOM_STAR 0x01
#define DOW_STAR 0x02
#define WHEN_REBOOT 0x04
#define RUN_AT 0x08
#define NOT_UNTIL 0x10
time_t tmval;
} entry;
/* the crontab database will be a list of the