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ntpd: explain why scripts can be run in quick succession

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2010-01-25 19:30:16 +01:00
parent 3581c62515
commit 24928ffd8d
2 changed files with 24 additions and 9 deletions
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20
examples/var_service/ntpd/ntp.script
View File

@ -1,10 +1,12 @@
#!/bin/sh
exec 2>/dev/null
echo "`tail -n 99 "$0.log"`" >"$0.log"
exec >>"$0.log"
exec 2>&1
# Note that there is no provision to prevent several copies of the script
# to be run in quick succession. In fact, it happens rather often
# if initial syncronization results in a step.
# You will see "step" and then "stratum" script runs, sometimes
# as close as only 0.002 seconds apart.
#
# Script should be ready to deal with this.
dt=`date '+%Y-%m-%d %H:%M:%S'`
@ -13,17 +15,23 @@ if test x"$stratum" != x"" \
&& test 4 -ge "$stratum" \
&& test 128 -le "$poll_interval" \
; then
echo "`tail -n 199 -- "$0.log" 2>/dev/null`" >"$0.log.$$"
echo "$dt: $1"\
"freq_drift_ppm=$freq_drift_ppm"\
"offset=$offset"\
"stratum=$stratum"\
"poll_interval=$poll_interval,"\
"setting hardware clock"
"setting hardware clock"\
>>"$0.log.$$"
mv -- "$0.log.$$" "$0.log"
exec hwclock --systohc
fi
echo "`tail -n 199 -- "$0.log" 2>/dev/null`" >"$0.log.$$"
echo "$dt: $1"\
"freq_drift_ppm=$freq_drift_ppm"\
"offset=$offset"\
"stratum=$stratum"\
"poll_interval=$poll_interval"\
>>"$0.log.$$"
mv -- "$0.log.$$" "$0.log"

13
networking/ntpd.c
View File

@ -735,6 +735,13 @@ send_query_to_peer(peer_t *p)
}
/* Note that there is no provision to prevent several run_scripts
* to be done in quick succession. In fact, it happens rather often
* if initial syncronization results in a step.
* You will see "step" and then "stratum" script runs, sometimes
* as close as only 0.002 seconds apart.
* Script should be ready to deal with this.
*/
static void run_script(const char *action, double offset)
{
char *argv[3];
@ -1185,8 +1192,8 @@ update_local_clock(peer_t *p)
abs_offset = fabs(offset);
#if 0
/* If needed, -S script can detect this by looking at $offset
* env var and kill parent */
/* If needed, -S script can do it by looking at $offset
* env var and killing parent */
/* If the offset is too large, give up and go home */
if (abs_offset > PANIC_THRESHOLD) {
bb_error_msg_and_die("offset %f far too big, exiting", offset);
@ -2007,7 +2014,7 @@ int ntpd_main(int argc UNUSED_PARAM, char **argv)
nfds = poll(pfd, i, timeout * 1000);
gettime1900d(); /* sets G.cur_time */
if (nfds <= 0) {
if (G.cur_time - G.last_script_run > 11*60) {
if (G.script_name && G.cur_time - G.last_script_run > 11*60) {
/* Useful for updating battery-backed RTC and such */
run_script("periodic", G.last_update_offset);
gettime1900d(); /* sets G.cur_time */