24928ffd8
Denys Vlasenko
2010-01-25
Subject
ntpd: explain why scripts can be run in quick succession
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examples/var_service/ntpd/ntp.script+14 -6
| @@ -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" |
networking/ntpd.c+10 -3
| @@ -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 */ | |