possible bug in crond

Ralf Friedl Ralf.Friedl at online.de
Sun Jul 11 07:57:29 UTC 2010


Denys Vlasenko wrote:
> //FIXME: we will start a new job even if the old job is running
> //if crontab was reloaded: crond thinks that "new" job is different from "old"
> //even if they are in fact completely the same. Example
> //Crontab was:
> // 0-59 * * * job1
> // 0-59 * * * long_running_job2
> //User edits crontab to:
> // 0-59 * * * job1_updated
> // 0-59 * * * long_running_job2
> //Bug: crond can now start another long_running_job2 even if old one
> //is still running.
I didn't see any reference that cron is supposed to check whether the 
job is still running or not before starting a new one.
In fact, I tried this crtontab entry with the Vixie cron an my system
* * * * * sleep 10m
and the result after some time is
$ pstree | grep cron
├─cron───10*[cron───sleep]

It seems that busybox cron has some functionality that isn't even 
expected of cron.

Ralf


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