svn commit: r241576 - in head/usr.sbin/cron: cron crontab lib

[Garrett Cooper]

On Mon, Oct 15, 2012 at 1:44 PM, Ian Lepore
<freebsd at damnhippie.dyndns.org> wrote:
> On Mon, 2012-10-15 at 22:26 +0200, Pawel Jakub Dawidek wrote:
>> On Mon, Oct 15, 2012 at 08:21:50AM +0000, Maxim Sobolev wrote:
>> > Author: sobomax
>> > Date: Mon Oct 15 08:21:49 2012
>> > New Revision: 241576
>> > URL: http://svn.freebsd.org/changeset/base/241576
>> >
>> > Log:
>> >   Add per-second scheduling into the cron(8). Right now it's
>> >   only available via the new @every_second shortcut. ENOTIME to
>> >   implement crontab(5) format extensions to allow more flexible
>> >   scheduling.
>> >
>> >   In order to address some concerns expressed by Terry Lambert
>> >   while discussing the topic few years ago, about per-second cron
>> >   possibly causing some bad effects on /etc/crontab by stat()ing
>> >   it every second instead of every minute now (i.e. atime update),
>> >   only check that database needs to be reloaded on every 60-th
>> >   loop run. This should be close enough to the current behaviour.
>> >
>> >   Add "@every_minute" shortcut while I am here.
>>
>> Do I read the code correctly and the cron deamon will wake up every
>> second now even if @every_second is not used at all?
>
> It appears to, which I don't think is a bad thing at all.  But the way
> it waits is to wake up, do some work, and go back to sleep for an
> integer 1 second.  That will occasionally lead to a second in which no
> wakeup happens, as the "do some work" part always takes some fraction of
> a second.

    This is silly. It should be waking up at the lowest common
denominator of time quanta, not every second; this could be determined
via the crontab its managing.
Thanks,
-Garrett