> Fixing this in cron would not ensure mutual exclusion in the cases where these scripts are called by other means, eg manual calls.
I think we shouldn't consider external calls as this is out of cron's scope. It would be the same as I would say flock doesn't ensure mutual exclusion too as there are no guaranteed mandantory locks in the Linux kernel. -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to cron in Ubuntu. https://bugs.launchpad.net/bugs/917231 Title: Mutual exclusion for cronjobs Status in “cron” package in Ubuntu: New Bug description: I'm using Ubuntu 12.04 dev with cron 3.0pl1-120ubuntu2. I encountered in the past a problem which can be solved with a new feature. Here is an example of the problem: 0 0 * * * root /usr/local/share/python/backup_to_media.py 0 0 1 * * root /usr/local/share/python/backup_to_internet.py These cronjobs do backup some data every day to a media and one time a month to the internet. The problem is on the first day of every month both backups are running at the same time. This can cause some problems like the backuped data to the internet is one day older as it should be or there are maybe exceptions because both jobs are accessing the files at the same time. Maybe there could be a priority column which controls this: 0 0 * * * root 0 /usr/local/share/python/backup_to_media.py 0 0 1 * * root 1 /usr/local/share/python/backup_to_internet.py The priority column ensures that jobs which are running at the same time are excuted sequentially (if the priority of every job is the same number we will have the current behaviour). On the first day of every month /usr/local/share/python/backup_to_media.py is executed first because it has a lower number and if it finishes /usr/local/share/python/backup_to_internet.py is executed. This would prevent complicated entries in the crontab or own complex mutual exclusion to solve this problem. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/cron/+bug/917231/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
