cron task time and work time

[Alice-Thirty]

The cron task run (every 5s).
Assume the runTask function run 1 minute.
How does cron work?

It will generate the 11-12 multitask at 1 minute?
If it does, how to let it run 1 task until runTask finish?

 new CronJob(
    '*/5 * * * * *',
    runTask(),
    null,
    true);