Concurrency for grown-ups

Concurrency -- multi-processing -- is widely misunderstood. This article introduces the basic concurrency concepts you need to conduct your business in the server closets safely. Concurrency labels situations where more than one "application" is running at a time. Linux hosts always fill their process tables with a bunch of more-or-less simultaneous programs: network protocol daemons, cron managers, the kernel itself, and often much more. Linux is a multi-tasking operating system and it's built for this.