# Details of how Timers work?

**URL:** <https://forum.sierrawireless.com/t/details-of-how-timers-work/4865>\
**Category:** Open AT\
**Created:** [February 6, 2011, 10:24pm UTC](https://forum.sierrawireless.com/t/details-of-how-timers-work/4865 "2011-02-06T22:24:20Z")\
**Posts on this page:** 1\
**Showing post:** 3

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**Author:** ![awneil](https://avatars.discourse-cdn.com/v4/letter/a/49beb7/32.png) [@awneil](https://forum.sierrawireless.com/u/awneil)\
**Post date:** [February 23, 2011, 1:41pm UTC](https://forum.sierrawireless.com/t/details-of-how-timers-work/4865/3 "2011-02-23T13:41:58Z")

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> [@paruthiv](#):
>
> The timer events would be delayed if the applicative task is pre-empted due to higher priority (applicative or firmware) tasks processing.

I think the big question is: what happens if the handler takes so long that the same timer expires again before the handler has finished…

```auto
Start Periodic Timer
  |
  | timer 
  | running
  |
  +--expires--> Enter Handler
  | |
  | timer |handler
  | running |running
  | |for
  +--expires--> |a <<*** WHAT HAPPENS HERE??
  | |long
  | |time
```

See: [BUG: In the ongoing saga of timers, our hero boldly codes](https://forum.sierrawireless.com/t/bug-in-the-ongoing-saga-of-timers-our-hero-boldly-codes/4882/1)

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