Is Pi with X-window good enough control /wo watchdog timer

[lilzz]

I want to use the Pi as the control system but I don't want the system to hang. Some people use a watchdog timer to watch the Pi, if it doesn't respond, the watchdog would power reset the Pi.

If I use the Pi in X-window(GUI) which is multiple tasking, is the chance of the system being hang is pretty low? Yeah, one particular task maybe got hung but not the whole system in X-window environment right?

So, I guess I don't need a watchdog for that?

[jamesh]

It depends what hangs. If the Linux kernel hangs, then you need a watchdog. But I beleive that would be quite unlikely. In fact, hangs in general are unlikely given decently written software.

Note that X is multitasking because Linux itself is. X doesn't add multitasking, it just uses what is already there

[redhawk]

The only time I've ever crashed my Pi was using batteries, a wifi dongle and a 3 watt speaker amp running off the USB port instead of the battery pack USB port.
If you're using a main power supply then the Pi shouldn't hang, if it does then something is probably wrong with the PSU or your F3 polyfuse is going bad http://elinux.org/R-Pi_Troubleshooting# ... r_problems

Richard S.

[DougieLawson]

On a uni-processor with a looping task (no external calls) you've very little chance even with a watchdog if you get an un-interupptable process running. Those things need a hardware process to get control back (like the Linux magic keys).

With normal userspace programming the stuff that runs there spends lots of time waiting for i/o events (and even longer if there's a human involved). The detection of long running tasks is a lot easier, depending on whether the dispatcher is pre-emptive or reactive. With Raspbian it's built with the pre-emptive options set for both kernel (hey, that's new since I last built a kernel) and userspace so it's a very robust system.

The likelihood of triggering any watchdog for a userspace program is so small it's probably not worth the effort of setting one up.