mobi phil wrote: > it would "freeze" anything else, [...] > application would be very small, would just show a number, or would do fast > lookup in a database with phonenumber etc.
Chances are that it will deadlock if everything else is really frozen :-) Naw, I'm not sure what specific problem you want to solve, but this concept sounds very dubious to me. If you're concerned that some unreliable daemon is handling all the kernel events, then you could extend it such that the events you're particularly interested in get passed through your watchdog first. There are also some events the daemon won't/can't "steal" from you. You can make your watchdog very resistant to any upset. Root can still kill it, but little else would scratch it - no runaway process, no fork bomb, no out of memory condition. Once upon a long ago, I wrote a user-space watchdog to handle the forced shutdown (power-off) when pressing POWER for more than 8 seconds. This is quite similar to what you described. The code is here: http://svn.openmoko.org/developers/werner/neodog The function invulnerabilize in neodog.c is probably what you're looking for. It ignores most signals, locks all pages into physical memory (so OOM can't kill you), and sets the highest scheduling priority (so nothing can preempt or starve you). While debugging your main loop, it's a good idea no to call invulnerabilize, or every busy loop will hang your system. - Werner
