[ardour-users] ok, spoke too soon... major crash w/ 0.9beta16.1

[Joe Cooper]

Fernando Pablo Lopez-Lezcano wrote:
> On Tue, 2004-06-08 at 17:03, Joe Cooper wrote:
> 
>>derek holzer wrote:
>>
>>>Just when I was getting to love it, Ardour froze up and made the machine 
>>>totally unresponsive! Couldn't even ssh in to kill the process, had to 
>>>reboot.
>>
>>It's worth pointing out here that a user level application, like ardour, 
>>cannot bring down a system*. 
> 
> 
> Any user application running threads with realtime scheduling can bring
> down a system. That's the tradeoff of not having xruns...
> 
> 
>>Only a system level bug can do that (or 
>>hardware failure).  Ardour might tickle the bug, but if your system 
>>crashed or froze while running Ardour then the kernel has a bug. 
>>Possibly, since presumably you've never seen it outside of Ardour (or 
>>you wouldn't be blaming Ardour) it is in the sound card driver you are 
>>using.  Jack might also be to blame, since it usually runs with rt 
>>priority, needs special privileges, and seems to interact more closely 
>>with the kernel than most sound servers (I'm guessing--I don't know 
>>where the user/system line is in the alsa/jack stack).
> 
> 
> A thread running with realtime scheduling can completely hog the cpu of
> a running system if it does not return control (ie: no other process
> gets to run ever again). Jack has a watchdog timer designed to prevent
> such a thing from happening, I guess it is not perfect. 

I had no idea ardour inherited the realtime scheduling from Jack (at 
least, I've never run ardour explicitly rt, though I do run jack with 
rt).  Good to know.

That brings to mind the question: Does one have to explicitly run ardour 
with rt to get realtime scheduling in ardour, and if so, how?  Running 
jack with realtime scheduling is documented, but I don't recall ever 
seeing anything about ardour and rt.  Perhaps I simply misunderstand how 
tightly jack and ardour are coupled (this is not at all unlikely).