Many thanks.
[Very very sorry for late reply. I didn't notice to check Notify me option...and so I was not notified of the replies...
Now did.]
DOS is fine...
However I liked the exokernel approach given in the paper cited.
In Tenanbaum's book, he says eCos is such an OS.
To be honest, my question was little odd in constraining things a bit. By two thread actually I wanted to say, no system processes, that is, no active or running processes from OS or kernel should be present. If you see, in Linux, we have a lot of kernel threads running... that i wanted to avoid. The first three points which I said, actually describes all OSs. But my intention was to see an OS where only applications are active, that is, run as process, but OS is simply remains as passive one and almost dumb like a library...
Hope, I described my intention clearly...
But still, if I have constrained a bit more, kindly suggest or correct.
Regarding "disk access suffers due to lack of a system process taking care of caching of disk blocks"... Generally Linux or other OSs have a thread running to serve disk access...this process or thread's duty is to receive access request from user processes, serialize them, asynchronously access disk, cache the data, deliver the requested data to user process... I wanted this NOT to be there...no such process representing OS...true that without serializing disk requests and caching disk gets rotten faster, but just incase and OS are there with such an approach...
Sincerely,
Srinivas Nayak