Have you seen resmgrd?
Keep in mind that I brought it as example of something that didn't quite catch up. And I did this to sort of emphasize the point that I don't believe in pure user-land solutions:-) I mean I kind of wanted to say "look, it kind of does the things you propose, yet, it did *not* really make it." And consequently "time is better spent adhering to block device even under 2.4, back-porting O_EXCL for block device[!], etc..."
For us programmers it would be nice to know the resmgr protocol and thus to get rid of forking an external program. (A study of resmgr client code should help.)
resmgr comes with libresmgr.so.1 with documented interface providing all the functionality exposed through command line directly to application. I far as I understand...
I believe this scheme is extensible enough for other operating systems.
As mentioned, the reality is rather that it's either "very portable" or "with explicit [and disjount] support for every system," because most of other system do provide means for serializing access and not using them is not an option. Cheers:-) A.