I apologize if I give the impression of thinking I'm always right. I don't think I'm always right. In fact, I am frequently wrong.
What I do think is that in order to maintain the Plan 9 software, it would be helpful if I understood the problem and proposed solution before I start editing code. Too often when I don't fully understand what's going on, bugs end up going in with the fixes. There was a good instance of that over the weekend -- a subtle bug introduced into acme a few years ago (thanks to Arvindht Tamilmani for pointing it out). You pointed out a scenario where two processes can deadlock. That much I understood. There were two things I didn't understand. The first was how common the problem actually was. You made it sound like it happens all the time, and my understanding of the problem is that it shouldn't, hence my discussion of the usual file server conventions. You then said that rio+plumber was an example, which would certainly be a common case, except that as I understand the problem, rio+plumber doesn't suffer from it. Other cyclic dependency loops are even more common (as I understand them). Maybe your solution would fix those too. The second thing I didn't understand was what solution you propose. Saying "go do like Inferno does" isn't really helpful by itself. In just one or two sentences, you could explain the solution enough to know where in the Inferno kernel to look. I did look at cclose, pexit, and closefgrp in the Vita Nuova inferno, and I didn't see anything that looked significantly different from Plan 9. While writing this message, I checked the archived /usr/inferno trees on emelie and they looked the same too. I don't see anything there that would protect against the problem you described. Perhaps I'm looking in the wrong place, perhaps I don't understand what the code is doing, or perhaps I don't even understand what problem it is you were describing. I'm just trying to understand your suggestion. Thanks for your help. Russ
