Re: kfifo: possible weird violation of what should be invariant

[Roland Dreier]

 >   sure, the code seems to work, but allowing the internal values of a
 > kfifo to contain invalid values on a regular basis would seem to make
 > a mess of, say, tracing or debugging.  making sure that offset values
 > actually lie within their valid range would seem to be one of those
 > ASSERT() things that should always be true, should it not?  is there a
 > reason the design is like this?

Actually I believe having the values be free-running without clamping
them makes the code much simpler -- the reason being that you preserve
the invariant of "in" always being ahead of "out".  If you reduce the
pointers modulo the size, then you end up having a lot of code that has
two cases: one to handle "in > out", and one to handle "in < out because
in has wrapped and out hasn't yet".

 - R.
-- 
Roland Dreier  <rolandd@xxxxxxxxx>
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