Re: [9fans] Plan9 - the next 20 years

[roger peppe <rogpeppe@gmail.com>]

2009/4/21 erik quanstrom <quanstro@quanstro.net>:
>> i was trying to point out that if you try to
>> ignore the issue by removing flush from the
>> protocol, you'll get a system that doesn't work so smoothly.
>
> your failure cases seem to rely on poorly chosen tags.
> i wasn't suggesting that flush be eliminated.  i was
> thinking of ways of keeping flush self-contained.

my failure cases were based around supposing
that 9p messages could be re-ordered in transit,
as a response to maht's post.

they can't, so there's no problem, as far as i can see.

my proposal barely affects the flush semantics
(there'd be an additional rule that flushing a Tsequence
aborts the entire sequence, but i think that's it)

the race case that i was talking about cannot
be avoided by remembering old flushes. the
problem is that an action (which could involve any
number of irreversible side-effects) might have been
performed at the instant that you tell it to abort.
the semantics of flush let you know if you got there
in time to stop it.