From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Tue, 10 Feb 1998 08:59:14 +0000
From: forsyth@caldo.demon.co.uk forsyth@caldo.demon.co.uk
Subject: [9fans] create(2)/open(2) race for file creation
Topicbox-Message-UUID: 7243c4c8-eac8-11e9-9e20-41e7f4b1d025
Message-ID: <19980210085914.g8qCDhAM_Z1j5U9xfmXHOIDBn9aEEJamMct3IKZHvwY@z>

i'm not sure i follow this.

in order to simplify one application that
purportedly has unusual needs, it is proposed as a sensible action,
and even dignified by reference to `research', to rush to change
a fundamental interface for dozens of other programs
(more if you include the ones gdb hasn't seen).
even then i wasn't sure i could understand the timing restrictions accurately
that prevented use of CHEXCL -- it seemed the race was
built into that application more than the kernel! but i hadn't
time to pursue it this week.

it's even more surprising, because (if one were to accept the
underlying assumptions, which as yet i don't), gdb himself proposed
an alternative solution by a flag to open (or something)
that didn't require as much messing about, isolated the change
and allowed me to ignore the whole matter for the moment!

i recall a caustic comment made by a friend of mine when
someone from the CSRG included things such as `increasing dev_t to 64 bits'
on a 1987 slide describing `research' they were undertaking with Unix.
i'd concluded from that talk that clever people can still be tempted just
to prat about with trivial things, and even then without THINKING.

if i were truly exercised by its existence, i might consider removing the
race in the implementation of the system call (in port/chan.c).
in practice, i'd probably think a little bit about the implications
of that, and then decide against bothering to do even that.
in a distributed system with processes
concurrently creating and destroying names, especially in the presence
of union mounts (where it isn't possible in general to rendezvous at a shared
file server because there isn't guaranteed to be a unique one),
some form of name-race is a fact of life,
and one might as well look to other mechanisms for a solution
to general synchronisation problems.
it's not even worth a reference to the Race Relations Board.