Date: Tue, 24 Dec 2002 06:09:30 -0800 From: "Paul A. Scott" <pscott@skycoast.us> To: Poul-Henning Kamp <phk@freebsd.org>, <current@freebsd.org> Subject: Re: revoke(2) redux... Message-ID: <BA2DAA9A.17D62%pscott@skycoast.us> In-Reply-To: <30917.1040730025@critter.freebsd.dk>
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> From: Poul-Henning Kamp <phk@FreeBSD.ORG>
>>void setctty(char *name) {
>> (void) revoke(name);
>> if ((fd = open(name, O_RDWR)) == -1) {
> Isn't there a pretty obvious race between the revoke() and the open() ?
> Wouldn't it in fact make much more sense if revoke(2) was defined as
> int revoke(int fd); /* kick everybody else off */
> and the code above would look like:
>> if ((fd = open(name, O_RDWR)) == -1) {
>> }
>> (void) revoke(fd);
But, revoke() invalidates all descriptors for the named path, so any
subsequent operations on the open file descriptor would fail, which defeats
the purpose of open(). I think what's needed is some form of serialization
around revoke() and open(). I'm not a master of the init code, but it may be
that the code is inherently non-reentrant, so the original code would then
be okay.
Paul
Paul A. Scott
mailto:pscott@skycoast.us
http://skycoast.us/pscott/
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