In message <[EMAIL PROTECTED]>, "Paul A. Scott" writes: > >-- > >> From: Poul-Henning Kamp <[EMAIL PROTECTED]> >>>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 you missed the fine point in the "kick everybody *else* off" comment. >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. There is more code like this in places. The point is you cannot serialize against other processes. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message