Re: [9fans] P9p on Fedora 12

[Russ Cox <rsc@swtch.com>]

On Mon, Aug 30, 2010 at 7:22 PM, Charles Forsyth <forsyth@terzarima.net> wrote:
> in rcinputproc
>                s = setecho(sfd, 0);
>                if(write(rcfd, pair.s, pair.ns) < 0)
>                        threadexitsall(nil);
>                if(s)
>                        setecho(sfd, s);
>
> there's a race between setting echo off, writing to rcfd, resetting echo and
> the reader of the other side of rcfd. a sleep(1) before if(s) makes it less frequent
> because the reader gets to read the data in the right mode.
> i haven't really looked at what linux is doing that allows that,
> or what changed between revisions.
>
> it's not my observation, it was on a list or issue comment somewhere,
> presumably for p9p. i can't find the bookmark.

thanks for this.  sleep(1) helped only rarely,
sleep(10) helps most of the time.  unfortunately
then there's a race between the invoked program
turning off echo and 9term turning it back on.
so "sudo sh" is pretty likely to echo the password
with the sleep in there.

what a mess.

russ