9fans - fans of the OS Plan 9 from Bell Labs
 help / color / mirror / Atom feed
From: Anthony Martin <ality@pbrane.org>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Subject: Re: [9fans] Namespace inheritance between processes
Date: Sat, 21 May 2016 03:01:48 -0700	[thread overview]
Message-ID: <20160521100148.GA12547@dinah> (raw)
In-Reply-To: <CANLPe+O10qVKjd279LshD8PSCpUSQX3TQLyXzpVtMzbMdE975g@mail.gmail.com>

Casey Rodarmor <casey@rodarmor.com> once said:
> > Let's say I have a process A which forks a child process B with the
> > RFNAMEG so it receives a copy of A's namespace.
> >
> > If process A then makes a change to its namespace, will process B see
> > that change? Or does B receive a distinct copy that A then can't
> > change?

The latter. B won't observe any namespace changes made by A.

> Also, whatever the answer is, how can I test this for myself? I was
> struggling to come up with a combination of commands, short of writing
> some C programs, which would let me have two interactive rc shells
> that inherit from one another, since rc doesn't have job control and
> new rio windows are in a new process group.

In one rio window, do the following:

  % mkdir -p /tmp/wsys
  % mount $wsys /tmp/wsys 'new -r 0 0 512 512 -pid '$pid
  % { rc -i <>/tmp/wsys/cons >[1=0] >[2=0] } &

Any further changes to the namespace will be reflected in both windows.

Cheers,
  Anthony



  parent reply	other threads:[~2016-05-21 10:01 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-21  7:26 Casey Rodarmor
2016-05-21  7:37 ` Casey Rodarmor
2016-05-21  8:49   ` Skip Tavakkolian
2016-05-21 10:01   ` Anthony Martin [this message]
2016-05-21 12:06     ` Anthony Martin
2016-05-22  3:01       ` Casey Rodarmor
2016-05-22  5:28         ` Skip Tavakkolian
2016-05-22  6:14           ` erik quanstrom

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20160521100148.GA12547@dinah \
    --to=ality@pbrane.org \
    --cc=9fans@9fans.net \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).