linux-kernel - Re: pidfd design

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Message-ID: <20190320191935.GB76715@google.com>
Date:   Wed, 20 Mar 2019 15:19:35 -0400
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Christian Brauner <christian@...uner.io>
Cc:     Daniel Colascione <dancol@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sultan Alsawaf <sultan@...neltoast.com>,
        Tim Murray <timmurray@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:ANDROID DRIVERS" <devel@...verdev.osuosl.org>,
        linux-mm <linux-mm@...ck.org>,
        kernel-team <kernel-team@...roid.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Andy Lutomirski <luto@...capital.net>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: pidfd design

On Wed, Mar 20, 2019 at 07:51:57PM +0100, Christian Brauner wrote:
[snip]
> > > translate_pid() should just return you a pidfd. Having it return a pidfd
> > > and a status fd feels like stuffing too much functionality in there. If
> > > you're fine with it I'll finish prototyping what I had in mind. As I
> > > said in previous mails I'm already working on this.
> > 
> > translate_pid also needs to *accept* pidfds, at least optionally.
> > Unless you have a function from pidfd to pidfd, you race.
> 
> You're misunderstanding. Again, I said in my previous mails it should
> accept pidfds optionally as arguments, yes. But I don't want it to
> return the status fds that you previously wanted pidfd_wait() to return.
> I really want to see Joel's pidfd_wait() patchset and have more people
> review the actual code.

No problem, pidfd_wait is also fine with me and we can change it later to
translate_pid or something else if needed.

Agreed that lets get to some code writing now that (I hope) we are all on the
same page and discuss on actual code.

 - Joel