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Date:   Thu, 11 Apr 2019 16:20:06 -0400
From:   Joel Fernandes <joel@joelfernandes.org>
To:     Christian Brauner <christian@brauner.io>
Cc:     linux-kernel@vger.kernel.org, luto@amacapital.net,
        rostedt@goodmis.org, dancol@google.com, jannh@google.com,
        surenb@google.com, torvalds@linux-foundation.org,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Andrei Vagin <avagin@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Arnd Bergmann <arnd@arndb.de>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Kees Cook <keescook@chromium.org>,
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        Michal Hocko <mhocko@suse.com>, Nadav Amit <namit@vmware.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Serge Hallyn <serge@hallyn.com>, Shuah Khan <shuah@kernel.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Taehee Yoo <ap420073@gmail.com>, Tejun Heo <tj@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, kernel-team@android.com,
        Tycho Andersen <tycho@tycho.ws>
Subject: Re: [PATCH RFC 1/2] Add polling support to pidfd
Message-ID: <20190411202006.GA130334@google.com>
References: <20190411175043.31207-1-joel@joelfernandes.org>
 <20190411200059.GA75190@google.com>
 <DA36DE02-73C2-4C9E-9761-27B3EBC6FED2@brauner.io>
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On Thu, Apr 11, 2019 at 10:02:32PM +0200, Christian Brauner wrote:
> On April 11, 2019 10:00:59 PM GMT+02:00, Joel Fernandes <joel@joelfernandes.org> wrote:
> >On Thu, Apr 11, 2019 at 01:50:42PM -0400, Joel Fernandes (Google)
> >wrote:
> >> pidfd are /proc/pid directory file descriptors referring to a task
> >group
> >> leader. Android low memory killer (LMK) needs pidfd polling support
> >to
> >> replace code that currently checks for existence of /proc/pid for
> >> knowing a process that is signalled to be killed has died, which is
> >both
> >> racy and slow. The pidfd poll approach is race-free, and also allows
> >the
> >> LMK to do other things (such as by polling on other fds) while
> >awaiting
> >> the process being killed to die.
> >
> >It appears to me that the "pidfd" now will be an anon inode fd, and not
> >based
> >on /proc/, based on discussions with Linus. So I'll rework the patches
> >accordingly. However that is relatively independent of this patch so
> >this
> >version can also be reviewed before I send out the reworked version.
> 
> Thank you very much, Joel.
> I'm off this week and traveling but I'll try to give it a look asap.
> 
> Christian

Sounds great to me, thanks a lot Christian.

 - Joel