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From:   ebiederm@xmission.com (Eric W. Biederman)
To:     Christian Brauner <christian.brauner@canonical.com>
Cc:     Daniel Colascione <dancol@google.com>,
        Joel Fernandes <joelaf@google.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Tim Murray <timmurray@google.com>,
        Suren Baghdasaryan <surenb@google.com>
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Date:   Wed, 31 Oct 2018 00:00:51 -0500
In-Reply-To: <CAPP7u0X-FRgS0kGcL7dMEGzLys54UkXU3+drX76=NmMbCOLsxg@mail.gmail.com>
        (Christian Brauner's message of "Tue, 30 Oct 2018 12:19:51 +0100")
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Subject: Re: [RFC PATCH] Implement /proc/pid/kill
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Christian Brauner <christian.brauner@canonical.com> writes:

> On Tue, Oct 30, 2018 at 12:12 PM Daniel Colascione <dancol@google.com> wrote:
>>
>> On Tue, Oct 30, 2018 at 11:04 AM, Christian Brauner
>> <christian.brauner@canonical.com> wrote:
>> > On Tue, Oct 30, 2018 at 11:48 AM Daniel Colascione <dancol@google.com> wrote:
>> >>
>> >> Why not?
>> >>
>> >> Does your proposed API allow for a race-free pkill, with arbitrary
>> >> selection criteria? This capability is a good litmus test for fixing
>> >> the long-standing Unix process API issues.
>> >
>> > You'd have a handle on the process with an fd so yes, it would be.
>>
>> Thanks. That's good to hear.
>>
>> Any idea on the timetable for this proposal? I'm open to lots of
>> alternative technical approaches, but I don't want this capability to
>> languish for a long time.
>
> Latest end of year likely sooner depending on the feedback I'm getting
> during LPC.

Frankly.  If you want a race free fork variant probably the easiest
thing to do is to return a open copy of the proc directory entry.  Wrapped
in a bind mount so that you can't see beyond that directory in proc.

My only concern would be if a vfsmount per process would be too heavy for such a use.

Eric