Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Florian Weimer <fweimer@redhat.com>
To:     Suren Baghdasaryan <surenb@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@kernel.org>,
        Michal Hocko <mhocko@suse.com>,
        David Rientjes <rientjes@google.com>,
        Matthew Wilcox <willy@infradead.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Roman Gushchin <guro@fb.com>, Rik van Riel <riel@surriel.com>,
        Minchan Kim <minchan@kernel.org>,
        Christian Brauner <christian@brauner.io>,
        Christoph Hellwig <hch@infradead.org>,
        Oleg Nesterov <oleg@redhat.com>,
        David Hildenbrand <david@redhat.com>,
        Jann Horn <jannh@google.com>,
        Shakeel Butt <shakeelb@google.com>,
        Tim Murray <timmurray@google.com>,
        Linux API <linux-api@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        kernel-team <kernel-team@android.com>
Subject: Re: [PATCH 1/1] mm: introduce process_reap system call
References: <20210623192822.3072029-1-surenb@google.com>
        <87sg0qa22l.fsf@oldenburg.str.redhat.com>
        <CAJuCfpEWpvw+gW+NvBPOdGqUOEyucFoT8gdC2uk18dMBQFbhqw@mail.gmail.com>
Date:   Thu, 08 Jul 2021 07:40:58 +0200
In-Reply-To: <CAJuCfpEWpvw+gW+NvBPOdGqUOEyucFoT8gdC2uk18dMBQFbhqw@mail.gmail.com>
        (Suren Baghdasaryan's message of "Wed, 7 Jul 2021 14:07:15 -0700")
Message-ID: <87wnq1z7kl.fsf@oldenburg.str.redhat.com>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

* Suren Baghdasaryan:

> On Wed, Jul 7, 2021 at 2:47 AM Florian Weimer <fweimer@redhat.com> wrote:
>>
>> * Suren Baghdasaryan:
>>
>> > The API is as follows,
>> >
>> >           int process_reap(int pidfd, unsigned int flags);
>> >
>> >         DESCRIPTION
>> >           The process_reap() system call is used to free the memory of=
 a
>> >           dying process.
>> >
>> >           The pidfd selects the process referred to by the PID file
>> >           descriptor.
>> >           (See pidofd_open(2) for further information)
>> >
>> >           The flags argument is reserved for future use; currently, th=
is
>> >           argument must be specified as 0.
>> >
>> >         RETURN VALUE
>> >           On success, process_reap() returns 0. On error, -1 is return=
ed
>> >           and errno is set to indicate the error.
>>
>> I think the manual page should mention what it means for a process to be
>> =E2=80=9Cdying=E2=80=9D, and how to move a process to this state.
>
> Thanks for the suggestion, Florian! Would replacing "dying process"
> with "process which was sent a SIGKILL signal" be sufficient?

That explains very clearly the requirement, but it raises the question
why this isn't an si_code flag for rt_sigqueueinfo, reusing the existing
system call.

Thanks,
Florian