linux-kernel - Re: [PATCH 1/1] mm: introduce process

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Message-ID: <87wnq1z7kl.fsf@oldenburg.str.redhat.com>
Date:   Thu, 08 Jul 2021 07:40:58 +0200
From:   Florian Weimer <fweimer@...hat.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Michal Hocko <mhocko@...e.com>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>, Rik van Riel <riel@...riel.com>,
        Minchan Kim <minchan@...nel.org>,
        Christian Brauner <christian@...uner.io>,
        Christoph Hellwig <hch@...radead.org>,
        Oleg Nesterov <oleg@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Jann Horn <jannh@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Tim Murray <timmurray@...gle.com>,
        Linux API <linux-api@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-team <kernel-team@...roid.com>
Subject: Re: [PATCH 1/1] mm: introduce process_reap system call

* Suren Baghdasaryan:

> On Wed, Jul 7, 2021 at 2:47 AM Florian Weimer <fweimer@...hat.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, this
>> >           argument must be specified as 0.
>> >
>> >         RETURN VALUE
>> >           On success, process_reap() returns 0. On error, -1 is returned
>> >           and errno is set to indicate the error.
>>
>> I think the manual page should mention what it means for a process to be
>> “dying”, 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