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Date: Sun, 15 Mar 2015 15:52:23 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Josh Triplett <josh@joshtriplett.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>, Ingo Molnar <mingo@redhat.com>,
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Subject: Re: [PATCH v2 5/7] clone4: Add a CLONE_AUTOREAP flag to
	automatically reap the child process
Message-ID: <20150315145223.GA21887@redhat.com>
References: <cover.1426376419.git.josh@joshtriplett.org> <6d002995485d446e659105f6931307f3e532ce89.1426376419.git.josh@joshtriplett.org>
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On 03/15, Josh Triplett wrote:
>
> Add a CLONE_AUTOREAP flag to request this behavior unconditionally,

Yes, CLONE_AUTOREAP is much better. And I agree (mostly) with that
we should rely on do_notify_parent().

Howver the patch still doesn't look right. First of all, ->autoreap
should be per-process, not per-thread. And there are ptrace/mt issues,
it seems. Just for example, we should avoid EXIT_TRACE if autoreap in
wait_task_zombie() even if we are going to re-notify parent.

Yes... and other problems with ptrace. So let me nack this patch for
the moment ;) But let me repeat that personally I agree with this
change "in general".

EXCEPT: do we really want SIGCHLD from the exiting child? I think we
do not. I won't really argue though, but this should be discussed and
documented. IIUC, with your patch it is still sent.

Josh, please give me some time to think and re-check, I'll write another
email next week. I am not sure this is really needed, but it seems to
me that we need the preparation patch to make this change clear/simple.

Oleg.