linux-kernel - Re: [PATCH] exit.c: call proc_exit_connector() after exit

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Date:	Sat, 15 Mar 2014 12:22:01 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	matt.helsley@...il.com, Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Evgeniy Polyakov <zbr@...emap.net>,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH] exit.c: call proc_exit_connector() after exit_state is set

On Sat, Mar 15, 2014 at 12:12 PM, Oleg Nesterov <oleg@...hat.com> wrote:
>
> So I think the patch is fine, but let me repeat:
>
>         I hope that someone
>         can confirm that netlink_broadcast() is safe even if release_task(current)
>         was already called, so that the caller has no pids, sighand, is not visible
>         via /proc/, etc.
>
> not that I expect this should not work, but still.

Ok. I think people use netlink_broadcast from irq context (well,
strictly speaking looks lik ebottom half) judging by the GFP_ATOMIC
users, so that had better work regardless.

> Yes... BTW, Guillaume, I forgot to mention that perhaps you can use
> signalfd(SIGCHLD) instead of connector, this is epoll-able too. SIGCHLD
> doesn't queue, so it can't tell you which child has exited, but WNOHANG
> should work.

Yeah, that sounds like a good approach if SIGCHLD is the only thing needed.

Anyway, I see that the patch is apparently in -mm, and I think your
netlink_broadcast issue should be fine, so things are moving along.
It's not like this is a new issue or even so much an outright "bug" as
a misfeature.

             Linus
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