linux-kernel - Re: [PATCH 0/2] Send a SIGCHLD to the init's pid namespace parent when reboot

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Message-ID: <4E4DA461.8030006@free.fr>
Date:	Fri, 19 Aug 2011 01:46:41 +0200
From:	Daniel Lezcano <daniel.lezcano@...e.fr>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	"Serge E. Hallyn" <serge@...lyn.com>, akpm@...ux-foundation.org,
	bonbons@...ux-vserver.org, containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] Send a SIGCHLD to the init's pid namespace parent
 when reboot

On 08/15/2011 04:47 PM, Oleg Nesterov wrote:
> On 08/14, Serge E. Hallyn wrote:
>> Quoting Oleg Nesterov (oleg@...hat.com):
>>> On 08/11, Daniel Lezcano wrote:
>>>> In the case of a VPS, when we shutdown/halt/reboot the container, the
>>>> reboot utility will invoke the sys_reboot syscall which has the bad
>>>> effect to reboot the host.
>>> Stupid question. Can't sys_reboot() simply kill init (and thus the whole
>>> pid_ns) in this case?
>> The goal is to be able to distinguish a request for reboot from shutdown.
>> If we just kill the init, then the parent of init (the container monitor)
>> cannot restart the container to emulate reboot.
> OK, thanks.
>
> What if init reports the reason it was killed?
>
> Ignoring LINUX_REBOOT_CMD_CAD_/etc, I mean, roughly,
>
> 	- add "int reboot_cmd" into struct pid_namespace
>
> 	- sys_reboot(cmd) does
>
> 		if (!global_namespace) {
> 			task_active_pid_ns(current)->reboot_cmd = cmd;
> 			sigkill_my_init();
> 		}

Hi Oleg,

what would be your advice to get rid of from_ancestor_ns which prevent
the signal to be delivered to the init process ?

Thanks
  -- Daniel
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