linux-kernel - Re: [RFC] is_global_init() called on global init sub-thread

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Date:	Thu, 31 Dec 2015 19:08:23 -0600
From:	"Serge E. Hallyn" <serge.hallyn@...ntu.com>
To:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Richard Guy Briggs <rgb@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Serge E. Hallyn" <serge@...lyn.com>, linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [RFC] is_global_init() called on global init sub-thread

On Wed, Dec 30, 2015 at 03:25:42PM +0900, Sergey Senozhatsky wrote:
> Hello,
> 
> re-upping https://www.redhat.com/archives/linux-audit/2013-December/msg00086.html
> 
> Oleg Nesterov wrote:
> 
> :Because is_global_init() is only true for the main thread of /sbin/init.
> :
> :Just look at oom_unkillable_task(). It tries to not kill init. But, say,
> :select_bad_process() can happily find a sub-thread of is_global_init()
> :and still kill it.
> 
> this is still the case, isn't it? at least in some -stable kernels.
> is there (or was there) any reason this change has never been committed?
> (I'm particularly interested in is_global_init()).

...  seems like it makes sense.  Can you remind us which init you're having
to deal with?

>  static inline int is_global_init(struct task_struct *tsk)
>  {
> -	return tsk->pid == 1;
> +	return task_tgid_nr(tsk) == 1;
>  }
> 
> 	-ss
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