Re: [PATCH 1/4] INIT_TASK() should initialize ->thread_group list

From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Cedric Le Goater <clg@vnet.ibm.com>,
	Dave Hansen <haveblue@us.ibm.com>,
	Eric Biederman <ebiederm@xmission.com>,
	Herbert Poetzl <herbert@13thfloor.at>,
	Ingo Molnar <mingo@elte.hu>,
	Mathias Krause <Mathias.Krause@secunet.com>,
	Roland McGrath <roland@redhat.com>,
	Serge Hallyn <serue@us.ibm.com>,
	Sukadev Bhattiprolu <sukadev@us.ibm.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/4] INIT_TASK() should initialize ->thread_group list
Date: Tue, 11 May 2010 19:15:37 -0700	[thread overview]
Message-ID: <20100512021537.GA11805@us.ibm.com> (raw)
In-Reply-To: <20100510194949.GB5249@redhat.com>

Oleg Nesterov [oleg@redhat.com] wrote:
| The trivial /sbin/init doing
| 
| 	int main(void)
| 	{
| 		kill(0, SIGKILL)
| 	}
| 
| crashes the kernel.

Really subtle. Good catch.

So, now init is not part of any process group until it calls setsid().
So the above SIGKILL is lost right ? - i.e it does not kill even init
itself.

In my quick test, the following init process lives on inspite of the
SIGKILL.

	main()
	{
		kill(0, SIGKILL);

		while(1)
			sleep(1); 
	}

I don't have a better solution. Maybe a hung init is better than a
crashed kernel. the patches look good.

Acked-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>