linux-kernel - [PATCH 0/1] signals: introduce send

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Message-ID: <20100610005937.GA4727@redhat.com>
Date:	Thu, 10 Jun 2010 02:59:37 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Roland McGrath <roland@...hat.com>
Cc:	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	David Rientjes <rientjes@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Nick Piggin <npiggin@...e.de>,
	Minchan Kim <minchan.kim@...il.com>
Subject: [PATCH 0/1] signals: introduce send_sigkill() helper

On 06/08, Oleg Nesterov wrote:
>
> > @@ -399,7 +399,7 @@ static int __oom_kill_process(struct task_struct *p, struct mem_cgroup *mem)
> >  	p->rt.time_slice = HZ;
> >  	set_tsk_thread_flag(p, TIF_MEMDIE);
> >
> > -	force_sig(SIGKILL, p);
> > +	send_sig(SIGKILL, p, 1);
>
> This is not right, we need send_sig(SIGKILL, p, 0). Better yet,
> send_sig_info(SIGKILL, SEND_SIG_NOINFO). I think send_sig() should
> die.
>
> The reason is that si_fromuser() must be true, otherwise we can't kill
> the SIGNAL_UNKILLABLE (sub-namespace inits) tasks.
>
> Oh. This reminds me, we really need the trivial (but annoying) cleanups
> here. The usage of SEND_SIG_ constants is messy, and they should be
> renamed at least.
>
> And in fact, we need the new one which acts like SEND_SIG_FORCED but
> si_fromuser(). We do not want to allocate the memory when the caller
> is oom_kill or zap_pid_ns_processes().

I tried to make some simple cleanups right now, but this really needs
time and discussion.

So. If we are going to remove force_sig() in mm/oom_kill.c (and I think
we should), I'd like to add the trivial helper first.

Oleg.

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