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

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Message-ID: <20100613152918.GA8024@redhat.com>
Date:	Sun, 13 Jun 2010 17:29:18 +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: Re: [PATCH 1/1] signals: introduce send_sigkill() helper

Andrew, please drop

	signals-introduce-send_sigkill-helper.patch

I am stupid.

On 06/10, Oleg Nesterov wrote:
>
> Cleanup, no functional changes.
>
> There are a lot of buggy SIGKILL users in kernel. For example, almost
> every force_sig(SIGKILL) is wrong. force_sig() is not safe, it assumes
> that the task has the valid ->sighand, and in general it should be used
> only for synchronous signals. send_sig(SIGKILL, p, 1) or
> send_xxx(SEND_SIG_FORCED/SEND_SIG_PRIV) is not right too but this is not
> immediately obvious.
>
> The only way to correctly send SIGKILL is send_sig_info(SEND_SIG_NOINFO)

No, SEND_SIG_NOINFO doesn't work too. Oh, can't understand what I was
thinking about. current is the random task, but send_signal() checks
if the caller is from-parent-ns.

> Note: we need more cleanups here, this is only the first change.

We need the cleanups first. Until then oom-killer has to use force_sig()
if we want to kill the SIGNAL_UNKILLABLE tasks too.

Oleg.

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