Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753963Ab0FHSoH (ORCPT ); Tue, 8 Jun 2010 14:44:07 -0400 Received: from mx1.redhat.com ([209.132.183.28]:65318 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752373Ab0FHSoE (ORCPT ); Tue, 8 Jun 2010 14:44:04 -0400 Date: Tue, 8 Jun 2010 20:41:44 +0200 From: Oleg Nesterov To: KOSAKI Motohiro Cc: "Luis Claudio R. Goncalves" , LKML , linux-mm , David Rientjes , Andrew Morton , KAMEZAWA Hiroyuki , Nick Piggin , Minchan Kim Subject: Re: [PATCH 08/10] oom: use send_sig() instead force_sig() Message-ID: <20100608184144.GA5914@redhat.com> References: <20100608204621.767A.A69D9226@jp.fujitsu.com> <20100608210000.7692.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100608210000.7692.A69D9226@jp.fujitsu.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1489 Lines: 43 On 06/08, KOSAKI Motohiro wrote: > > Oleg pointed out oom_kill.c has force_sig() abuse. force_sig() mean > ignore signal mask. but SIGKILL itself is not maskable. Yes. And we have other reasons to avoid force_sig(). It should be used only for synchronous signals. But, > @@ -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(). OK. I'll send the simple patch which adds the new helper with the comment. send_sigkill() or kernel_kill_task(), or do you see a better name? Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/