From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755508Ab2CXLBi (ORCPT ); Sat, 24 Mar 2012 07:01:38 -0400 Received: from mail-bk0-f46.google.com ([209.85.214.46]:46287 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754277Ab2CXLBh (ORCPT ); Sat, 24 Mar 2012 07:01:37 -0400 Date: Sat, 24 Mar 2012 15:00:24 +0400 From: Anton Vorontsov To: Andrew Morton Cc: Greg Kroah-Hartman , Oleg Nesterov , Alan Cox , linux-kernel@vger.kernel.org Subject: [PATCH] sysrq: Use SEND_SIG_FORCED instead of force_sig() Message-ID: <20120324110024.GA14067@lizard> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Change send_sig_all() to use do_send_sig_info(SEND_SIG_FORCED) instead of force_sig(SIGKILL). With the recent changes we do not need force_ to kill the CLONE_NEWPID tasks. And this is more correct. force_sig() can race with the exiting thread, while do_send_sig_info(group => true) kill the whole process. Some more notes from Oleg Nesterov: > Just one note. This change makes no difference for sysrq_handle_kill(). > But it obviously changes the behaviour sysrq_handle_term(). I think > this is fine, if you want to really kill the task which blocks/ignores > SIGTERM you can use sysrq_handle_kill(). > > Even ignoring the reasons why force_sig() is simply wrong here, > force_sig(SIGTERM) looks strange. The task won't be killed if it has > a handler, but SIG_IGN can't help. However if it has the handler > but blocks SIGTERM temporary (this is very common) it will be killed. Also, > force_sig() can't kill the process if the main thread has already > exited. IOW, it is trivial to create the process which can't be > killed by sysrq. So, this patch fixes the issue. Suggested-by: Oleg Nesterov Acked-by: Greg Kroah-Hartman Acked-by: Oleg Nesterov Signed-off-by: Anton Vorontsov --- The patch depends on a few Oleg's patches in -mm, so I believe this should be -mm material as well. drivers/tty/sysrq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index 8db9125..5ab8039 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -329,7 +329,7 @@ static void send_sig_all(int sig) if (is_global_init(p)) continue; - force_sig(sig, p); + do_send_sig_info(sig, SEND_SIG_FORCED, p, true); } read_unlock(&tasklist_lock); } -- 1.7.9.2