From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754004Ab0ADTpJ (ORCPT ); Mon, 4 Jan 2010 14:45:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753737Ab0ADTpG (ORCPT ); Mon, 4 Jan 2010 14:45:06 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:55685 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753628Ab0ADTpG convert rfc822-to-8bit (ORCPT ); Mon, 4 Jan 2010 14:45:06 -0500 From: "Rafael J. Wysocki" To: Daniel Borkmann Subject: Re: [suspend/resume] Re: userspace notification from module Date: Mon, 4 Jan 2010 20:45:44 +0100 User-Agent: KMail/1.12.3 (Linux/2.6.33-rc2-tst; KDE/4.3.3; x86_64; ; ) Cc: =?iso-8859-2?q?Bart=B3omiej_Zimo=F1?= , linux-kernel@vger.kernel.org, awalls@radix.net, linux-pm@lists.linux-foundation.org, stern@rowland.harvard.edu References: <686edb2c.6263643a.4b3f4a3b.b60b3@o2.pl> <201001040045.39517.rjw@sisk.pl> <4B41E318.4050809@gmail.com> In-Reply-To: <4B41E318.4050809@gmail.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-2" Content-Transfer-Encoding: 8BIT Message-Id: <201001042045.44372.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday 04 January 2010, Daniel Borkmann wrote: > Rafael J. Wysocki wrote: > > On Monday 04 January 2010, Bartłomiej Zimoń wrote: > >> And what do You think about sending extra signals to processes? > > > > I don't see a problem with this in principle, although I don't think signals > > are very suitable for this particular purpose, because you need two-way > > communication between the power manager and the processes it's going to > > notify (because it has to wait for the processes to finish their preparations > > and to tell it that they are ready). > > Again, just to abandon some thoughts... do you really need that "two-way > communication"? I mean if the kernel delivers that specific signal to > the process/task_struct [do_signal():handle_signal()] it has to save the > original execution context that will later on be restored after the > non-default signal handling function returns. This is our ACK / > notification for the successful return of the programs "suspend > handler". The kernel module (if such exists) could be notified about > that for instance by a simple notifier hook within kernelspace. I mean > if I see this right, the "two-way" is just for the ACK isn't it? _If_ the kernel sends the signals, which is not I think should be done. Please keep that in the user space. Really. I don't see _any_ good reason for putting such things into the kernel. Rafael