From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423387AbXDYWmf (ORCPT ); Wed, 25 Apr 2007 18:42:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1423391AbXDYWmf (ORCPT ); Wed, 25 Apr 2007 18:42:35 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:45071 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1423387AbXDYWme (ORCPT ); Wed, 25 Apr 2007 18:42:34 -0400 Date: Thu, 26 Apr 2007 00:42:16 +0200 From: Pavel Machek To: Linus Torvalds Cc: Kenneth Crudup , Nick Piggin , Mike Galbraith , linux-kernel@vger.kernel.org, Thomas Gleixner , Con Kolivas , suspend2-devel@lists.suspend2.net, Ingo Molnar , Andrew Morton , Arjan van de Ven Subject: Re: suspend2 merge (was Re: [Suspend2-devel] Re: CFS and suspend2: hang in atomic copy) Message-ID: <20070425224216.GI17387@elf.ucw.cz> References: <20070424212408.GD16457@elf.ucw.cz> <20070425072350.GA6866@ucw.cz> <20070425202741.GC17387@elf.ucw.cz> <20070425214420.GG17387@elf.ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.11+cvs20060126 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > Not the same... but they are still related. "freeze" (for atomic > > snapshot) is actually subset of "suspend"... freeze needs DMAs off and > > saved state, and you need DMAs off and saved state for "suspend". > > THEY HAVE ABSOLUTELY NOTHING IN COMMON! > > Nobody in their right mind thinks that "disable DMA" and "suspend" are > similar operations. > > > So it is actually correct to do "suspend" when you want "freeze"; it > > is just slow. That's why they only differ in parameter these days. > > It is *not* correct to "suspend" when you want "freeze". Example? > I don't understand how you can even *claim* something like that. > > Here's a trivial example: > - SCSI disk > > Tell me, what does "suspend" do, and what does "freeze" (snapshot) do? Suspend syncs caches/spins down. Freeze does not do anything. That's okay, I keep claiming "freeze" is subset of "suspend". Can you name device where that is not true? Remember we do suspend(PMSG_FREEZE) atomic snapshot resume() write snapshot. So if we do spin the scsi disk down, nothing really bad happens, we'll just spin it up. (So scsi disk is not example I want. Spining down scsi disk on freeze is slow and stupid, but it is not incorrect). Yes, If I'd knew what I know now, drivers would have suspend/freeze/thaw/resume methods. We probably still can do that change. Unfortunately, it needs driver authors to understand 4 hooks (not 2) and do the right thing. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html