From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422943AbXDYW4p (ORCPT ); Wed, 25 Apr 2007 18:56:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422957AbXDYW4p (ORCPT ); Wed, 25 Apr 2007 18:56:45 -0400 Received: from smtp1.linux-foundation.org ([65.172.181.25]:53341 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422943AbXDYW4o (ORCPT ); Wed, 25 Apr 2007 18:56:44 -0400 Date: Wed, 25 Apr 2007 15:55:58 -0700 (PDT) From: Linus Torvalds To: Nigel Cunningham cc: Pavel Machek , 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) In-Reply-To: <1177540027.5025.87.camel@nigel.suspend2.net> Message-ID: References: <20070419070437.GA25211@elte.hu> <20070424202336.GC16503@elf.ucw.cz> <20070424212408.GD16457@elf.ucw.cz> <20070425072350.GA6866@ucw.cz> <20070425202741.GC17387@elf.ucw.cz> <20070425214420.GG17387@elf.ucw.cz> <1177540027.5025.87.camel@nigel.suspend2.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 26 Apr 2007, Nigel Cunningham wrote: > > > > And name *one* thing that have in common. > > Set/reset the scsi transaction id thingy? Hibernation didn't work with > SCSI for a long time precisely because that support was missing. And by "hibernation", you mean what? You mean "snapshot + shutdown", right? Think about it for five seconds, and then ask yourself: at which point in the "snapshot + shutdown" sequence would you actually tell a disk to shut down? If you said "snapshot", then you'd be *wrong*. That's my _point_. The snapshot() function should not (and MUST NOT) tell disks to shut down, because unlike suspend(), we're still going to _use_ those disks afterwards (why? To write out the snapshot image!). In other words, the act of creating a snapshot has *nothing* to do with suspend. Now, after you've created (and written out) the snapshot, what do you actually end up doing? That's right - you end up _shutting down_ the machine, and yes, as part of the _shutdown_ sequence you may actually end up doing a lot of the things that a suspend would do. But that's long *after* you've actually done the "snapshot" part, and has absolutely nothing to do with it. That's where I started: whole "suspend to disk" thing actually has _more_ to do with "shutdown" than with "suspend". Linus