Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755049Ab1BHQqi (ORCPT ); Tue, 8 Feb 2011 11:46:38 -0500 Received: from iolanthe.rowland.org ([192.131.102.54]:60421 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754815Ab1BHQqh (ORCPT ); Tue, 8 Feb 2011 11:46:37 -0500 Date: Tue, 8 Feb 2011 11:46:37 -0500 (EST) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Ian Campbell cc: "Rafael J. Wysocki" , , , "SUZUKI, Kazuhiro" , LKML Subject: Re: [linux-pm] [PATCH 0/2] Fix hangup after creating checkpoint on Xen. In-Reply-To: <1297164178.9388.65.camel@zakaz.uk.xensource.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1572 Lines: 39 On Tue, 8 Feb 2011, Ian Campbell wrote: > The problem is that currently we have: > > dpm_suspend_start(PMSG_SUSPEND); > > dpm_suspend_noirq(PMSG_SUSPEND); > > sysdev_suspend(PMSG_SUSPEND); > /* suspend hypercall */ > sysdev_resume(); > > dpm_resume_noirq(PMSG_RESUME); > > dpm_resume_end(PMSG_RESUME); > > However the suspend hypercall can return a value indicating that the > suspend didn't actually happen (e.g. was cancelled). This is used e.g. > when checkpointing guests, because in that case you want the original > guest to continue. When the suspend didn't happen the drivers need to > recover differently from if it did. That is odd, and it is quite different from the intended design of the PM core. Drivers are supposed to put their devices into a known suspended state; then afterwards they put the devices back into an operational state. What happens while the devices are in the suspended state isn't supposed to matter -- the system transition can fail, but devices get treated exactly the same way as if it succeeded. Why do your drivers need to recover differently based on the success of the hypercall? Alan Stern -- 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/