From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Neukum Subject: Re: [RFC] Implementation of SCSI dynamic power management Date: Thu, 10 Jan 2008 10:26:59 +0100 Message-ID: <200801101027.00269.oliver@neukum.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from smtp-out001.kontent.com ([81.88.40.215]:46400 "EHLO smtp-out001.kontent.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753836AbYAJJ0T (ORCPT ); Thu, 10 Jan 2008 04:26:19 -0500 In-Reply-To: Content-Disposition: inline Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Alan Stern Cc: SCSI development list , Linux-pm mailing list Am Mittwoch, 9. Januar 2008 21:36:20 schrieb Alan Stern: > On Wed, 9 Jan 2008, Oliver Neukum wrote: > > > Am Mittwoch, 9. Januar 2008 18:22:51 schrieb Alan Stern: > > > On Wed, 9 Jan 2008, Oliver Neukum wrote: > > > > > > > This has an interesting implication. As the storage driver can share > > > > a device with in principle any other usb driver, we must audit all usb > > > > drivers if we wish to adopt this patch. > > > > All a device's interfaces must be resumed when the storage interface > > > > is resumed. To resume a storage device no memory must be allocated > > > > because that could deadlock. > > > > > > Maybe people shouldn't enable autosuspend for their swap device... > > > > Good advice, but not sufficient to avoid this problem. The vm may write > > out normal dirty cached pages to scsi devices, which affects storage. > > For now, I think the best approach is "head-in-the-sand". There aren't > a lot of USB storage devices partnered with other functions at the > moment. Very well with exception of the hub driver. > But it might be a good idea for all USB drivers to use GFP_NOIO in > their resume pathways. Yes, we should make this a requirement for every driver henceforth changed to support autosuspend. Regards Oliver