From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Neukum Subject: Re: [RFC] Implementation of SCSI dynamic power management Date: Wed, 9 Jan 2008 18:31:57 +0100 Message-ID: <200801091831.58240.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-out002.kontent.com ([81.88.40.216]:46241 "EHLO smtp-out002.kontent.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751575AbYAIRb3 (ORCPT ); Wed, 9 Jan 2008 12:31:29 -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 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. > What happens during normal system resume if a driver (not just USB!) > needs to allocate memory before the swap device has been resumed? I have no idea. I guess these code paths have a sync in the suspend path, so a lot of clean pages will be available. Regards Oliver