From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753022AbcGMKdB (ORCPT ); Wed, 13 Jul 2016 06:33:01 -0400 Received: from mga14.intel.com ([192.55.52.115]:23417 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752749AbcGMKc5 (ORCPT ); Wed, 13 Jul 2016 06:32:57 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,356,1464678000"; d="scan'208";a="1020781554" From: Chen Yu To: Pavel Machek Cc: linux-pm@vger.kernel.org, "Rafael J. Wysocki" , Len Brown , linux-kernel@vger.kernel.org Subject: Re: [PATCH] PM / hibernate: Introduce snapshot test mode for hibernation References: <1467873658-31986-1-git-send-email-yu.c.chen@intel.com> <20160713095005.GA27870@amd> <578615D5.3060501@intel.com> <20160713102156.GA14505@atrey.karlin.mff.cuni.cz> Message-ID: <57861A70.9090606@intel.com> Date: Wed, 13 Jul 2016 18:39:44 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 MIME-Version: 1.0 In-Reply-To: <20160713102156.GA14505@atrey.karlin.mff.cuni.cz> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016年07月13日 18:21, Pavel Machek wrote: > Hi! > >> On 2016???07???13??? 17:50, Pavel Machek wrote: >>> On Thu 2016-07-07 14:40:58, Chen Yu wrote: >>>> This mode is to verify if the snapshot data written to >>>> swap device can be successfully restored to memory. It >>>> is useful to ease the debugging process on hibernation, >>>> since this mode can not only bypass the BIOSen/bootloader, >>>> but also the system re-initialization. >>>> >>>> For example: >>>> $ sudo echo snapshot > /sys/power/disk >>>> $ sudo echo disk > /sys/power/state >>>> >>>> /* manual resume.*/ >>>> $ sudo echo 8:3 > /sys/power/resume >>> Your examples will not work, will they? >> It works on my platform, although I did not tested it for too many >> rounds. > Please check again: > > sudo echo disk > /sys/power/state > -bash: /sys/power/state: Permission denied > > ...because bash does the open, not echo. Sorry, my bad, I logined as root:P I'll rewrite the commit log. >>> This is also quite tricky/dangerous. If you do this with filesystems >>> mounted R/W, it is "good bye, filesystems". >> Ah, yes, this is quite tricky, maybe we can use this option as a >> debug method, >> for example, boot with rootfs = initrd, without mounting any disks, >> and then swapon the swap device, and do a testing. This should be safer? > Yeah, that's the way. Read-only root is other option. > >>> I guess updating documentation would be welcome from my side, >>> otherwise it should be ok. >> OK, I'll update the documents. > Just add fat warning into the documentation. OK. > Thanks, > Pavel