From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756720Ab3BJXYm (ORCPT ); Sun, 10 Feb 2013 18:24:42 -0500 Received: from hydra.sisk.pl ([212.160.235.94]:36915 "EHLO hydra.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755335Ab3BJXYk (ORCPT ); Sun, 10 Feb 2013 18:24:40 -0500 From: "Rafael J. Wysocki" To: Pavel Machek Cc: Miklos Szeredi , Goswin von Brederlow , Li Fei , len.brown@intel.com, mingo@redhat.com, peterz@infradead.org, biao.wang@intel.com, linux-pm@vger.kernel.org, fuse-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, chuansheng.liu@intel.com Subject: Re: Getting rid of freezer for suspend [was Re: [fuse-devel] [PATCH] fuse: make fuse daemon frozen along with kernel threads] Date: Mon, 11 Feb 2013 00:31:03 +0100 Message-ID: <2964781.rPUOipNRNb@vostro.rjw.lan> User-Agent: KMail/4.9.5 (Linux/3.8.0-rc7; KDE/4.9.5; x86_64; ; ) In-Reply-To: <20130210185504.GA17268@amd.pavel.ucw.cz> References: <1360113112.17267.1.camel@fli24-HP-Compaq-8100-Elite-CMT-PC> <3938124.8eafYb16IB@vostro.rjw.lan> <20130210185504.GA17268@amd.pavel.ucw.cz> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sunday, February 10, 2013 07:55:05 PM Pavel Machek wrote: > Hi! > > > > > > The whole memory shrinking we do for hibernation is now done by allocating > > > > > memory, so the freezer is not necessary for *that* and there's *zero* > > > > > difference between suspend and hibernation with respect to why the freezer is > > > > > used. > > > > > > > > Funny. Freezer was put there so that hibernation image was safe to > > > > write out. You need disk subsystems in workable state for hibernation. > > > > > > I'm not really sure what you're talking about. Why do you think the freezer is > > > necessary for that? > > Well, from freezer you need: > > 1) user process frozen. > > 2) essential locks _not_ held so that block devices are still functional. > > > > > mmap... what is problem with mmap? For suspend, memory is powered, so > > > > you can permit people changing it. > > > > > > Suppose mmap is used to make the registers of some device available to user > > > space. Yes, that can happen. > > "Don't do it, then". Yes, can happen, but hopefully is not too common > these days. [And... freezer doing 1) but not 2) would be enough to > handle that. Freezer doing 1) but not 2) would also be simpler...] Again, I'm not sure what you mean. Are you trying to say that it would be OK to freeze user space tasks in the D state? Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.