From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751221AbaAKVPZ (ORCPT ); Sat, 11 Jan 2014 16:15:25 -0500 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:58195 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750865AbaAKVPX (ORCPT ); Sat, 11 Jan 2014 16:15:23 -0500 Date: Sat, 11 Jan 2014 22:15:21 +0100 From: Pavel Machek To: Tejun Heo Cc: "Rafael J. Wysocki" , Alan Stern , Linus Torvalds , Kernel development list , linux-ide@vger.kernel.org, Linux-pm mailing list Subject: Re: No freezing of kernel threads (was: Re: [GIT PULL] libata fixes for v3.13-rc5) Message-ID: <20140111211521.GA12064@amd.pavel.ucw.cz> References: <1667032.A7Knz5cBng@vostro.rjw.lan> <20131226041856.GA16483@htj.dyndns.org> <1963765.T2MGFJrVrL@vostro.rjw.lan> <20131226160517.GB16483@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131226160517.GB16483@htj.dyndns.org> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > Well, it looks like we don't really know why things are done the way they > > are done at least in some cases, so in my personal view it would be good to > > go through all of the kernel freezer users just for this reason alone. We > > can't really say which of them are legitimate without that and how difficult > > it would be for them to switch over to using something more fine grained than > > the freezer. > > I'm a bit worried about things which may not be explicit. > ie. something which is broken but sorta working because things like > writeback and jbd are frozen. I think I worry about that because I > remember one argument for kernel freezer from way way back, that it's > too hard to implement proper suspend/resume for all drivers and by > freezing most kthreads things should mostly work, which sounded pretty > crazy to me even back then. Hopefully, we don't have much left > depending on such magic. Careful there. Hibernation depends on data on disk not changing after freeze. So you definitely do _not_ want writeback/jbd running while uswsusp does its image writing. (I wonder what happens if uswsusp needs to trigger writeback to free memory. But I'm too scared to check :-). Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html