From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH 1/1] suspend: delete sys_sync() Date: Tue, 4 Aug 2015 21:54:47 +0200 Message-ID: <20150804195447.GA28564@amd> References: <4290667.ZqInAykFGS@vostro.rjw.lan> <1850836.6zSgANe26P@vostro.rjw.lan> <1436427171.2530.5.camel@suse.com> <5271193.sYRdkO0AkU@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:52405 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752294AbbHDTyu (ORCPT ); Tue, 4 Aug 2015 15:54:50 -0400 Content-Disposition: inline In-Reply-To: <5271193.sYRdkO0AkU@vostro.rjw.lan> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "Rafael J. Wysocki" Cc: Oliver Neukum , Dave Chinner , Henrique de Moraes Holschuh , Len Brown , Len Brown , One Thousand Gnomes , Alan Stern , "linux-kernel@vger.kernel.org" , Linux PM list On Fri 2015-07-10 01:22:55, Rafael J. Wysocki wrote: > On Thursday, July 09, 2015 09:32:51 AM Oliver Neukum wrote: > > On Thu, 2015-07-09 at 00:03 +0200, Rafael J. Wysocki wrote: > > > > > Nothing and I'm not discussing that (I've said that already at least once in > > > this thread). > > > > > > What I'm questioning is the "why" of calling sys_sync() from the kernel. > > > > That's strictly speaking two questions > > > > 1. Why do it in the kernel > > > > That is easy. It closes the window of a race condition. > > > > 2. Why do it at all > > > > In essence because the system becomes inactive. For example we say that > > data hits the disk after 30s maximum. We cannot meet such a limit unless > > we sync. > > Absolute deadlines are not guaranteed to be met at all in general when > system suspend is used, at least from the user space perspective, so the > above is quite a bit of an overstretch. Well, this particular deadline _was_ guaranteed before Len's patch, and it is useful one, too: "if notebook is not on, it is ok to pull the USB stick". Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html