Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751350AbbGIW4d (ORCPT ); Thu, 9 Jul 2015 18:56:33 -0400 Received: from v094114.home.net.pl ([79.96.170.134]:62638 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1750866AbbGIW40 (ORCPT ); Thu, 9 Jul 2015 18:56:26 -0400 From: "Rafael J. Wysocki" To: Oliver Neukum Cc: Dave Chinner , Henrique de Moraes Holschuh , Len Brown , Len Brown , One Thousand Gnomes , Alan Stern , "linux-kernel@vger.kernel.org" , Linux PM list Subject: Re: [PATCH 1/1] suspend: delete sys_sync() Date: Fri, 10 Jul 2015 01:22:55 +0200 Message-ID: <5271193.sYRdkO0AkU@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.1.0-rc5+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <1436427171.2530.5.camel@suse.com> References: <4290667.ZqInAykFGS@vostro.rjw.lan> <1850836.6zSgANe26P@vostro.rjw.lan> <1436427171.2530.5.camel@suse.com> 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 Content-Length: 1492 Lines: 40 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. > There are additional issues, such as a system appearing inactive during > suspension and frankly the far greater likelihood of a crash. I prefer the Alan's point, to be honest: it's a tradeoff between some extra safety and some extra suspend overhead. Unfortunately, though, we don't have any numbers allowing us to estimate how much extra safety it provides and so to justify it quantitatively, so to speak. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/