From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E598CC4CECE for ; Mon, 14 Oct 2019 17:46:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4520320873 for ; Mon, 14 Oct 2019 17:46:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=freesources.org header.i=@freesources.org header.b="BIs+9bde" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729973AbfJNRqX (ORCPT ); Mon, 14 Oct 2019 13:46:23 -0400 Received: from mx3.freesources.org ([195.34.172.217]:37766 "EHLO mx3.freesources.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729776AbfJNRqX (ORCPT ); Mon, 14 Oct 2019 13:46:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=freesources.org; s=20160526; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:MIME-Version:Date:Message-ID:References:Cc:To:Subject:From; bh=dJfxNHNnlsUDn8K/FsMwSL5SjVmol/ntlIse2l79Gaw=; b=BIs+9bdeqx9T049n+iFRDDTsfpNGFBLSpiDOPPQPrx1w0+6AwjA76QOCvfqvArRkn31YTYvPmyHUZyf1/JKoHY4vyI3FOan5qDiJdLEXSwJNd4hoZIV5FXpAaYdKZmiYtRv5iyQ3xugUSDYD+xeB4yRVOROtoGqCu+wU37hue7U=; Received: from anon-34-247.vpn.ipredator.se ([46.246.34.247]) by mx3.freesources.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.84_2) (envelope-from ) id 1iK4QD-0004hT-JE; Mon, 14 Oct 2019 17:46:17 +0000 From: Jonas Meurer Subject: Re: [RFC PATCH] PM: Add a switch for disabling/enabling sync() before suspend To: "Rafael J. Wysocki" Cc: linux-pm@vger.kernel.org, Pavel Machek , Len Brown , Tim Dittler References: <56b2db6a-2f76-a6d3-662a-819cfb18d424@freesources.org> <2847488.TR0R5COpHM@kreacher> Openpgp: preference=signencrypt Autocrypt: addr=jonas@freesources.org; prefer-encrypt=mutual; keydata= mQINBEqFXAEBEAC+7gfLht8lDqGH1EPYoctDHvWQ4nk60UFDLfjqHmBGReL/9C7CyxYaqgY4 V1/DXPCmsO5PvHMSi6VPn3B81alPKMT6syQhxDN6CXETh/mrxRbTPyQVSKYdD/BvA94vgwfy iInR0N7K6J/mRxqKug14vXlABvfmyWBnW89d15OWs9qy1Ge1mHaA8UgIoUInR2mMqNHQf0nF /TtClN2uPmtv/GeGHfSSCQEjYq9Ih2Z1Re2hnwW1peEc0x7piKUXCXHGyrQdz5IE69SqV1gg vafUrWHNPWz5ZtXsihYioNi3ISuoHUjkKdn+t55en5tvWvi+2JQnMCGa/Wr7iA2EOxallR+z rQRBDe/6wp1XEz6vN1LqCeaRyVOR6q00PtN/Ot0tzPswrHKE6binqG6FBRbu+zeo87cNbMmH IAdIT3ysZCAwA2g310fBByCSiNnfhHg2GyqfC4eDtL/K7uVNqQQEon0yv8lzyUloofKER8eA W4PtahGcLLbREnekAwQMpU8y1a++QXdk1ckLoyGuBVpBX8PiRirzYVmYsGRMK2u0yIy73YYM gYpt6h+Vaoj5EyPbYuJRm3RItByzE84YBbKfA81Xn8FZWc2qTyTeKRMioTu37E/z46wSHCt9 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bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Hi Rafael and linux-pm maintainers, thanks a lot for your feedback, it's much appreciated! Rafael J. Wysocki: >> This patch adds a run-time switch at `/sys/power/suspend_sync`. > > I'd prefer "sync_on_suspend". Agreed and changed. >> The switch allows to enable or disable the final sync() from the suspend.= >> c >> Linux Kernel system suspend implementation. This is useful to avoid race >> conditions if block devices have been suspended before. Be aware that you= >> >> have to take care of sync() yourself before suspending the system if you >> disable it here. >> >> Since this is my first patch against the Linux kernel and I don't >> consider it ready for inclusion yet, I decided to send it to pm-linux >> and the PM subsystem maintainers only first. Would be very glad if you >> could take a look and comment on it :) >> >> Some questions: >> >> * There already is a build-time config flag[2] for en- or disabling the >> sync() in suspend.c. Is it acceptable to have both a build-time *and* >> a *run-time* switch? Or would a run-time switch have to replace the >> build-time switch? If so, a direct question to Rafael, as you added >> the build-time flag: Would that be ok for you? > > If there is a run-time knob to disable the syncing, the only reason for > the config option to be there will be to set the default value of that. Makes sense. I changed the meaning of the build-time flag accordingly. >> To give a bit more contect: In Debian, we're currently working[3] on >> support to suspend unlocked dm-crypt devices before system suspend. >> During that work, we realized that the final sync() from Linux Kernel >> system suspend implementation can lead to a dead lock. > > That's also true for FUSE filesystems I think and please note that this isn't > going to work with hibernation (in which case filesystems are synced > regardless). In my opinion, hibernation doesn't matter much. Since the memory is powered off on hibernation anyway, there's no reason to luksSuspend the devices beforehands, don't you think so? > The changes look reasonable to me. Glad to read. I'll send a second version of the patches as replies soon after this mail. How do we go on from here? Could you imagine to review them again and sign them afterwards? Or am I supposed to send them to the lkml and wait for feedback before getting more signers? As written, I'm new to the Linux Kernel development process and not sure what's the logical next step to get the patches merged. Thanks again for your help! Cheers jonas