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=-0.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 383B7C4361B for ; Sat, 19 Dec 2020 11:03:29 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id AD51722288 for ; Sat, 19 Dec 2020 11:03:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AD51722288 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmx.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 16A016B006C; Sat, 19 Dec 2020 06:03:28 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 11AF76B006E; Sat, 19 Dec 2020 06:03:28 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EFD696B0070; Sat, 19 Dec 2020 06:03:27 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0215.hostedemail.com [216.40.44.215]) by kanga.kvack.org (Postfix) with ESMTP id D9C0D6B006C for ; Sat, 19 Dec 2020 06:03:27 -0500 (EST) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 9EADD8249980 for ; Sat, 19 Dec 2020 11:03:27 +0000 (UTC) X-FDA: 77609745654.23.vein03_1b004ef27445 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin23.hostedemail.com (Postfix) with ESMTP id 8150937604 for ; Sat, 19 Dec 2020 11:03:27 +0000 (UTC) X-HE-Tag: vein03_1b004ef27445 X-Filterd-Recvd-Size: 4229 Received: from mout.gmx.net (mout.gmx.net [212.227.15.18]) by imf16.hostedemail.com (Postfix) with ESMTP for ; Sat, 19 Dec 2020 11:03:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1608375795; bh=uaTSZXPs8mGAHc0wJE1STHCcZRQ5t+E6vV+WWhZAebk=; h=X-UI-Sender-Class:Subject:From:To:Cc:Date:In-Reply-To:References; b=cR7nkKavwmijyx4BJ00vCGzigaiElKbB9pE2DcPw5pb3JBESgItQvky0atF1g0Bbp XYhqAxQaEohmH7IAjf8ABIzmg5uGMqQsRC1DOg/NO1z6bWsNISmLRi1lusbicu0c9D eSobqJtJNZHsW5FSEg0BjSx3mOmmsVctAS4MjlzA= X-UI-Sender-Class: 01bb95c1-4bf8-414a-932a-4f6e2808ef9c Received: from homer.fritz.box ([185.221.150.14]) by mail.gmx.com (mrgmx004 [212.227.17.190]) with ESMTPSA (Nemesis) id 1MgvvT-1k9Eqc25u9-00hKm1; Sat, 19 Dec 2020 12:03:15 +0100 Message-ID: Subject: Re: [patch] zswap: fix zswap_frontswap_load() vs zsmalloc::map/unmap() might_sleep() splat From: Mike Galbraith To: Vitaly Wool Cc: LKML , linux-mm , Barry Song , Sebastian Andrzej Siewior , Minchan Kim , NitinGupta Date: Sat, 19 Dec 2020 12:03:14 +0100 In-Reply-To: <18669bd607ae9efbf4e00e36532c7aa167d0fa12.camel@gmx.de> References: <6946d6e798866276f0d635f219cdd4ad05156351.camel@gmx.de> <18669bd607ae9efbf4e00e36532c7aa167d0fa12.camel@gmx.de> Content-Type: text/plain; charset="ISO-8859-15" User-Agent: Evolution 3.34.4 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:YhFvjMraDVR9ltDT5vH8xP9kyiH2f5djoWRLwx0aZLWhutvbmOJ eX/GE67Yh+19DccKxUs7hUcgmDiFuj7NCkTlL9uIoUUyM71cXn8zTPlplsuX6koG305W1/z nb1zCDejpZX1ZtFJoA/+DQhX+7gzCHjK4TRvXqhiw3r4ds9WtmgN2ng99vNzKOHbC5EdE6I L2weALDg4e58oQnBMw4dQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:irEI8XB0D0Q=:/ndnBO/AGzTxrD7dvbvWdz 5KIdCI8nmZSmbclLJnU2wmF43788flc5nN+klDluzIwinZoQz92ZQN7k/9yddV2ylRuPMf00i z3VJqW7+fRrAo1vmPn9hIHJe2v+LKhOuCKTantFnGRAY63wjmqv/nT1iI1HNxQLiCN/EZzOfV 7/lnVOnP5Ww8BTKiWHt61Rc61ih2OP+XeCGH3gu7e4ez7MdyeyPqtglXEs+zX8ruF/ELrH/Ux wrcKWEfMFU8zfNiE5Ui2Z07YEbzlcKpDFnjSZ1wbB//rCc9u9ScGppO0HabxjSEu8d8cVH3SH yZ520CdRn+uY/9wlKrYw2ZhAsFp3ZrlfYnmIAnBMiY/OWWreCn1KZLk9u6F7KxbFtiHZzCFMY CZq5QEohpzvYUwxupJ7oZ2NbkAquY41Ek+/pC7QemqEM38thIfuFZFrcOqEfHRhxSaEI4Z1sG n7e5lyzEpBsQewQ/oiOpjyEZzUwiyJlaZzxQTaGmKfUhcus0/URf4JpGbsHNFy0pJ5s083Dpl 7nuSEHZ+VjtF2HtwTg0XQkbDBAguJ2nu/BPFOjII6bPQAUAFM6Py3S9/r4wlBQ4YD6g8eFbUu MjdIA2U7VPK3wsV4ZGYDy0uxFG5MYpjwrZq71lBrRXOxcHroNQkYwIcDuNd1r1WkOtpVyPVOA 3pMbWlvFO3JQpokLX8efLiyt9w8WT/hRkNuiDdyG4RBz6aSEWssd1YZKHc1LAJZ+YleVWL0Mj jemy0jqlhNSElW3kQkpn+TFm8czyUrnlhgEP9mPVtRn3k85RDUdpsabQ9sa7/4wuirEERdF9H WFyT0G5Tnhwzg7LFfBdOcbwCw979YzGJ3922C+rRNXougs6jsezMW7uxG9XrZJSBN+jLkEZ+e X/htdilUflyIi/5rd2YA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: (CC zsmalloc maintainers) On Sat, 2020-12-19 at 11:59 +0100, Mike Galbraith wrote: > On Sat, 2020-12-19 at 11:46 +0100, Vitaly Wool wrote: > > On Sat, 19 Dec 2020, 11:27 Mike Galbraith, wrote: > > > > > The kernel that generated that splat was NOT an RT kernel, it was pl= ain > > > master.today with a PREEMPT config. > > > > > > I see, thanks. I don't think it makes things better for zsmalloc > > though. From what I can see, the offending code is this: > > > > > /* From now on, migration cannot move the object */ > > > pin_tag(handle); > > > > Bit spinlock is taken in pin_tag(). I find the comment above somewhat > > misleading, why is it necessary to take a spinlock to prevent > > migration? I would guess an atomic flag should normally be enough. > > > > zswap is not broken here, it is zsmalloc that needs to be fixed. > > Cool, those damn bit spinlocks going away would be a case of happiness > for RT as well :) > > -Mike