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 82250C4361B for ; Sat, 19 Dec 2020 10:59:44 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1C23822288 for ; Sat, 19 Dec 2020 10:59:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1C23822288 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 5DB2D6B006C; Sat, 19 Dec 2020 05:59:43 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 564FF6B0070; Sat, 19 Dec 2020 05:59:43 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4536F6B0071; Sat, 19 Dec 2020 05:59:43 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0218.hostedemail.com [216.40.44.218]) by kanga.kvack.org (Postfix) with ESMTP id 2A8126B006C for ; Sat, 19 Dec 2020 05:59:43 -0500 (EST) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id CBD78181AF5C3 for ; Sat, 19 Dec 2020 10:59:42 +0000 (UTC) X-FDA: 77609736204.22.head96_5f14ee627445 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin22.hostedemail.com (Postfix) with ESMTP id AE9AA18038E73 for ; Sat, 19 Dec 2020 10:59:42 +0000 (UTC) X-HE-Tag: head96_5f14ee627445 X-Filterd-Recvd-Size: 3984 Received: from mout.gmx.net (mout.gmx.net [212.227.15.15]) by imf12.hostedemail.com (Postfix) with ESMTP for ; Sat, 19 Dec 2020 10:59:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gmx.net; s=badeba3b8450; t=1608375575; bh=Sm0KEeivfCSGkhYBFSQzrl+3S9zeurR5ZEKJwy/t8Ko=; h=X-UI-Sender-Class:Subject:From:To:Cc:Date:In-Reply-To:References; b=IEubuhqKOH9ZJITg1BsZEBkQ3DH0ICHmRQv+6p06lbFPWYmbQ3GaZ0cKMtJz2g0jI akc0o/o7AsX9zEHsXB4LJOPOhvRb1cd5s/ICsTSr5teEADXMfFOwj96NZFVk3xPCrD eBP8qF9wYx6C0w3f9r/5r6JBNPXXHNyeeLxMkUl0= 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 1M3lc9-1kqr4e08ix-000pe6; Sat, 19 Dec 2020 11:59:35 +0100 Message-ID: <18669bd607ae9efbf4e00e36532c7aa167d0fa12.camel@gmx.de> 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 Date: Sat, 19 Dec 2020 11:59:33 +0100 In-Reply-To: References: <6946d6e798866276f0d635f219cdd4ad05156351.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:H1qM+XieyYJ5XxGNZGXLrMgGY6KxifsgBXFl13LTsezN16W1G3D LVcrl/BpSxi4JEgkgWsF2tX8Q4LuuQhaP1jFMDz9XgaoaRcafM/8aA8k0U7140dA/Vuz9ED w2RN4bUCqyAY5xG0q5RFYwt+g5SMQyFvfJ26wyxb//+/90kfvVr1dwAb22OgtNeNFtJvmMb 5lYm6sRNCewl2mZEDGCjA== X-UI-Out-Filterresults: notjunk:1;V03:K0:u0vBkrP4qEM=:l/AkobQXgw0LIW6hNsnSp0 JgODlteCnls/7zCxzc3+Dvc1kugVRFV4TqUCAjDPRGSz7mivIQKpUtN9PmTp2OPzveHA8G7uK zO2dQalru9WE+8EdAbBczE7GuMu/5JoMez40nh8bV31fmrsbM4XpzLdhcG47gpKuD315f2ig0 3t6p0E42/LW93isf3RFfbuXUhbVyB9Fq9VrhgAwMr3yqDPtUFJsWd35e0ehdfhhZBsjiBEqWF wKpxblRtwjkvtKbY3+OzkS975boj15vCe/KZVaf9d4sjUr2MQbJ6AbHQS2SS9UttJy7xAo/yi IJ1X7p2EL9SeyFWm4z6Uw59+Klh9f7NhjX+wBIBfs9/BnBfkx2oY0EjwanhhaEOrsV12aYSXE mBCPIsIsir2l9A3E5Ke8xipMXPHlQbtEeEMRk6QXF3D5qA8hC2WV63aZdH74CJnLw3JPXKbix 7NjBLXD7LzwdaRm5J/M+zcjGw3cswVMJEqftew9KLtTyv1iCbDiyBtXnVdyhg2bPDcBQzea8C g4UWIaqlItyW2aKamtj7LDlNu5x7JdNfWtpM/U2IRSlOskqCcRuYJc6H1SwU54kxwAWXPHJCV il4gRD2nyR9EcVmRp2GzG1u+gJqbKgTx5e+ziU327uh+wo6dStjK/jy2dvYVpqcabH+HXB9Pw iZ4cLFfs8zGbWWVDsfgVxKwabhMIFkpY8QnzRAMC+dFHs1f2dYYL4yAayLG6hDbhfKFwzZJjJ 0g+QzXc44if5hju/tMvCriIKltGbzdAAXxRgelhYpSnpTH438ecT3QjXum9WGebLVZaYJNkMY KYJK12rkyhl+vXvmsW2S7MTLYgug7ZQnhbNJFb1i1pQmbJUDAedR5FIVzQdfdZsk7TVerh+rA TUwfJituVrZnruO+84yA== 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: 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 plai= n > > 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