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 87C23C0018C for ; Sat, 19 Dec 2020 11:01:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3EFB523443 for ; Sat, 19 Dec 2020 11:01:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726545AbgLSLBX (ORCPT ); Sat, 19 Dec 2020 06:01:23 -0500 Received: from mout.gmx.net ([212.227.15.15]:50979 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726442AbgLSLBW (ORCPT ); Sat, 19 Dec 2020 06:01:22 -0500 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== Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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