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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 01F0DC43382 for ; Thu, 27 Sep 2018 21:12:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8918B21571 for ; Thu, 27 Sep 2018 21:12:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=yahoo.ca header.i=@yahoo.ca header.b="UuuAsBUd" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8918B21571 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=yahoo.ca Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728016AbeI1Dcr (ORCPT ); Thu, 27 Sep 2018 23:32:47 -0400 Received: from sonic309-21.consmr.mail.gq1.yahoo.com ([98.137.65.147]:37556 "EHLO sonic309-21.consmr.mail.gq1.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727340AbeI1Dcr (ORCPT ); Thu, 27 Sep 2018 23:32:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.ca; s=s2048; t=1538082753; bh=keDMkEhzcD51A892wLdsvfwC5PK0PU9UdcNVrUpnll4=; h=To:From:In-Reply-To:Cc:References:Subject:Date:From:Subject; b=UuuAsBUds/E5NlDdLbxpi5d68SrrVBevYBND10zR+ikF2sCzGgs18QTWJJSVjTzW4J1T2UmDKk2QWJ98e0t1cnLHXi9P8gjfOZlbZepBGURD59xLG4z8yeUEctaE36JbETAE2I+veMRtm0WLoxNQ2jbBIo9FcOrYEu8Lp91eurmrVkn5mI7ER/P8IspCYZ0P9TbONIZ7ah0YblzlAXLEf3IqmqST4/kU3t0evXO0BlzlxFaYYyyFFEQggMMNAAiBfZvW20qqQfSQ2yDmv4eSyGxCt0yvGXvaIxUE41CagLf7xHSK702U4/jMIuoLsT/f1vLb6zLCI5BOFB7oXSSbFA== X-YMail-OSG: mz815SkVM1mVVVMjRd2X5Iq_ZJQLvQVHbYRedlEGy4IcDNjgUyOVRemfXDl_2sA Ad8rRbVQPzrDTykgI4URVIbGfPIbyGwbY1s7RmTd92tDp_fxZF3nO.CtUVrgKd58OIKUh4LAOV_C 4Z3zkUAoMcVufnuloAjJkXz9oqKPtLZlN22kKMlOY_OPZsCWkx4bgul6hDpV0V2jhhBkmlnfdjOw P7O_Ftplw9JX2vqqT6q702mRLVNN987LTvPr0zf0flF.jOU9eNyIjZwaZWshUieO3XEzYOZATg6s 40M2bJy8UQIW8lp5uGvmL4PHe_xi9EhaCnFM8TD9KnvLIONtB7ZppevyTsR1CP_pPjLAOMI0K8xg xX7prmApzeLpt0m8Cbb.aLnndyidUc.xXAoTYFHhXFgWX2J8aEEO.hyI8z14.Cnhr76M9x2YMUgI 28YjIA5aFQyf99rKTUV0iCsYyAXf8pe35XaBAFyHQaaippGtltnlXq04p0tNgh0eNuNrs4vcNvgj XJ17tlw8xumJx8sKSHTtmpQUxiwdp9O04mLJRqJWhHOQuaeWzk8pkgPdGgUR3j.2g4SjCbTq7RQt Q1olFiVlvtDf.vhegdk9eq7SUztIXQQ5W6RNpFJ8WYaR75BHQ7TzYO9xGweYojI261tnDBtuCdlC pHThq6jvZsO0JWer59q4aUCxjawysNklPNjnoPjdjlFLYd5cwcRRY9Jh7jWvwvf35uC8KRiXWGLV 7p_yz4oHK85dpa94w2HLSa98UGuS1_Esm7S08wOXJZc7WiL8.ASqKZwDqoU.Wy5NjYaKNIfbMfjk MguAZqE9IK5xc0zU_JJp2AOzLDfwzZniynOwmTs5BHWWHkY6C0Av.QVlQvFT7zyte7Dehv2Lo3MW 1RBk.96AK.0q7jcLbnZhrKgYRA23Vc2huApeo9toLkqZQB9wnMeNVAQua_UjvnglVU3NrIHPFUiq 0DnuRUsWlDPx23UAp5NpwfM8PHdgKgf9ommIYXxVQHJ7SOIMg1KqQKfcu7dXwSUsCq54SPsUEThT lKAzeyC2B Received: from sonic.gate.mail.ne1.yahoo.com by sonic309.consmr.mail.gq1.yahoo.com with HTTP; Thu, 27 Sep 2018 21:12:33 +0000 Received: from pink.alxu.ca (EHLO localhost) ([198.98.62.56]) by smtp430.mail.gq1.yahoo.com (Oath Hermes SMTP Server) with ESMTPA ID 4a3511c8987175a4c5587e660d0d6381; Thu, 27 Sep 2018 21:12:32 +0000 (UTC) Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable To: Dan Streetman From: Alex Xu In-Reply-To: Cc: Linux-MM , linux-kernel References: <1538079759.qxp8zh3nwh.astroid@alex-archsus.none> Message-ID: <153808275043.724.15980761008814866300@pink.alxu.ca> User-Agent: alot/0.7 Subject: Re: [PATCH] mm: fix z3fold warnings on CONFIG_SMP=n Date: Thu, 27 Sep 2018 21:12:30 +0000 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Dan Streetman (2018-09-27 20:41:21) > On Thu, Sep 27, 2018 at 4:27 PM Alex Xu (Hello71) wr= ote: > > > > Spinlocks are always lockable on UP systems, even if they were just > > locked. > = > i think it would be much better to just use either > assert_spin_locked() or just spin_is_locked(), instead of an #ifdef. > = I wrote a longer response and then learned about the WARN_ON_SMP macro, so I'll just use that instead. Original response below: I thought about using assert_spin_locked, but I wanted to keep the existing behavior, and it seems to make sense to try to lock the page if we forgot to lock it earlier? Maybe not though; I don't understand this code completely. I did write a version of z3fold_page_ensure_locked with "if (assert_spin_locked(...))" but not only did that look even worse, it doesn't even work, because assert_spin_locked is a statement on UP systems, not an expression. It might be worth adding a ensure_spin_locked function that does that though... spin_is_locked currently still always returns 0 "on CONFIG_SMP=3Dn builds with CONFIG_DEBUG_SPINLOCK=3Dn", so that would just return us to the same problem of checking CONFIG_SMP.