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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 4DE08C6778C for ; Fri, 6 Jul 2018 05:53:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0643B208D5 for ; Fri, 6 Jul 2018 05:53:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0643B208D5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=perches.com 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 S934766AbeGFFxD (ORCPT ); Fri, 6 Jul 2018 01:53:03 -0400 Received: from smtprelay0091.hostedemail.com ([216.40.44.91]:59728 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S934713AbeGFFw4 (ORCPT ); Fri, 6 Jul 2018 01:52:56 -0400 Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay07.hostedemail.com (Postfix) with ESMTP id 27645181D3368; Fri, 6 Jul 2018 05:52:55 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: joke35_366546ba7eb3b X-Filterd-Recvd-Size: 5433 Received: from XPS-9350.home (unknown [47.151.153.53]) (Authenticated sender: joe@perches.com) by omf10.hostedemail.com (Postfix) with ESMTPA; Fri, 6 Jul 2018 05:52:53 +0000 (UTC) Message-ID: Subject: Re: [PATCH] checkpatch: Add exceptions for dsb keyword usage From: Joe Perches To: Mark Rutland Cc: Prakruthi Deepak Heragu , apw@canonical.com, linux-arm-kernel , linux-kernel@vger.kernel.org, ckadabi@codeaurora.org, tsoni@codeaurora.org, bryanh@codeaurora.org Date: Thu, 05 Jul 2018 22:52:52 -0700 In-Reply-To: <20180706054510.puli24y6i6ylghxt@salmiak> References: <1530814776-16988-1-git-send-email-pheragu@codeaurora.org> <20180706054510.puli24y6i6ylghxt@salmiak> Content-Type: text/plain; charset="ISO-8859-1" X-Mailer: Evolution 3.28.1-2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2018-07-06 at 06:45 +0100, Mark Rutland wrote: > On Thu, Jul 05, 2018 at 02:14:28PM -0700, Joe Perches wrote: > > On Thu, 2018-07-05 at 11:19 -0700, Prakruthi Deepak Heragu wrote: > > > mb() API can relpace the dsb() API in the kernel code. So, dsb() usage > > > is discouraged. However, there are exceptions when dsb is used in a > > > variable or a function name. Exceptions are when 'dsb' is prefixed with > > > class [-_>*\.] and/or suffixed with class [-_\.;]. > > This is a really confusing way of describing the match behaviour, and doesn't > explain why this is a big problem. > > In C it's either: > > dsb() > dsb(scope) // e.g. dsb(ish) > > ... where scope is [a-z]*. > > ... which can be matched as something like 'dsb([a-z]*)' if necessary. > > > [] > > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl > > > > [] > > > @@ -5372,6 +5372,12 @@ sub process { > > > "Avoid line continuations in quoted strings\n" . $herecurr); > > > } > > > > > > +# dsb is too ARMish, and should usually be mb. > > > + if ($line =~ /[^-_>*\.]\bdsb\b[^-_\.;]/) { > > > + WARN("ARM_BARRIER", > > > + "Use of dsb is discouranged: prefer mb.\n" . > > > + $herecurr); > > > + } > > > > This patch is whitespace damaged with a spelling error. > > > > Also, if this is reasonable test, and I don't know > > that it is, it should be cc'd to the linux-arm list > > linux-arm-kernel@lists.infradead.org > > > > Also, I suggest 2 tests, one for .S files and > > another for .[ch] files, and this be made specific > > to arch/arm... files > > > > Something like: > > > > if ($realfile =~ @^arch/arm@ && > > ($realfile =~ /\.S$/ && $line =~ /\bdsb\b/) || > > ($realfile =~ /\.[ch]$/ && $line =~ /\bdsb\s*\(/)) { > > WARN("ARM_DSB", > > "Prefer mb over dsb as an ARM memory barrier\n" . $herecurr); > > } > > > > ARM people, is this reasonable? > > I don't think this is a big deal today. > > For code under arch/{arm,arm64}, it's perfectly reasonable to use dsb. > > For code *ouside* of arch/{arm,arm64}, there are a number of cases where we > want to use dsb(), e.g. when dealing with architectural drivers that require > special barriers, or for common code shared across arm and arm64. > > It doesn't look like this is a big problem today, anyhow: > > [mark@salmiak:~/src/linux]% git grep -w 'dsb(.*)' -- ^arch > drivers/irqchip/irq-armada-370-xp.c: dsb(); > drivers/irqchip/irq-gic-v3-its.c: dsb(ishst); > drivers/irqchip/irq-gic-v3-its.c: dsb(ishst); > drivers/irqchip/irq-gic-v3-its.c: dsb(sy); > drivers/irqchip/irq-gic-v3-its.c: dsb(sy); > drivers/irqchip/irq-gic-v3-its.c: dsb(sy); > drivers/mtd/nand/raw/cmx270_nand.c: dsb(); > drivers/mtd/nand/raw/cmx270_nand.c: dsb(); > drivers/mtd/nand/raw/cmx270_nand.c: dsb(); > drivers/mtd/nand/raw/cmx270_nand.c: dsb(); > drivers/mtd/nand/raw/cmx270_nand.c: dsb(); > drivers/perf/arm_spe_pmu.c: dsb(nsh); > drivers/perf/arm_spe_pmu.c: dsb(nsh); > drivers/power/reset/arm-versatile-reboot.c: dsb(); > drivers/soc/rockchip/pm_domains.c: dsb(sy); > drivers/soc/rockchip/pm_domains.c: dsb(sy); > drivers/staging/mt7621-mmc/sd.c: //dsb(); /* --- by chhung */ > drivers/staging/mt7621-mmc/sd.c: //dsb(); /* --- by chhung */ > drivers/staging/vc04_services/interface/vchiq_arm/vchiq.h:#define dsb(a) > drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c: dsb(sy); /* data barrier operation */ > drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c: dsb(sy); > drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.h: do { debug_ptr[DEBUG_ ## d] = __LINE__; dsb(sy); } while (0) > drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.h: do { debug_ptr[DEBUG_ ## d] = (v); dsb(sy); } while (0) > drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.h: do { debug_ptr[DEBUG_ ## d]++; dsb(sy); } while (0) > virt/kvm/arm/hyp/vgic-v3-sr.c: dsb(sy); > virt/kvm/arm/hyp/vgic-v3-sr.c: dsb(sy); > virt/kvm/arm/hyp/vgic-v3-sr.c: dsb(sy); Thanks Mark. So it seems this shouldn't be applied.