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, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, 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 1C7C0C3279B for ; Fri, 6 Jul 2018 17:02:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B6A70216FC for ; Fri, 6 Jul 2018 17:02:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="CBAeFTST"; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="RIbboCWg" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B6A70216FC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=codeaurora.org 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 S933989AbeGFRCj (ORCPT ); Fri, 6 Jul 2018 13:02:39 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:48010 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933561AbeGFRCh (ORCPT ); Fri, 6 Jul 2018 13:02:37 -0400 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id AE5CE60BDD; Fri, 6 Jul 2018 17:02:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1530896556; bh=jYvs2pN30ASArQIna37Yzw2SQAMa95+fhtWlW4HZXg0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=CBAeFTST16Gae/XtBgMjVUoPNkgaDul9IKKV9ILYuFjLYzd0smYdyIBaZcFavPZrF iE1NBjgowfJDVuzuMpa2IUxZyr4yNhHcFs3BHCwjHboRVfKywlNwkW/L+2zeKrJfT/ KzmJL89ZdlmQ48nOLDb3tIEeEMSPWfd1158+dSTM= Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.codeaurora.org (Postfix) with ESMTP id 32C9060BF7; Fri, 6 Jul 2018 17:02:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1530896555; bh=jYvs2pN30ASArQIna37Yzw2SQAMa95+fhtWlW4HZXg0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=RIbboCWgiPsc60bnGKurNS/c5C2fF+Gr/CFGl4lktigqU0YOLf5ESrHWRDClP9b3S E7fHl97WRquIQZea+o0x1WCHizwd7Y162fJiSYG9DC9YUziEMATbu66DeO5w2BC4JD TGgTTzIoHIGBuNPOzjQYOzkz99y6quPdAtBAsefw= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Fri, 06 Jul 2018 10:02:35 -0700 From: pheragu@codeaurora.org To: Mark Rutland Cc: Joe Perches , apw@canonical.com, linux-arm-kernel , linux-kernel@vger.kernel.org, ckadabi@codeaurora.org, tsoni@codeaurora.org, bryanh@codeaurora.org Subject: Re: [PATCH] checkpatch: Add exceptions for dsb keyword usage In-Reply-To: <20180706054510.puli24y6i6ylghxt@salmiak> References: <1530814776-16988-1-git-send-email-pheragu@codeaurora.org> <20180706054510.puli24y6i6ylghxt@salmiak> Message-ID: X-Sender: pheragu@codeaurora.org User-Agent: Roundcube Webmail/1.2.5 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018-07-05 22:45, 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. Thanks Mark. I appreciate your feedback.