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=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 2C679C48BCF for ; Sat, 12 Jun 2021 11:10:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EC7DA61248 for ; Sat, 12 Jun 2021 11:10:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231171AbhFLLMq (ORCPT ); Sat, 12 Jun 2021 07:12:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:37688 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229584AbhFLLMp (ORCPT ); Sat, 12 Jun 2021 07:12:45 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4BB3261376; Sat, 12 Jun 2021 11:10:46 +0000 (UTC) Received: from [185.219.108.64] (helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1ls1XI-0079Gc-6h; Sat, 12 Jun 2021 12:10:44 +0100 Date: Sat, 12 Jun 2021 12:10:43 +0100 Message-ID: <87eed7tk24.wl-maz@kernel.org> From: Marc Zyngier To: Austin Kim Cc: james.morse@arm.com, alexandru.elisei@arm.com, suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, austin.kim@lge.com Subject: Re: [PATCH] KVM: arm64: vgic: declear local variable 'flags' before for loop starts In-Reply-To: <20210612110014.GA1211@raspberrypi> References: <20210612110014.GA1211@raspberrypi> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: austindh.kim@gmail.com, james.morse@arm.com, alexandru.elisei@arm.com, suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, austin.kim@lge.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 12 Jun 2021 12:00:14 +0100, Austin Kim wrote: > > From: Austin Kim > > Normally local variable 'flags' is defined out of for loop, > when 'flags' is used as the second parameter in a call to > spinlock_irq[save/restore] function. > > So it had better declear local variable 'flags' ahead of for loop. Why better? Reducing the scope of a variable is in general good practice. Do you see any material advantage in moving this variable out of the loop? Does the compiler generate better code? Thanks, M. -- Without deviation from the norm, progress is not possible.