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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C855AEE49A8 for ; Mon, 21 Aug 2023 09:29:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234360AbjHUJ3b (ORCPT ); Mon, 21 Aug 2023 05:29:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55994 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234326AbjHUJ33 (ORCPT ); Mon, 21 Aug 2023 05:29:29 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 3D41291; Mon, 21 Aug 2023 02:29:28 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BA6F32F4; Mon, 21 Aug 2023 02:30:08 -0700 (PDT) Received: from [10.57.3.137] (unknown [10.57.3.137]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 07EC23F762; Mon, 21 Aug 2023 02:29:25 -0700 (PDT) Message-ID: <2f1beb3e-c9df-46c5-fe5d-0d688a730521@arm.com> Date: Mon, 21 Aug 2023 10:29:22 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:102.0) Gecko/20100101 Thunderbird/102.14.0 Subject: Re: [PATCH v5] perf: arm_cspmu: Separate Arm and vendor module Content-Language: en-GB To: Besar Wicaksono , Suzuki K Poulose Cc: "ilkka@os.amperecomputing.com" , "catalin.marinas@arm.com" , "will@kernel.org" , "mark.rutland@arm.com" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-tegra@vger.kernel.org" , Thierry Reding , Jonathan Hunter , Vikram Sethi , Richard Wiley , Eric Funsten References: <20230705104745.52255-1-bwicaksono@nvidia.com> From: Robin Murphy In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023-08-19 21:11, Besar Wicaksono wrote: [...] >>> +void arm_cspmu_impl_unregister(const struct arm_cspmu_impl_match >> *impl_match) >>> +{ >>> + struct device *dev; >>> + struct arm_cspmu_impl_match *match; >>> + >>> + match = arm_cspmu_impl_match_get(impl_match->pmiidr_val); >>> + >>> + WARN_ON(!match); Nit: do "if (WARN_ON(!match)) return;" rather than indenting almost the whole function. >>> + >>> + if (match) { >>> + /* Unbind the driver from all matching backend devices. */ >>> +dev_release: >>> + dev = driver_find_device(&arm_cspmu_driver.driver, NULL, >>> + match, arm_cspmu_match_device); >>> + if (dev) { >>> + device_release_driver(dev); >>> + goto dev_release; >>> + } >> >> minor nit: We could simply do : >> >> static int arm_cspmu_release_driver(struct device *dev, void *data) >> { >> struct arm_cspmu *cspmu = >> platform_get_drvdata(to_platform_device(dev)); >> >> if (cspmu && cspmu->impl.match == match) >> device_release_driver(dev); >> return 0; >> } >> >> ret = driver_for_each_device(&driver, NULL, match, >> arm_csmpu_release_driver); >> > > It doesn’t seem to work for me. > Is it safe to release while iterating via driver_for_each_device ? Looking at the klist code it doesn't *obviously* appear safe to modify the list during iteration, so probably best not to risk it anyway. However, please try to write this loop as an actual loop, e.g.: while ((dev = driver_find_device())) device_release_driver(); At first glance I thought there was a bug here that it's only processing a single device, then eventually I saw the goto and my thought changed to "Eww..." Thanks, Robin.