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 5CFE9C4167D for ; Wed, 13 Dec 2023 18:03:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377618AbjLMSDJ (ORCPT ); Wed, 13 Dec 2023 13:03:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44416 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233600AbjLMSDH (ORCPT ); Wed, 13 Dec 2023 13:03:07 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id AACF593 for ; Wed, 13 Dec 2023 10:03:13 -0800 (PST) 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 3174BC15; Wed, 13 Dec 2023 10:03:59 -0800 (PST) Received: from [10.1.197.60] (eglon.cambridge.arm.com [10.1.197.60]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 990913F762; Wed, 13 Dec 2023 10:03:10 -0800 (PST) Message-ID: Date: Wed, 13 Dec 2023 18:03:04 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v7 02/24] x86/resctrl: kfree() rmid_ptrs from rdtgroup_exit() Content-Language: en-GB To: Reinette Chatre , x86@kernel.org, linux-kernel@vger.kernel.org Cc: Fenghua Yu , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , Babu Moger , shameerali.kolothum.thodi@huawei.com, D Scott Phillips OS , carl@os.amperecomputing.com, lcherian@marvell.com, bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com, baolin.wang@linux.alibaba.com, Jamie Iles , Xin Hao , peternewman@google.com, dfustini@baylibre.com, amitsinght@marvell.com References: <20231025180345.28061-1-james.morse@arm.com> <20231025180345.28061-3-james.morse@arm.com> <208c3ade-a8c3-41cc-b136-4ab9b7e938e5@intel.com> From: James Morse In-Reply-To: <208c3ade-a8c3-41cc-b136-4ab9b7e938e5@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Reinette On 09/11/2023 17:39, Reinette Chatre wrote: > Hi James, > > Subject refers to rdtgroup_exit() but the patch is actually changing > resctrl_exit(). I'll fix that, > On 10/25/2023 11:03 AM, James Morse wrote: >> rmid_ptrs[] is allocated from dom_data_init() but never free()d. >> >> While the exit text ends up in the linker script's DISCARD section, >> the direction of travel is for resctrl to be/have loadable modules. >> >> Add resctrl_exit_mon_l3_config() to cleanup any memory allocated >> by rdt_get_mon_l3_config(). > > To match what patch actually does it looks like this should rather be: > "Add resctrl_exit_mon_l3_config()" -> "Add resctrl_put_mon_l3_config()" > >> >> There is no reason to backport this to a stable kernel. [...] >> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c >> index 19e0681f0435..0056c9962a44 100644 >> --- a/arch/x86/kernel/cpu/resctrl/core.c >> +++ b/arch/x86/kernel/cpu/resctrl/core.c >> @@ -992,7 +992,13 @@ late_initcall(resctrl_late_init); >> >> static void __exit resctrl_exit(void) >> { >> + struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl; >> + >> cpuhp_remove_state(rdt_online); >> + >> + if (r->mon_capable) >> + rdt_put_mon_l3_config(r); >> + >> rdtgroup_exit(); >> } > > I expect cleanup to do the inverse of init. I do not know what was the > motivation for the rdtgroup_exit() to follow cpuhp_remove_state() This will invoke the hotplug callbacks, making it look to resctrl like all CPUs are offline. This means it is then impossible for rdtgroup_exit() to race with the hotplug notifiers. (if you could run this code...) > but I > was expecting this new cleanup to be done after rdtgroup_exit() to be inverse > of init. This cleanup is inserted in middle of two existing cleanup - could > you please elaborate how this location was chosen? rdtgroup_exit() does nothing with the resctrl structures, it removes sysfs and debugfs entries, and unregisters the filesystem. Hypothetically, you can't observe any effect of the rmid_ptrs array being freed as all the CPUs are offline and the overflow/limbo threads should have been cancelled. Once cpuhp_remove_state() has been called, this really doesn't matter. Thanks, James