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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 5F109C3F2CE for ; Wed, 4 Mar 2020 21:33:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2CDCA20828 for ; Wed, 4 Mar 2020 21:33:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388342AbgCDVdN (ORCPT ); Wed, 4 Mar 2020 16:33:13 -0500 Received: from mga17.intel.com ([192.55.52.151]:49685 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726440AbgCDVdN (ORCPT ); Wed, 4 Mar 2020 16:33:13 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Mar 2020 13:33:13 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,515,1574150400"; d="scan'208";a="263743798" Received: from rjwysock-mobl1.ger.corp.intel.com (HELO [10.249.153.168]) ([10.249.153.168]) by fmsmga004.fm.intel.com with ESMTP; 04 Mar 2020 13:33:11 -0800 Subject: Re: [PATCH v1] Revert "software node: Simplify software_node_release() function" To: Heikki Krogerus , Brendan Higgins Cc: gregkh@linuxfoundation.org, rafael@kernel.org, linux-kernel@vger.kernel.org, davidgow@google.com, Heidi Fahim , Hans de Goede References: <20200228000001.240428-1-brendanhiggins@google.com> <20200302135738.GD22243@kuha.fi.intel.com> From: "Rafael J. Wysocki" Organization: Intel Technology Poland Sp. z o. o., KRS 101882, ul. Slowackiego 173, 80-298 Gdansk Message-ID: Date: Wed, 4 Mar 2020 22:33:10 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200302135738.GD22243@kuha.fi.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/2/2020 2:57 PM, Heikki Krogerus wrote: > On Thu, Feb 27, 2020 at 04:00:01PM -0800, Brendan Higgins wrote: >> This reverts commit 3df85a1ae51f6b256982fe9d17c2dc5bfb4cc402. >> >> The reverted commit says "It's possible to release the node ID >> immediately when fwnode_remove_software_node() is called, no need to >> wait for software_node_release() with that." However, releasing the node >> ID before waiting for software_node_release() to be called causes the >> node ID to be released before the kobject and the underlying sysfs >> entry; this means there is a period of time where a sysfs entry exists >> that is associated with an unallocated node ID. >> >> Once consequence of this is that there is a race condition where it is >> possible to call fwnode_create_software_node() with no parent node >> specified (NULL) and have it fail with -EEXIST because the node ID that >> was assigned is still associated with a stale sysfs entry that hasn't >> been cleaned up yet. >> >> Although it is difficult to reproduce this race condition under normal >> conditions, it can be deterministically reproduced with the following >> minconfig on UML: >> >> CONFIG_KUNIT_DRIVER_PE_TEST=y >> CONFIG_DEBUG_KERNEL=y >> CONFIG_DEBUG_OBJECTS=y >> CONFIG_DEBUG_OBJECTS_TIMERS=y >> CONFIG_DEBUG_KOBJECT_RELEASE=y >> CONFIG_KUNIT=y >> >> Running the tests with this configuration causes the following failure: >> >> >> kobject: 'node0' ((____ptrval____)): kobject_release, parent (____ptrval____) (delayed 400) >> ok 1 - pe_test_uints >> sysfs: cannot create duplicate filename '/kernel/software_nodes/node0' >> CPU: 0 PID: 28 Comm: kunit_try_catch Not tainted 5.6.0-rc3-next-20200227 #14 >> >> kobject_add_internal failed for node0 with -EEXIST, don't try to register things with the same name in the same directory. >> kobject: 'node0' ((____ptrval____)): kobject_release, parent (____ptrval____) (delayed 100) >> # pe_test_uint_arrays: ASSERTION FAILED at drivers/base/test/property-entry-test.c:123 >> Expected node is not error, but is: -17 >> not ok 2 - pe_test_uint_arrays >> >> >> Reported-by: Heidi Fahim >> Signed-off-by: Brendan Higgins >> Cc: Heikki Krogerus >> Cc: Hans de Goede >> Cc: Rafael J. Wysocki > Reviewed-by: Heikki Krogerus > >> --- >> drivers/base/swnode.c | 14 +++++++------- >> 1 file changed, 7 insertions(+), 7 deletions(-) >> >> diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c >> index 0b081dee1e95c..de8d3543e8fe3 100644 >> --- a/drivers/base/swnode.c >> +++ b/drivers/base/swnode.c >> @@ -608,6 +608,13 @@ static void software_node_release(struct kobject *kobj) >> { >> struct swnode *swnode = kobj_to_swnode(kobj); >> >> + if (swnode->parent) { >> + ida_simple_remove(&swnode->parent->child_ids, swnode->id); >> + list_del(&swnode->entry); >> + } else { >> + ida_simple_remove(&swnode_root_ids, swnode->id); >> + } >> + >> if (swnode->allocated) { >> property_entries_free(swnode->node->properties); >> kfree(swnode->node); >> @@ -773,13 +780,6 @@ void fwnode_remove_software_node(struct fwnode_handle *fwnode) >> if (!swnode) >> return; >> >> - if (swnode->parent) { >> - ida_simple_remove(&swnode->parent->child_ids, swnode->id); >> - list_del(&swnode->entry); >> - } else { >> - ida_simple_remove(&swnode_root_ids, swnode->id); >> - } >> - >> kobject_put(&swnode->kobj); >> } >> EXPORT_SYMBOL_GPL(fwnode_remove_software_node); >> -- >> 2.25.1.481.gfbce0eb801-goog > thanks, > Patch applied as a fix for 5.6, thanks!