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[23.128.96.18]) by mx.google.com with ESMTP id ho44si10260028ejc.535.2021.10.29.09.41.10; Fri, 29 Oct 2021 09:41:35 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=NZOj7X3I; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229623AbhJ2Qja (ORCPT + 99 others); Fri, 29 Oct 2021 12:39:30 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:56853 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229676AbhJ2Qj3 (ORCPT ); Fri, 29 Oct 2021 12:39:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1635525420; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=f0EKBqxFMa5cFoenII9BpUm91FFdFL/tse0ALEuoccU=; b=NZOj7X3IttocF5CkchfM0B2bhnja3GzZxG2mg98ekuVIgwwNAe9XfY9z5WcZXBPMn3uMxe i4JC3cDnrFjowPajFwAqCeE/rkPE3LrKXpqu9Gweg9EDU0iXL/uhljSq8QoLrOCXnwtbhu jtATZ+8yOIDgdeJvevV84r1yW562FRM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-366-U94BKAc4NhK_iiKio3fBBw-1; Fri, 29 Oct 2021 12:36:59 -0400 X-MC-Unique: U94BKAc4NhK_iiKio3fBBw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 393BB1006AA2; Fri, 29 Oct 2021 16:36:57 +0000 (UTC) Received: from T590 (ovpn-8-18.pek2.redhat.com [10.72.8.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 249835FC23; Fri, 29 Oct 2021 16:36:34 +0000 (UTC) Date: Sat, 30 Oct 2021 00:36:28 +0800 From: Ming Lei To: Joe Lawrence Cc: Josh Poimboeuf , Jiri Kosina , Miroslav Benes , Petr Mladek , live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Luis Chamberlain , ming.lei@redhat.com Subject: Re: [PATCH 0/3] livepatch: cleanup kpl_patch kobject release Message-ID: References: <20211028125734.3134176-1-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 29, 2021 at 09:51:54AM -0400, Joe Lawrence wrote: > On Thu, Oct 28, 2021 at 08:57:31PM +0800, Ming Lei wrote: > > Hello, > > > > The 1st patch moves module_put() to release handler of klp_patch > > kobject. > > > > The 2nd patch changes to free klp_patch and other kobjects without > > klp_mutex. > > > > The 3rd patch switches to synchronous kobject release for klp_patch. > > > > Hi Ming, > > I gave the patchset a spin on top of linus tree @ 1fc596a56b33 and ended > up with a stuck task: > > Test > ---- > Enable the livepatch selftests: > $ grep CONFIG_TEST_LIVEPATCH .config > CONFIG_TEST_LIVEPATCH=m > > Run a continuous kernel build in the background: > $ while (true); do make clean && make -j$(nproc); done > > While continuously executing the selftests: > $ while (true); do make -C tools/testing/selftests/livepatch/ run_tests; done > > Results > ------- Hello Joe, Thanks for the test! Can you replace the 3rd patch with the following one then running the test again? From 599e96f79aebc388ef3854134312c6039a7884bf Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Thu, 28 Oct 2021 20:11:23 +0800 Subject: [PATCH 3/3] livepatch: free klp_patch object synchronously klp_mutex isn't acquired before calling kobject_put(klp_patch), so it is fine to free klp_patch object synchronously. One issue is that enabled store() method, in which the klp_patch kobject itself is deleted & released. However, sysfs has provided APIs for dealing with this corner case, so use sysfs_break_active_protection() and sysfs_unbreak_active_protection() for releasing klp_patch kobject from enabled_store(). Signed-off-by: Ming Lei --- include/linux/livepatch.h | 1 - kernel/livepatch/core.c | 32 +++++++++++++------------------- kernel/livepatch/core.h | 2 +- kernel/livepatch/transition.c | 2 +- 4 files changed, 15 insertions(+), 22 deletions(-) diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index 9712818997c5..4dcebf52fac5 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h @@ -169,7 +169,6 @@ struct klp_patch { struct list_head obj_list; bool enabled; bool forced; - struct work_struct free_work; }; #define klp_for_each_object_static(patch, obj) \ diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 9ede093d699a..6cfc54f6bdcc 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -337,6 +337,7 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr, int ret; bool enabled; LIST_HEAD(to_free); + struct kernfs_node *kn = NULL; ret = kstrtobool(buf, &enabled); if (ret) @@ -369,7 +370,14 @@ static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr, out: mutex_unlock(&klp_mutex); - klp_free_patches_async(&to_free); + if (list_empty(&to_free)) { + kn = sysfs_break_active_protection(kobj, &attr->attr); + WARN_ON_ONCE(!kn); + sysfs_remove_file(kobj, &attr->attr); + klp_free_patches(&to_free); + if (kn) + sysfs_unbreak_active_protection(kn); + } if (ret) return ret; @@ -684,32 +692,19 @@ static void klp_free_patch_finish(struct klp_patch *patch) kobject_put(&patch->kobj); } -/* - * The livepatch might be freed from sysfs interface created by the patch. - * This work allows to wait until the interface is destroyed in a separate - * context. - */ -static void klp_free_patch_work_fn(struct work_struct *work) -{ - struct klp_patch *patch = - container_of(work, struct klp_patch, free_work); - - klp_free_patch_finish(patch); -} - -static void klp_free_patch_async(struct klp_patch *patch) +static void klp_free_patch(struct klp_patch *patch) { klp_free_patch_start(patch); - schedule_work(&patch->free_work); + klp_free_patch_finish(patch); } -void klp_free_patches_async(struct list_head *to_free) +void klp_free_patches(struct list_head *to_free) { struct klp_patch *patch, *tmp_patch; list_for_each_entry_safe(patch, tmp_patch, to_free, list) { list_del_init(&patch->list); - klp_free_patch_async(patch); + klp_free_patch(patch); } } @@ -873,7 +868,6 @@ static int klp_init_patch_early(struct klp_patch *patch) kobject_init(&patch->kobj, &klp_ktype_patch); patch->enabled = false; patch->forced = false; - INIT_WORK(&patch->free_work, klp_free_patch_work_fn); klp_for_each_object_static(patch, obj) { if (!obj->funcs) diff --git a/kernel/livepatch/core.h b/kernel/livepatch/core.h index 8ff97745ba40..ea593f370049 100644 --- a/kernel/livepatch/core.h +++ b/kernel/livepatch/core.h @@ -13,7 +13,7 @@ extern struct list_head klp_patches; #define klp_for_each_patch(patch) \ list_for_each_entry(patch, &klp_patches, list) -void klp_free_patches_async(struct list_head *to_free); +void klp_free_patches(struct list_head *to_free); void klp_unpatch_replaced_patches(struct klp_patch *new_patch); void klp_discard_nops(struct klp_patch *new_patch); diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c index a9ebc9c5db02..3eff5fc0deee 100644 --- a/kernel/livepatch/transition.c +++ b/kernel/livepatch/transition.c @@ -41,7 +41,7 @@ static void klp_transition_work_fn(struct work_struct *work) mutex_unlock(&klp_mutex); - klp_free_patches_async(&to_free); + klp_free_patches(&to_free); } static DECLARE_DELAYED_WORK(klp_transition_work, klp_transition_work_fn); -- 2.31.1 Thanks, Ming