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 0B3A8ECAAD3 for ; Thu, 1 Sep 2022 13:45:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232512AbiIANpl (ORCPT ); Thu, 1 Sep 2022 09:45:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59622 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231668AbiIANpk (ORCPT ); Thu, 1 Sep 2022 09:45:40 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 65C16D78; Thu, 1 Sep 2022 06:45:33 -0700 (PDT) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4MJMgW4MFdznTs2; Thu, 1 Sep 2022 21:43:03 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500024.china.huawei.com (7.185.36.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 1 Sep 2022 21:45:31 +0800 Received: from [10.174.178.55] (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 1 Sep 2022 21:45:30 +0800 Subject: Re: [PATCH] livepatch: Move error print out of lock protection in klp_enable_patch() To: Joe Lawrence CC: Josh Poimboeuf , Jiri Kosina , Miroslav Benes , Petr Mladek , , References: <20220901022706.813-1-thunder.leizhen@huawei.com> <65fe1978-60da-5bd4-9559-fddec13f03bf@redhat.com> From: "Leizhen (ThunderTown)" Message-ID: <19e0d24c-366a-a269-8c4d-bf32831e2079@huawei.com> Date: Thu, 1 Sep 2022 21:45:30 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <65fe1978-60da-5bd4-9559-fddec13f03bf@redhat.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On 2022/9/1 21:24, Joe Lawrence wrote: > On 8/31/22 10:27 PM, Zhen Lei wrote: >> The patch->mod is not a protected object of mutex_lock(&klp_mutex). Since >> it's in the error handling branch, it might not be helpful to reduce lock >> conflicts, but it can reduce some code size. >> >> Before: >> text data bss dec hex filename >> 10330 464 8 10802 2a32 kernel/livepatch/core.o >> >> After: >> text data bss dec hex filename >> 10307 464 8 10779 2a1b kernel/livepatch/core.o >> > > Is a size change expected, or is it just compiler fall out from > shuffling the code around a little bit? I thought it was because mutex_lock()/mutex_unlock() was close enough to reduce a "&klp_mutex" operation. Now, I was wrong. > > I see some arches do a little better, some a little worse with gcc-9.3.0 > cross compilers: Sorry. This is what I should have done. I built it on x86_64 with gcc-8.4.0 > > Before > ------ > text data bss dec hex filename > 8490 600 8 9098 238a arm64/kernel/livepatch/core.o > 9424 680 8 10112 2780 s390/kernel/livepatch/core.o > 9802 228 4 10034 2732 ppc32/kernel/livepatch/core.o > 13746 456 8 14210 3782 ppc64le/kernel/livepatch/core.o > 10443 464 8 10915 2aa3 x86_64/kernel/livepatch/core.o > > > After > ----- > text data bss dec hex filename > 8514 600 8 9122 23a2 arm64/kernel/livepatch/core.o > 9424 680 8 10112 2780 s390/kernel/livepatch/core.o > 9818 228 4 10050 2742 ppc32/kernel/livepatch/core.o > 13762 456 8 14226 3792 ppc64le/kernel/livepatch/core.o > 10446 464 8 10918 2aa6 x86_64/kernel/livepatch/core.o > > In which case, I'd just omit the size savings from the commit msg. OK. Should I send v2 to update commit message? > >> Signed-off-by: Zhen Lei >> --- >> kernel/livepatch/core.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c >> index 42f7e716d56bf72..cb7abc821a50584 100644 >> --- a/kernel/livepatch/core.c >> +++ b/kernel/livepatch/core.c >> @@ -1041,9 +1041,9 @@ int klp_enable_patch(struct klp_patch *patch) >> mutex_lock(&klp_mutex); >> >> if (!klp_is_patch_compatible(patch)) { >> + mutex_unlock(&klp_mutex); >> pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n", >> patch->mod->name); >> - mutex_unlock(&klp_mutex); >> return -EINVAL; >> } >> >> > > That said, I don't see anything obviously wrong about the change (we > don't need to sync our error msgs, right?) so: Yes > > Acked-by: Joe Lawrence Thanks > -- Regards, Zhen Lei