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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 08A16C4332F for ; Wed, 13 Oct 2021 01:47:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E17BF60E09 for ; Wed, 13 Oct 2021 01:47:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236720AbhJMBti (ORCPT ); Tue, 12 Oct 2021 21:49:38 -0400 Received: from out30-56.freemail.mail.aliyun.com ([115.124.30.56]:56803 "EHLO out30-56.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236699AbhJMBtg (ORCPT ); Tue, 12 Oct 2021 21:49:36 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R181e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04400;MF=yun.wang@linux.alibaba.com;NM=1;PH=DS;RN=31;SR=0;TI=SMTPD_---0UrdGZW4_1634089648; Received: from testdeMacBook-Pro.local(mailfrom:yun.wang@linux.alibaba.com fp:SMTPD_---0UrdGZW4_1634089648) by smtp.aliyun-inc.com(127.0.0.1); Wed, 13 Oct 2021 09:47:29 +0800 Subject: Re: [PATCH 1/2] ftrace: disable preemption on the testing of recursion To: Steven Rostedt Cc: Guo Ren , Ingo Molnar , "James E.J. Bottomley" , Helge Deller , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Paul Walmsley , Palmer Dabbelt , Albert Ou , Thomas Gleixner , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Josh Poimboeuf , Jiri Kosina , Miroslav Benes , Petr Mladek , Joe Lawrence , Colin Ian King , Masami Hiramatsu , "Peter Zijlstra (Intel)" , Nicholas Piggin , Jisheng Zhang , linux-csky@vger.kernel.org, linux-kernel@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, live-patching@vger.kernel.org References: <8c7de46d-9869-aa5e-2bb9-5dbc2eda395e@linux.alibaba.com> <20211012081728.5d357d6c@gandalf.local.home> From: =?UTF-8?B?546L6LSH?= Message-ID: Date: Wed, 13 Oct 2021 09:46:42 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20211012081728.5d357d6c@gandalf.local.home> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/10/12 δΈ‹εˆ8:17, Steven Rostedt wrote: > On Tue, 12 Oct 2021 13:40:08 +0800 > ηŽ‹θ΄‡ wrote: > >> @@ -52,11 +52,6 @@ static void notrace klp_ftrace_handler(unsigned long ip, >> bit = ftrace_test_recursion_trylock(ip, parent_ip); >> if (WARN_ON_ONCE(bit < 0)) >> return; >> - /* >> - * A variant of synchronize_rcu() is used to allow patching functions >> - * where RCU is not watching, see klp_synchronize_transition(). >> - */ > > I have to take a deeper look at this patch set, but do not remove this > comment, as it explains the protection here, that is not obvious with the > changes you made. Will keep that in v2. Regards, Michael Wang > > -- Steve > > >> - preempt_disable_notrace(); >> >> func = list_first_or_null_rcu(&ops->func_stack, struct klp_func, >> stack_node);