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 E2452C433F5 for ; Wed, 13 Oct 2021 02:36:59 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6EB9360F23 for ; Wed, 13 Oct 2021 02:36:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 6EB9360F23 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.ozlabs.org Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4HTcB14gJBz3bWT for ; Wed, 13 Oct 2021 13:36:57 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux.alibaba.com (client-ip=115.124.30.131; helo=out30-131.freemail.mail.aliyun.com; envelope-from=yun.wang@linux.alibaba.com; receiver=) Received: from out30-131.freemail.mail.aliyun.com (out30-131.freemail.mail.aliyun.com [115.124.30.131]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4HTc9W6mMQz2xh0 for ; Wed, 13 Oct 2021 13:36:25 +1100 (AEDT) X-Alimail-AntiSpam: AC=PASS; BC=-1|-1; BR=01201311R201e4; CH=green; DM=||false|; DS=||; FP=0|-1|-1|-1|0|-1|-1|-1; HT=e01e04357; MF=yun.wang@linux.alibaba.com; NM=1; PH=DS; RN=31; SR=0; TI=SMTPD_---0Urdkedq_1634092576; Received: from testdeMacBook-Pro.local(mailfrom:yun.wang@linux.alibaba.com fp:SMTPD_---0Urdkedq_1634092576) by smtp.aliyun-inc.com(127.0.0.1); Wed, 13 Oct 2021 10:36:18 +0800 Subject: Re: [PATCH 1/2] ftrace: disable preemption on the testing of recursion To: Steven Rostedt References: <8c7de46d-9869-aa5e-2bb9-5dbc2eda395e@linux.alibaba.com> <74090798-7d93-0713-982c-6f0247118d20@linux.alibaba.com> <20211012222758.1a029157@oasis.local.home> From: =?UTF-8?B?546L6LSH?= Message-ID: <4b4be164-0095-90bc-a193-faa7100558d2@linux.alibaba.com> Date: Wed, 13 Oct 2021 10:36:16 +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: <20211012222758.1a029157@oasis.local.home> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Peter Zijlstra \(Intel\)" , Paul Walmsley , "James E.J. Bottomley" , Guo Ren , Jisheng Zhang , "H. Peter Anvin" , live-patching@vger.kernel.org, linux-riscv@lists.infradead.org, Miroslav Benes , Paul Mackerras , Joe Lawrence , Helge Deller , x86@kernel.org, linux-csky@vger.kernel.org, Ingo Molnar , Petr Mladek , Albert Ou , Jiri Kosina , Nicholas Piggin , Borislav Petkov , Josh Poimboeuf , Thomas Gleixner , linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org, Palmer Dabbelt , Masami Hiramatsu , Colin Ian King , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 2021/10/13 上午10:27, Steven Rostedt wrote: > On Wed, 13 Oct 2021 09:50:17 +0800 > ηŽ‹θ΄‡ wrote: > >>>> - preempt_enable_notrace(); >>>> ftrace_test_recursion_unlock(bit); >>>> } >>> >>> I don't like this change much. We have preempt_disable there not because >>> of ftrace_test_recursion, but because of RCU. ftrace_test_recursion was >>> added later. Yes, it would work with the change, but it would also hide >>> things which should not be hidden in my opinion. >> >> Not very sure about the backgroup stories, but just found this in >> 'Documentation/trace/ftrace-uses.rst': >> >> Note, on success, >> ftrace_test_recursion_trylock() will disable preemption, and the >> ftrace_test_recursion_unlock() will enable it again (if it was previously >> enabled). > > Right that part is to be fixed by what you are adding here. > > The point that Miroslav is complaining about is that the preemption > disabling is special in this case, and not just from the recursion > point of view, which is why the comment is still required. My bad... the title do confusing people, will rewrite it. Regards, Michael Wang > > -- Steve > > >> >> Seems like this lock pair was supposed to take care the preemtion itself?