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 03AB0C433EF for ; Wed, 27 Oct 2021 01:55:58 +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 E813661073 for ; Wed, 27 Oct 2021 01:55:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org E813661073 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 4HfBcC06x4z3bsp for ; Wed, 27 Oct 2021 12:55:55 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux.alibaba.com (client-ip=115.124.30.132; helo=out30-132.freemail.mail.aliyun.com; envelope-from=yun.wang@linux.alibaba.com; receiver=) Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) (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 4HfBbj5bcfz2xBm for ; Wed, 27 Oct 2021 12:55:23 +1100 (AEDT) X-Alimail-AntiSpam: AC=PASS; BC=-1|-1; BR=01201311R441e4; CH=green; DM=||false|; DS=||; FP=0|-1|-1|-1|0|-1|-1|-1; HT=e01e04423; MF=yun.wang@linux.alibaba.com; NM=1; PH=DS; RN=30; SR=0; TI=SMTPD_---0UtpFhNO_1635299711; Received: from testdeMacBook-Pro.local(mailfrom:yun.wang@linux.alibaba.com fp:SMTPD_---0UtpFhNO_1635299711) by smtp.aliyun-inc.com(127.0.0.1); Wed, 27 Oct 2021 09:55:13 +0800 Subject: Re: [PATCH v5 1/2] ftrace: disable preemption when recursion locked To: Steven Rostedt References: <3ca92dc9-ea04-ddc2-71cd-524bfa5a5721@linux.alibaba.com> <333cecfe-3045-8e0a-0c08-64ff590845ab@linux.alibaba.com> <18ba2a71-e12d-33f7-63fe-2857b2db022c@linux.alibaba.com> <20211026080117.366137a5@gandalf.local.home> From: =?UTF-8?B?546L6LSH?= Message-ID: <3d897161-7b74-944a-f2a0-07311436fbd9@linux.alibaba.com> Date: Wed, 27 Oct 2021 09:54:13 +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: <20211026080117.366137a5@gandalf.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 , 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 , Paul Mackerras , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 2021/10/26 δΈ‹εˆ8:01, Steven Rostedt wrote: > On Tue, 26 Oct 2021 17:48:10 +0800 > ηŽ‹θ΄‡ wrote: > >>> The two comments should be updated too since Steven removed the "bit == 0" >>> trick. >> >> Could you please give more hint on how will it be correct? >> >> I get the point that bit will no longer be 0, there are only -1 or > 0 now >> so trace_test_and_set_recursion() will disable preemption on bit > 0 and >> trace_clear_recursion() will enabled it since it should only be called when >> bit > 0 (I remember we could use a WARN_ON here now :-P). >> >>> >>>> @@ -178,7 +187,7 @@ static __always_inline void trace_clear_recursion(int bit) >>>> * tracing recursed in the same context (normal vs interrupt), >>>> * >>>> * Returns: -1 if a recursion happened. >>>> - * >= 0 if no recursion >>>> + * > 0 if no recursion. >>>> */ >>>> static __always_inline int ftrace_test_recursion_trylock(unsigned long ip, >>>> unsigned long parent_ip) >>> >>> And this change would not be correct now. >> >> I thought it will no longer return 0 so I change it to > 0, isn't that correct? > > No it is not. I removed the bit + 1 return value, which means it returns the > actual bit now. Which is 0 or more. Ah, the return is bit not val, I must be drunk... My apologize for the stupid comments... I'll send a v6 for this patch only to fix that, please let me know if this is not a good way to fix few lines of comments. Regards, Michael Wang > > -- Steve >