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 9D6EEC433FE for ; Wed, 13 Oct 2021 02:28:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7CCAB60F92 for ; Wed, 13 Oct 2021 02:28:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235120AbhJMCaI convert rfc822-to-8bit (ORCPT ); Tue, 12 Oct 2021 22:30:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:43074 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233316AbhJMCaH (ORCPT ); Tue, 12 Oct 2021 22:30:07 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 17A2560F11; Wed, 13 Oct 2021 02:28:00 +0000 (UTC) Date: Tue, 12 Oct 2021 22:27:58 -0400 From: Steven Rostedt To: =?UTF-8?B?546L6LSH?= Cc: Miroslav Benes , 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 , 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 Subject: Re: [PATCH 1/2] ftrace: disable preemption on the testing of recursion Message-ID: <20211012222758.1a029157@oasis.local.home> In-Reply-To: <74090798-7d93-0713-982c-6f0247118d20@linux.alibaba.com> References: <8c7de46d-9869-aa5e-2bb9-5dbc2eda395e@linux.alibaba.com> <74090798-7d93-0713-982c-6f0247118d20@linux.alibaba.com> X-Mailer: Claws Mail 3.18.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On Wed, 13 Oct 2021 09:50:17 +0800 王贇 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. -- Steve > > Seems like this lock pair was supposed to take care the preemtion itself? 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 C446DC433F5 for ; Wed, 13 Oct 2021 02:28:30 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 8D01160F92 for ; Wed, 13 Oct 2021 02:28:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 8D01160F92 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=uY/VTxE+Glm4PK048PV9vV8VmSvC74XA0oUw0yTaVy4=; b=o6e6LS+PzQKMnR UlYUpYUbaEMu90DV9g1KLiDUSHKsYMoaCAOgZtPHlWpLQBe7VKmmdH7ujVNqLrrpDeoBJTXGh72md Vd7uUHnfe8zvVCPTZIDNRAJ18AbCz/cfvJBwCtTj6k122BI/JuhVLRWkuh4AX7c0q4A3vG2KfZjX9 0aFn8LevAGXQtI0/UMboRtKpuiMkrioepWM4XTf6gwp+roLrkg3AG2/yLATwDT1MLWm+2sfOh4tQe E2wVlHlm+YWZcSLN6fNCeM6VOfkSecqVBoldPbiakgVGPH1ZJitbWd7ghzSZP28sYDLUKDnxt+jco y3i1b+oat302bo06bV8A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1maTzy-00EeCl-Rs; Wed, 13 Oct 2021 02:28:06 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1maTzv-00EeBA-FN for linux-riscv@lists.infradead.org; Wed, 13 Oct 2021 02:28:04 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 17A2560F11; Wed, 13 Oct 2021 02:28:00 +0000 (UTC) Date: Tue, 12 Oct 2021 22:27:58 -0400 From: Steven Rostedt To: =?UTF-8?B?546L6LSH?= Cc: Miroslav Benes , 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 , 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 Subject: Re: [PATCH 1/2] ftrace: disable preemption on the testing of recursion Message-ID: <20211012222758.1a029157@oasis.local.home> In-Reply-To: <74090798-7d93-0713-982c-6f0247118d20@linux.alibaba.com> References: <8c7de46d-9869-aa5e-2bb9-5dbc2eda395e@linux.alibaba.com> <74090798-7d93-0713-982c-6f0247118d20@linux.alibaba.com> X-Mailer: Claws Mail 3.18.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211012_192803_554185_08E69D75 X-CRM114-Status: GOOD ( 17.17 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; 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Wed, 13 Oct 2021 13:28:06 +1100 (AEDT) Received: by mail.kernel.org (Postfix) with ESMTPSA id 17A2560F11; Wed, 13 Oct 2021 02:28:00 +0000 (UTC) Date: Tue, 12 Oct 2021 22:27:58 -0400 From: Steven Rostedt To: =?UTF-8?B?546L6LSH?= Subject: Re: [PATCH 1/2] ftrace: disable preemption on the testing of recursion Message-ID: <20211012222758.1a029157@oasis.local.home> In-Reply-To: <74090798-7d93-0713-982c-6f0247118d20@linux.alibaba.com> References: <8c7de46d-9869-aa5e-2bb9-5dbc2eda395e@linux.alibaba.com> <74090798-7d93-0713-982c-6f0247118d20@linux.alibaba.com> X-Mailer: Claws Mail 3.18.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 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 Wed, 13 Oct 2021 09:50:17 +0800 =E7=8E=8B=E8=B4=87 wrote: > >> - preempt_enable_notrace(); > >> ftrace_test_recursion_unlock(bit); > >> } =20 > >=20 > > I don't like this change much. We have preempt_disable there not becaus= e=20 > > of ftrace_test_recursion, but because of RCU. ftrace_test_recursion was= =20 > > added later. Yes, it would work with the change, but it would also hide= =20 > > things which should not be hidden in my opinion. =20 >=20 > Not very sure about the backgroup stories, but just found this in > 'Documentation/trace/ftrace-uses.rst': >=20 > Note, on success, > ftrace_test_recursion_trylock() will disable preemption, and the > ftrace_test_recursion_unlock() will enable it again (if it was previous= ly > 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. -- Steve >=20 > Seems like this lock pair was supposed to take care the preemtion itself?