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 A3AE3C433FE for ; Wed, 13 Oct 2021 02:31:12 +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 C49E860FDA for ; Wed, 13 Oct 2021 02:31:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org C49E860FDA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org 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 4HTc3L3DY0z3bj0 for ; Wed, 13 Oct 2021 13:31:10 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=198.145.29.99; helo=mail.kernel.org; envelope-from=srs0=7yos=pb=goodmis.org=rostedt@kernel.org; receiver=) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4HTc2t4Ktxz2xXh for ; Wed, 13 Oct 2021 13:30:46 +1100 (AEDT) Received: by mail.kernel.org (Postfix) with ESMTPSA id DE40C6101D; Wed, 13 Oct 2021 02:30:40 +0000 (UTC) Date: Tue, 12 Oct 2021 22:30:39 -0400 From: Steven Rostedt To: =?UTF-8?B?546L6LSH?= Subject: Re: [PATCH 1/2] ftrace: disable preemption on the testing of recursion Message-ID: <20211012223039.78099c24@oasis.local.home> In-Reply-To: <1eab20c1-d69b-f94b-92ff-4329d0aff6a2@linux.alibaba.com> References: <8c7de46d-9869-aa5e-2bb9-5dbc2eda395e@linux.alibaba.com> <20211012084331.06b8dd23@gandalf.local.home> <1eab20c1-d69b-f94b-92ff-4329d0aff6a2@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 10:04:52 +0800 =E7=8E=8B=E8=B4=87 wrote: > I see, while the user can still check smp_processor_id() after trylock > return bit 0... But preemption would have already been disabled. That's because a bit 0 means that a recursion check has already been made by a previous caller and this one is nested, thus preemption is already disabled. If bit is 0, then preemption had better be disabled as well. -- Steve