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 5B0CEC433F5 for ; Wed, 27 Oct 2021 02:56:25 +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 B35F06103B for ; Wed, 27 Oct 2021 02:56:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org B35F06103B 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 4HfCxz0gVGz3c5B for ; Wed, 27 Oct 2021 13:56:23 +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=up5n=pp=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 4HfCxV6d2Kz2xB0 for ; Wed, 27 Oct 2021 13:55:58 +1100 (AEDT) Received: from rorschach.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 03365610C7; Wed, 27 Oct 2021 02:55:53 +0000 (UTC) Date: Tue, 26 Oct 2021 22:55:52 -0400 From: Steven Rostedt To: =?UTF-8?B?546L6LSH?= Subject: Re: [PATCH v6 1/2] ftrace: disable preemption when recursion locked Message-ID: <20211026225552.72a7ee79@rorschach.local.home> In-Reply-To: <78c95844-16b7-8904-b48d-3b2ccd76a352@linux.alibaba.com> References: <78c95844-16b7-8904-b48d-3b2ccd76a352@linux.alibaba.com> X-Mailer: Claws Mail 3.17.8 (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 , 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 Wed, 27 Oct 2021 10:34:13 +0800 =E7=8E=8B=E8=B4=87 wrote: > +/* > + * Preemption will be enabled (if it was previously enabled). > + */ > static __always_inline void trace_clear_recursion(int bit) > { > + WARN_ON_ONCE(bit < 0); Can you send a v7 without the WARN_ON. This is an extremely hot path, and this will cause noticeable overhead. If something were to call this with bit < 0, then it would crash and burn rather quickly. -- Steve > + > + preempt_enable_notrace(); > barrier(); > trace_recursion_clear(bit); > }