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 90413C433F5 for ; Tue, 26 Oct 2021 12:01:51 +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 BF88A60F0F for ; Tue, 26 Oct 2021 12:01:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org BF88A60F0F 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 4Hdr5n0FVRz30RN for ; Tue, 26 Oct 2021 23:01:49 +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=c3ca=po=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 4Hdr5J5mDxz2xvf for ; Tue, 26 Oct 2021 23:01:24 +1100 (AEDT) Received: from gandalf.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 425F3601FC; Tue, 26 Oct 2021 12:01:19 +0000 (UTC) Date: Tue, 26 Oct 2021 08:01:17 -0400 From: Steven Rostedt To: =?UTF-8?B?546L6LSH?= Subject: Re: [PATCH v5 1/2] ftrace: disable preemption when recursion locked Message-ID: <20211026080117.366137a5@gandalf.local.home> In-Reply-To: <18ba2a71-e12d-33f7-63fe-2857b2db022c@linux.alibaba.com> 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> 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 Tue, 26 Oct 2021 17:48:10 +0800 =E7=8E=8B=E8=B4=87 wrote: > > The two comments should be updated too since Steven removed the "bit = =3D=3D 0"=20 > > trick. =20 >=20 > Could you please give more hint on how will it be correct? >=20 > 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 wh= en > bit > 0 (I remember we could use a WARN_ON here now :-P). >=20 > > =20 > >> @@ -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. > >> - * >=3D 0 if no recursion > >> + * > 0 if no recursion. > >> */ > >> static __always_inline int ftrace_test_recursion_trylock(unsigned lon= g ip, > >> unsigned long parent_ip) =20 > >=20 > > And this change would not be correct now. =20 >=20 > I thought it will no longer return 0 so I change it to > 0, isn't that co= rrect? No it is not. I removed the bit + 1 return value, which means it returns the actual bit now. Which is 0 or more. -- Steve