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 X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84D5DC34031 for ; Wed, 19 Feb 2020 02:45:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 528BB24655 for ; Wed, 19 Feb 2020 02:45:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582080318; bh=5uEBsRxClyuvVqGJzio9egBbCPvJMHgtyV3IoADzuMs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=gLUksaxKgKiq13FE33fIGAwsxzmmxeINW/th9Pro/MwzFZwfymK8VMpc5G2p7JyDC J2Hictc3O3icTjsguUJ6Nz6GTv6zx1qD2+hi+gz0vloMV3XLvXmk3WS2IEu2HiqnJz U5+xlorcKBZuQ1MwPsN5Jav7K6MPhJhGG6AlB6vI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728203AbgBSCpR (ORCPT ); Tue, 18 Feb 2020 21:45:17 -0500 Received: from mail.kernel.org ([198.145.29.99]:32942 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727187AbgBSCpR (ORCPT ); Tue, 18 Feb 2020 21:45:17 -0500 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (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 221B624654; Wed, 19 Feb 2020 02:45:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582080316; bh=5uEBsRxClyuvVqGJzio9egBbCPvJMHgtyV3IoADzuMs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=NWCPon5+OMi/0Ypox5wjReXfI94UJLME8bzLQrf1B8AAVbTpkXX/mbUwacXbYo58f MEgBLK/qqo4PPxjRi3sWOkO+njPGKfTNBF457tpkLDzd3NwEojC1zic3JLIkY8F/J0 GMbFa+acEz94szuHDiqbstsd22rR/UZV2VD4SyrE= Date: Wed, 19 Feb 2020 11:45:10 +0900 From: Masami Hiramatsu To: paulmck@kernel.org Cc: Steven Rostedt , Masami Hiramatsu , Joel Fernandes , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, mingo@kernel.org, gregkh@linuxfoundation.org, gustavo@embeddedor.com, tglx@linutronix.de, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com Subject: Re: [PATCH v2 3/9] rcu,tracing: Create trace_rcu_{enter,exit}() Message-Id: <20200219114510.6f942b56868a97e06352738c@kernel.org> In-Reply-To: <20200218201806.GI2935@paulmck-ThinkPad-P72> References: <20200213163800.5c51a5f1@gandalf.local.home> <20200213215004.GM2935@paulmck-ThinkPad-P72> <20200213170451.690c4e5c@gandalf.local.home> <20200213223918.GN2935@paulmck-ThinkPad-P72> <20200214151906.b1354a7ed6b01fc3bf2de862@kernel.org> <20200215145934.GD2935@paulmck-ThinkPad-P72> <20200217175519.12a694a969c1a8fb2e49905e@kernel.org> <20200217163112.GM2935@paulmck-ThinkPad-P72> <20200218133335.c87d7b2399ee6532bf28b74a@kernel.org> <20200218124609.1a33f868@gandalf.local.home> <20200218201806.GI2935@paulmck-ThinkPad-P72> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 18 Feb 2020 12:18:06 -0800 "Paul E. McKenney" wrote: > On Tue, Feb 18, 2020 at 12:46:09PM -0500, Steven Rostedt wrote: > > On Tue, 18 Feb 2020 13:33:35 +0900 > > Masami Hiramatsu wrote: > > > > > On Mon, 17 Feb 2020 08:31:12 -0800 > > > "Paul E. McKenney" wrote: > > > > > > > > > BTW, if you consider the x86 specific code is in the generic file, > > > > > we can move NOKPROBE_SYMBOL() in arch/x86/kernel/traps.c. > > > > > (Sorry, I've hit this idea right now) > > > > > > > > Might this affect other architectures with NMIs and probe-like things? > > > > If so, it might make sense to leave it where it is. > > > > > > Yes, git grep shows that arm64 is using rcu_nmi_enter() in > > > debug_exception_enter(). > > > OK, let's keep it, but maybe it is good to update the comment for > > > arm64 too. What about following? > > > > > > +/* > > > + * All functions in do_int3() on x86, do_debug_exception() on arm64 must be > > > + * marked NOKPROBE before kprobes handler is called. > > > + * ist_enter() on x86 and debug_exception_enter() on arm64 which is called > > > + * before kprobes handle happens to call rcu_nmi_enter() which means > > > + * that rcu_nmi_enter() must be marked NOKRPOBE. > > > + */ > > > > > > > Ah, why don't we just say... > > > > /* > > * All functions called in the breakpoint trap handler (e.g. do_int3() > > * on x86), must not allow kprobes until the kprobe breakpoint handler > > * is called, otherwise it can cause an infinite recursion. > > * On some archs, rcu_nmi_enter() is called in the breakpoint handler > > * before the kprobe breakpoint handler is called, thus it must be > > * marked as NOKPROBE. > > */ > > > > And that way we don't make this an arch specific comment. > > That looks good to me. Masami, does this work for you? Yes, that looks good to me too :) Thank you! -- Masami Hiramatsu