From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: Re: [PATCH v2 3/9] rcu,tracing: Create trace_rcu_{enter,exit}() Date: Tue, 18 Feb 2020 11:35:03 -0500 Message-ID: <20200218113503.1170c188@gandalf.local.home> References: <20200213211930.GG170680@google.com> <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> <20200218161231.GD2935@paulmck-ThinkPad-P72> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from mail.kernel.org ([198.145.29.99]:57932 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726360AbgBRQfG (ORCPT ); Tue, 18 Feb 2020 11:35:06 -0500 In-Reply-To: <20200218161231.GD2935@paulmck-ThinkPad-P72> Sender: linux-arch-owner@vger.kernel.org List-ID: To: "Paul E. McKenney" Cc: 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 On Tue, 18 Feb 2020 08:12:31 -0800 "Paul E. McKenney" wrote: > Would it work to describe the general problem, then give x86 details > as a specific example, as follows? > > /* > * On some architectures, certain exceptions prohibit use of kprobes until > * the exception code path reaches a certain point. For example, on x86 all > * functions called by do_int3() must be marked NOKPROBE. However, once > * kprobe_int3_handler() is called, kprobing is permitted. Specifically, > * ist_enter() is called in do_int3() before kprobe_int3_handle(). > * Furthermore, ist_enter() calls rcu_nmi_enter(), which means that > * rcu_nmi_enter() must be marked NOKRPOBE. > */ > > That way, I don't feel like I need to update the commment each time > a new architecture adds this capability. ;-) I don't think this is going to be an issue for other archs, as they don't have an IST. -- Steve