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=-5.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 F0A1AC34047 for ; Wed, 19 Feb 2020 16:45:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C4A3A24656 for ; Wed, 19 Feb 2020 16:45:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582130747; bh=IzfEf9eLgE8F8pz7bfZaRUiusn9TiUNKDkI24ysHkws=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=buKYF7yUFzp/V3n9tOry6AwBdgD4VQMTRqflkf90X6SmGCXZYqfAxoSKzN1D2usyf 9r+RWUMb2UvweOhiNqYUKGnJ6KVrtBk360VfrDGUEHOKnp58OKAh6zWYY+wYz5zw9w 7S0CJwS+QBLHZeqq1yODrQrpC3IbxpRm7HW1T+OI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726820AbgBSQpq (ORCPT ); Wed, 19 Feb 2020 11:45:46 -0500 Received: from mail.kernel.org ([198.145.29.99]:34138 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726551AbgBSQpq (ORCPT ); Wed, 19 Feb 2020 11:45:46 -0500 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (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 19ABC20578; Wed, 19 Feb 2020 16:45:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582130745; bh=IzfEf9eLgE8F8pz7bfZaRUiusn9TiUNKDkI24ysHkws=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=WWTQfPoT/JtbsiGP5ir+kOvBjroYp/fwaJOLdZbaMN+eRfLzyccwpKnifAX/SqHhd S6p1ewPDPPRGcSEoOj9bc6ffImeJhEFOc5YHzk1FDa5aAjhPoKF7ZMNPqKt6ir2N+/ Gj9JvXKfxxlNxWfPdo4PbWZnBGTt0QpnRhPcXUFg= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id ECCC335209B0; Wed, 19 Feb 2020 08:45:44 -0800 (PST) Date: Wed, 19 Feb 2020 08:45:44 -0800 From: "Paul E. McKenney" To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, rostedt@goodmis.org, mingo@kernel.org, joel@joelfernandes.org, gregkh@linuxfoundation.org, gustavo@embeddedor.com, tglx@linutronix.de, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, luto@kernel.org, tony.luck@intel.com, frederic@kernel.org, dan.carpenter@oracle.com, mhiramat@kernel.org Subject: Re: [PATCH v3 05/22] rcu: Make RCU IRQ enter/exit functions rely on in_nmi() Message-ID: <20200219164544.GD2935@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200219144724.800607165@infradead.org> <20200219150744.661923520@infradead.org> <20200219163156.GY2935@paulmck-ThinkPad-P72> <20200219163700.GK18400@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200219163700.GK18400@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 19, 2020 at 05:37:00PM +0100, Peter Zijlstra wrote: > On Wed, Feb 19, 2020 at 08:31:56AM -0800, Paul E. McKenney wrote: > > On Wed, Feb 19, 2020 at 03:47:29PM +0100, Peter Zijlstra wrote: > > > From: Paul E. McKenney > > > > > > The rcu_nmi_enter_common() and rcu_nmi_exit_common() functions take an > > > "irq" parameter that indicates whether these functions are invoked from > > > an irq handler (irq==true) or an NMI handler (irq==false). However, > > > recent changes have applied notrace to a few critical functions such > > > that rcu_nmi_enter_common() and rcu_nmi_exit_common() many now rely > > > on in_nmi(). Note that in_nmi() works no differently than before, > > > but rather that tracing is now prohibited in code regions where in_nmi() > > > would incorrectly report NMI state. > > > > > > This commit therefore removes the "irq" parameter and inlines > > > rcu_nmi_enter_common() and rcu_nmi_exit_common() into rcu_nmi_enter() > > > and rcu_nmi_exit(), respectively. > > > > > > Signed-off-by: Paul E. McKenney > > > Signed-off-by: Peter Zijlstra (Intel) > > > > Again, thank you. > > > > Would you like to also take the added comment for NOKPROBE_SYMBOL(), > > or would you prefer that I carry that separately? (I dropped it for > > now to avoid the conflict with the patch below.) > > > > Here is the latest version of that comment, posted by Steve Rostedt. > > > > Thanx, Paul > > > > /* > > * 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. > > */ > > Oh right, let me stick that in a separate patch. Best we not loose that > I suppose ;-) There was a lot of effort spent on it, to be sure. ;-) ;-) ;-) Thanx, Paul