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 E59B1C34050 for ; Wed, 19 Feb 2020 16:32:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B192D2067D for ; Wed, 19 Feb 2020 16:32:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582129921; bh=Z68qVfNQ0z0dRq0qrxhhTv3+OjeqcObk6RNhURSJoqQ=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=D0BALH0AZFHUeipH3XFgZ8v5XSlUVswaDqQEwhM+I7QNKtHBtIOYvmK7Yd5A5+Jp9 5HGL1TNVC9jPBj4KEToOhcA3VnNFS8DrOauIeQLtZOXUTtBP5eQ3hlsRFwOnoUJ6fe BY5CZtXXDXD3GP9RkMKKKcFcMHYzrhAsUkw7luSc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726871AbgBSQcA (ORCPT ); Wed, 19 Feb 2020 11:32:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:58444 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726729AbgBSQb6 (ORCPT ); Wed, 19 Feb 2020 11:31:58 -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 D0C7924654; Wed, 19 Feb 2020 16:31:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582129916; bh=Z68qVfNQ0z0dRq0qrxhhTv3+OjeqcObk6RNhURSJoqQ=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=TR4CmeF/wYivso8JLtehnGUsUcUBbraJDjSHAypO0Up2u/3F72KGjA7AyDSGo4li7 HTFHLn83v470Dga6IoApucm0FgG8CKKrFmyWXqQRn5OV1rkob8rGoWwQLwReRVkW6r uGE3bpz72GsgvWfkUpR8h/3jyyTP58JiHnLjvLxo= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id A87BB35209B0; Wed, 19 Feb 2020 08:31:56 -0800 (PST) Date: Wed, 19 Feb 2020 08:31:56 -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: <20200219163156.GY2935@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200219144724.800607165@infradead.org> <20200219150744.661923520@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200219150744.661923520@infradead.org> 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 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. */ > --- > kernel/rcu/tree.c | 45 ++++++++++++++------------------------------- > 1 file changed, 14 insertions(+), 31 deletions(-) > > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -614,16 +614,18 @@ void rcu_user_enter(void) > } > #endif /* CONFIG_NO_HZ_FULL */ > > -/* > +/** > + * rcu_nmi_exit - inform RCU of exit from NMI context > + * > * If we are returning from the outermost NMI handler that interrupted an > * RCU-idle period, update rdp->dynticks and rdp->dynticks_nmi_nesting > * to let the RCU grace-period handling know that the CPU is back to > * being RCU-idle. > * > - * If you add or remove a call to rcu_nmi_exit_common(), be sure to test > + * If you add or remove a call to rcu_nmi_exit(), be sure to test > * with CONFIG_RCU_EQS_DEBUG=y. > */ > -static __always_inline void rcu_nmi_exit_common(bool irq) > +void rcu_nmi_exit(void) > { > struct rcu_data *rdp = this_cpu_ptr(&rcu_data); > > @@ -651,27 +653,16 @@ static __always_inline void rcu_nmi_exit > trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, atomic_read(&rdp->dynticks)); > WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */ > > - if (irq) > + if (!in_nmi()) > rcu_prepare_for_idle(); > > rcu_dynticks_eqs_enter(); > > - if (irq) > + if (!in_nmi()) > rcu_dynticks_task_enter(); > } > > /** > - * rcu_nmi_exit - inform RCU of exit from NMI context > - * > - * If you add or remove a call to rcu_nmi_exit(), be sure to test > - * with CONFIG_RCU_EQS_DEBUG=y. > - */ > -void rcu_nmi_exit(void) > -{ > - rcu_nmi_exit_common(false); > -} > - > -/** > * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle > * > * Exit from an interrupt handler, which might possibly result in entering > @@ -693,7 +684,7 @@ void rcu_nmi_exit(void) > void rcu_irq_exit(void) > { > lockdep_assert_irqs_disabled(); > - rcu_nmi_exit_common(true); > + rcu_nmi_exit(); > } > > /* > @@ -777,7 +768,7 @@ void rcu_user_exit(void) > #endif /* CONFIG_NO_HZ_FULL */ > > /** > - * rcu_nmi_enter_common - inform RCU of entry to NMI context > + * rcu_nmi_enter - inform RCU of entry to NMI context > * @irq: Is this call from rcu_irq_enter? > * > * If the CPU was idle from RCU's viewpoint, update rdp->dynticks and > @@ -786,10 +777,10 @@ void rcu_user_exit(void) > * long as the nesting level does not overflow an int. (You will probably > * run out of stack space first.) > * > - * If you add or remove a call to rcu_nmi_enter_common(), be sure to test > + * If you add or remove a call to rcu_nmi_enter(), be sure to test > * with CONFIG_RCU_EQS_DEBUG=y. > */ > -static __always_inline void rcu_nmi_enter_common(bool irq) > +void rcu_nmi_enter(void) > { > long incby = 2; > struct rcu_data *rdp = this_cpu_ptr(&rcu_data); > @@ -807,12 +798,12 @@ static __always_inline void rcu_nmi_ente > */ > if (rcu_dynticks_curr_cpu_in_eqs()) { > > - if (irq) > + if (!in_nmi()) > rcu_dynticks_task_exit(); > > rcu_dynticks_eqs_exit(); > > - if (irq) > + if (!in_nmi()) > rcu_cleanup_after_idle(); > > incby = 1; > @@ -834,14 +825,6 @@ static __always_inline void rcu_nmi_ente > rdp->dynticks_nmi_nesting + incby); > barrier(); > } > - > -/** > - * rcu_nmi_enter - inform RCU of entry to NMI context > - */ > -void rcu_nmi_enter(void) > -{ > - rcu_nmi_enter_common(false); > -} > NOKPROBE_SYMBOL(rcu_nmi_enter); > > /** > @@ -869,7 +852,7 @@ NOKPROBE_SYMBOL(rcu_nmi_enter); > void rcu_irq_enter(void) > { > lockdep_assert_irqs_disabled(); > - rcu_nmi_enter_common(true); > + rcu_nmi_enter(); > } > > /* > >