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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 303A3C433F5 for ; Thu, 10 Mar 2022 19:47:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243227AbiCJTs5 (ORCPT ); Thu, 10 Mar 2022 14:48:57 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37984 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241948AbiCJTsx (ORCPT ); Thu, 10 Mar 2022 14:48:53 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 936ABC12C1 for ; Thu, 10 Mar 2022 11:47:51 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 42192B826EE for ; Thu, 10 Mar 2022 19:47:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BAE7BC340E9; Thu, 10 Mar 2022 19:47:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1646941668; bh=F6qPmD6J4EH7sJSyBvQelcQinxF4YNR80JwP1J6a0us=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=uzflSV+bIM9uSyc+tM0ZwOJ2eUJ5vUXwlBnid/kalmcwbKrT2Azb1J/v17XOXhIGe c6atv3PVOkiepOohkv7O6mlbA8KmLvwVmcE4mFt6tSzt1kbg5euOPAvAt6rSfdfLXk iVgNt4gQ8yco9xWAwAN5fXCu/ASuKZzEcGmRJvYG3EQBg7qoTxyZInaTWw8XA2ep7H jqgxZ2z1SQUm2alX9XerBXxdu/hB6svnip23OpG65Dc92oaMgtwTSk/OXX2EsPL9ek NKy72IPoPGPGXHvdxia2hJU068WW42ly1CVQD9uqs5NH3N8dFky6WxfsS85TsKFgoM 68jN2L1S2xe3Q== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 72E615C0387; Thu, 10 Mar 2022 11:47:48 -0800 (PST) Date: Thu, 10 Mar 2022 11:47:48 -0800 From: "Paul E. McKenney" To: Frederic Weisbecker Cc: LKML , Peter Zijlstra , Phil Auld , Alex Belits , Nicolas Saenz Julienne , Xiongfeng Wang , Neeraj Upadhyay , Thomas Gleixner , Yu Liao , Boqun Feng , Marcelo Tosatti , Paul Gortmaker , Uladzislau Rezki , Joel Fernandes Subject: Re: [PATCH 08/19] context_tracking: Take NMI eqs entrypoints over RCU Message-ID: <20220310194748.GV4285@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20220302154810.42308-1-frederic@kernel.org> <20220302154810.42308-9-frederic@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220302154810.42308-9-frederic@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 02, 2022 at 04:47:59PM +0100, Frederic Weisbecker wrote: > The RCU dynticks counter is going to be merged into the context tracking > subsystem. Prepare with moving the NMI extended quiescent states > entrypoints to context tracking. For now those are dumb redirection to > existing RCU calls. > > Signed-off-by: Frederic Weisbecker Acked-by: Paul E. McKenney > Cc: Paul E. McKenney > Cc: Peter Zijlstra > Cc: Thomas Gleixner > Cc: Neeraj Upadhyay > Cc: Uladzislau Rezki > Cc: Joel Fernandes > Cc: Boqun Feng > Cc: Nicolas Saenz Julienne > Cc: Marcelo Tosatti > Cc: Xiongfeng Wang > Cc: Yu Liao > Cc: Phil Auld > Cc: Paul Gortmaker > Cc: Alex Belits > --- > Documentation/RCU/Design/Requirements/Requirements.rst | 2 +- > arch/Kconfig | 2 +- > arch/arm64/kernel/entry-common.c | 8 ++++---- > include/linux/context_tracking_irq.h | 4 ++++ > include/linux/hardirq.h | 4 ++-- > kernel/context_tracking.c | 10 ++++++++++ > kernel/entry/common.c | 4 ++-- > kernel/extable.c | 4 ++-- > kernel/trace/trace.c | 2 +- > 9 files changed, 27 insertions(+), 13 deletions(-) > > diff --git a/Documentation/RCU/Design/Requirements/Requirements.rst b/Documentation/RCU/Design/Requirements/Requirements.rst > index e3dd5d71c798..256cf260e864 100644 > --- a/Documentation/RCU/Design/Requirements/Requirements.rst > +++ b/Documentation/RCU/Design/Requirements/Requirements.rst > @@ -1847,7 +1847,7 @@ normal interrupts. One way that this can happen is for code that > directly invokes ct_irq_enter() and ct_irq_exit() to be called > from an NMI handler. This astonishing fact of life prompted the current > code structure, which has ct_irq_enter() invoking > -rcu_nmi_enter() and ct_irq_exit() invoking rcu_nmi_exit(). > +ct_nmi_enter() and ct_irq_exit() invoking ct_nmi_exit(). > And yes, I also learned of this requirement the hard way. > > Loadable Modules > diff --git a/arch/Kconfig b/arch/Kconfig > index 66b2b6d4717b..c22b8ca0eb01 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -785,7 +785,7 @@ config HAVE_CONTEXT_TRACKING_USER_OFFSTACK > > - Critical entry code isn't preemptible (or better yet: > not interruptible). > - - No use of RCU read side critical sections, unless rcu_nmi_enter() > + - No use of RCU read side critical sections, unless ct_nmi_enter() > got called. > - No use of instrumentation, unless instrumentation_begin() got > called. > diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c > index 43ca8cf4e1dd..6a1ea28731c8 100644 > --- a/arch/arm64/kernel/entry-common.c > +++ b/arch/arm64/kernel/entry-common.c > @@ -158,7 +158,7 @@ static void noinstr arm64_enter_nmi(struct pt_regs *regs) > __nmi_enter(); > lockdep_hardirqs_off(CALLER_ADDR0); > lockdep_hardirq_enter(); > - rcu_nmi_enter(); > + ct_nmi_enter(); > > trace_hardirqs_off_finish(); > ftrace_nmi_enter(); > @@ -179,7 +179,7 @@ static void noinstr arm64_exit_nmi(struct pt_regs *regs) > lockdep_hardirqs_on_prepare(CALLER_ADDR0); > } > > - rcu_nmi_exit(); > + ct_nmi_exit(); > lockdep_hardirq_exit(); > if (restore) > lockdep_hardirqs_on(CALLER_ADDR0); > @@ -196,7 +196,7 @@ static void noinstr arm64_enter_el1_dbg(struct pt_regs *regs) > regs->lockdep_hardirqs = lockdep_hardirqs_enabled(); > > lockdep_hardirqs_off(CALLER_ADDR0); > - rcu_nmi_enter(); > + ct_nmi_enter(); > > trace_hardirqs_off_finish(); > } > @@ -215,7 +215,7 @@ static void noinstr arm64_exit_el1_dbg(struct pt_regs *regs) > lockdep_hardirqs_on_prepare(CALLER_ADDR0); > } > > - rcu_nmi_exit(); > + ct_nmi_exit(); > if (restore) > lockdep_hardirqs_on(CALLER_ADDR0); > } > diff --git a/include/linux/context_tracking_irq.h b/include/linux/context_tracking_irq.h > index 60e3ed15a04e..11043bf724b7 100644 > --- a/include/linux/context_tracking_irq.h > +++ b/include/linux/context_tracking_irq.h > @@ -7,11 +7,15 @@ void ct_irq_enter(void); > void ct_irq_exit(void); > void ct_irq_enter_irqson(void); > void ct_irq_exit_irqson(void); > +void ct_nmi_enter(void); > +void ct_nmi_exit(void); > #else > static inline void ct_irq_enter(void) { } > static inline void ct_irq_exit(void) { } > static inline void ct_irq_enter_irqson(void) { } > static inline void ct_irq_exit_irqson(void) { } > +static inline void ct_nmi_enter(void) { } > +static inline void ct_nmi_exit(void) { } > #endif > > #endif > diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h > index 76878b357ffa..345cdbe9c1b7 100644 > --- a/include/linux/hardirq.h > +++ b/include/linux/hardirq.h > @@ -124,7 +124,7 @@ extern void rcu_nmi_exit(void); > do { \ > __nmi_enter(); \ > lockdep_hardirq_enter(); \ > - rcu_nmi_enter(); \ > + ct_nmi_enter(); \ > instrumentation_begin(); \ > ftrace_nmi_enter(); \ > instrumentation_end(); \ > @@ -143,7 +143,7 @@ extern void rcu_nmi_exit(void); > instrumentation_begin(); \ > ftrace_nmi_exit(); \ > instrumentation_end(); \ > - rcu_nmi_exit(); \ > + ct_nmi_exit(); \ > lockdep_hardirq_exit(); \ > __nmi_exit(); \ > } while (0) > diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c > index b63ff851472e..1686cd528966 100644 > --- a/kernel/context_tracking.c > +++ b/kernel/context_tracking.c > @@ -267,3 +267,13 @@ void ct_irq_exit_irqson(void) > { > rcu_irq_exit_irqson(); > } > + > +noinstr void ct_nmi_enter(void) > +{ > + rcu_nmi_enter(); > +} > + > +noinstr void ct_nmi_exit(void) > +{ > + rcu_nmi_exit(); > +} > diff --git a/kernel/entry/common.c b/kernel/entry/common.c > index cebc98b8adc6..08230507793f 100644 > --- a/kernel/entry/common.c > +++ b/kernel/entry/common.c > @@ -449,7 +449,7 @@ irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs) > __nmi_enter(); > lockdep_hardirqs_off(CALLER_ADDR0); > lockdep_hardirq_enter(); > - rcu_nmi_enter(); > + ct_nmi_enter(); > > instrumentation_begin(); > trace_hardirqs_off_finish(); > @@ -469,7 +469,7 @@ void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state) > } > instrumentation_end(); > > - rcu_nmi_exit(); > + ct_nmi_exit(); > lockdep_hardirq_exit(); > if (irq_state.lockdep) > lockdep_hardirqs_on(CALLER_ADDR0); > diff --git a/kernel/extable.c b/kernel/extable.c > index b6f330f0fe74..88d4d739c5a1 100644 > --- a/kernel/extable.c > +++ b/kernel/extable.c > @@ -113,7 +113,7 @@ int kernel_text_address(unsigned long addr) > > /* Treat this like an NMI as it can happen anywhere */ > if (no_rcu) > - rcu_nmi_enter(); > + ct_nmi_enter(); > > if (is_module_text_address(addr)) > goto out; > @@ -126,7 +126,7 @@ int kernel_text_address(unsigned long addr) > ret = 0; > out: > if (no_rcu) > - rcu_nmi_exit(); > + ct_nmi_exit(); > > return ret; > } > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index 7c500c708180..9434da82af8a 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -3086,7 +3086,7 @@ void __trace_stack(struct trace_array *tr, unsigned int trace_ctx, > } > > /* > - * When an NMI triggers, RCU is enabled via rcu_nmi_enter(), > + * When an NMI triggers, RCU is enabled via ct_nmi_enter(), > * but if the above rcu_is_watching() failed, then the NMI > * triggered someplace critical, and ct_irq_enter() should > * not be called from NMI. > -- > 2.25.1 >