From patchwork Mon Jun 20 23:10:25 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 12888560 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 106E4CCA480 for ; Mon, 20 Jun 2022 23:15:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346912AbiFTXPT (ORCPT ); Mon, 20 Jun 2022 19:15:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55948 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1347120AbiFTXMG (ORCPT ); Mon, 20 Jun 2022 19:12:06 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A9638222A5; Mon, 20 Jun 2022 16:10:45 -0700 (PDT) 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 dfw.source.kernel.org (Postfix) with ESMTPS id 90C7561515; Mon, 20 Jun 2022 23:10:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 55D7AC341EF; Mon, 20 Jun 2022 23:10:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1655766632; bh=xl4Qv/D8eO08gmDd70pGOWhnlkzRN6HwvsTr8ErlRVs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PeJnwQLjb2yr4ZKchVmSDjcE/5bVBREF2ju+diiQNUrbqfyWJJYCOScGoWeCatTlA +p50b69yLyT9aVH0DCMwVi4A00NrVzILftBP23XTuRorgdNKQLMDyMWOUvjwLyE9uW cG6nuvxpSYN0FdUsvkXBAB1xqzp7Ppy4jFO7IOL7hDD/5clVvVfEnt3YLjjmULdLIG yNTQIcStxJspHy9+66VYx3rAkLvhlKAcA6WFg3MtuJ2qbw8bRA5ZPlwYsqcu0VEXLa qtVKzOE5U1/FuitQavSKjnlIJ6Zh0tQc2CZXpOAqDgr6qHZHVrlkYo3akrVS+2JBgB g/hhMMvXl1YnQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 71F0A5C11DB; Mon, 20 Jun 2022 16:10:31 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, Frederic Weisbecker , Peter Zijlstra , Thomas Gleixner , Neeraj Upadhyay , Uladzislau Rezki , Joel Fernandes , Boqun Feng , Nicolas Saenz Julienne , Marcelo Tosatti , Xiongfeng Wang , Yu Liao , Phil Auld , Paul Gortmaker , Alex Belits , "Paul E . McKenney" Subject: [PATCH rcu 19/23] rcu/context-tracking: Remove unused and/or unecessary middle functions Date: Mon, 20 Jun 2022 16:10:25 -0700 Message-Id: <20220620231029.3844583-19-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20220620231027.GA3844372@paulmck-ThinkPad-P17-Gen-1> References: <20220620231027.GA3844372@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: Frederic Weisbecker Some eqs functions are now only used internally by context tracking, so their public declarations can be removed. Also middle functions such as rcu_user_*() and rcu_idle_*() which now directly call to rcu_eqs_enter() and rcu_eqs_exit() can be wiped out as well. Signed-off-by: Frederic Weisbecker 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 Signed-off-by: Paul E. McKenney --- Documentation/RCU/stallwarn.rst | 2 +- include/linux/hardirq.h | 8 --- include/linux/rcupdate.h | 8 --- include/linux/rcutiny.h | 2 - include/linux/rcutree.h | 2 - kernel/context_tracking.c | 98 +++++++++------------------------ 6 files changed, 28 insertions(+), 92 deletions(-) diff --git a/Documentation/RCU/stallwarn.rst b/Documentation/RCU/stallwarn.rst index ce1f58a9d954b..e38c587067fc8 100644 --- a/Documentation/RCU/stallwarn.rst +++ b/Documentation/RCU/stallwarn.rst @@ -97,7 +97,7 @@ warnings: which will include additional debugging information. - A low-level kernel issue that either fails to invoke one of the - variants of rcu_user_enter(), rcu_user_exit(), ct_idle_enter(), + variants of rcu_eqs_enter(true), rcu_eqs_exit(true), ct_idle_enter(), ct_idle_exit(), ct_irq_enter(), or ct_irq_exit() on the one hand, or that invokes one of them too many times on the other. Historically, the most frequent issue has been an omission diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index 345cdbe9c1b70..d57cab4d4c06f 100644 --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -92,14 +92,6 @@ void irq_exit_rcu(void); #define arch_nmi_exit() do { } while (0) #endif -#ifdef CONFIG_TINY_RCU -static inline void rcu_nmi_enter(void) { } -static inline void rcu_nmi_exit(void) { } -#else -extern void rcu_nmi_enter(void); -extern void rcu_nmi_exit(void); -#endif - /* * NMI vs Tracing * -------------- diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 3717cad983a67..434da1eb88cd9 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -104,14 +104,6 @@ static inline void rcu_sysrq_start(void) { } static inline void rcu_sysrq_end(void) { } #endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */ -#ifdef CONFIG_NO_HZ_FULL -void rcu_user_enter(void); -void rcu_user_exit(void); -#else -static inline void rcu_user_enter(void) { } -static inline void rcu_user_exit(void) { } -#endif /* CONFIG_NO_HZ_FULL */ - #if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK)) void rcu_irq_work_resched(void); #else diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index 591119413cf1d..900ba35c3582d 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -76,8 +76,6 @@ static inline int rcu_needs_cpu(void) static inline void rcu_virt_note_context_switch(int cpu) { } static inline void rcu_cpu_stall_reset(void) { } static inline int rcu_jiffies_till_stall_check(void) { return 21 * HZ; } -static inline void rcu_idle_enter(void) { } -static inline void rcu_idle_exit(void) { } static inline void rcu_irq_exit_check_preempt(void) { } #define rcu_is_idle_cpu(cpu) \ (is_idle_task(current) && !in_nmi() && !in_hardirq() && !in_serving_softirq()) diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 24db1e41695c8..9cca00ed9bc9f 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -45,8 +45,6 @@ unsigned long start_poll_synchronize_rcu(void); bool poll_state_synchronize_rcu(unsigned long oldstate); void cond_synchronize_rcu(unsigned long oldstate); -void rcu_idle_enter(void); -void rcu_idle_exit(void); bool rcu_is_idle_cpu(int cpu); #ifdef CONFIG_PROVE_RCU diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index f3e92705e0a89..8b0979412f755 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -189,17 +189,17 @@ static void noinstr rcu_eqs_exit(bool user) } /** - * rcu_nmi_exit - inform RCU of exit from NMI context + * ct_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 ct->dynticks and ct->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(), be sure to test + * If you add or remove a call to ct_nmi_exit(), be sure to test * with CONFIG_RCU_EQS_DEBUG=y. */ -void noinstr rcu_nmi_exit(void) +void noinstr ct_nmi_exit(void) { struct context_tracking *ct = this_cpu_ptr(&context_tracking); @@ -242,7 +242,7 @@ void noinstr rcu_nmi_exit(void) } /** - * rcu_nmi_enter - inform RCU of entry to NMI context + * ct_nmi_enter - inform RCU of entry to NMI context * * If the CPU was idle from RCU's viewpoint, update ct->dynticks and * ct->dynticks_nmi_nesting to let the RCU grace-period handling know @@ -250,10 +250,10 @@ void noinstr rcu_nmi_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(), be sure to test + * If you add or remove a call to ct_nmi_enter(), be sure to test * with CONFIG_RCU_EQS_DEBUG=y. */ -void noinstr rcu_nmi_enter(void) +void noinstr ct_nmi_enter(void) { long incby = 2; struct context_tracking *ct = this_cpu_ptr(&context_tracking); @@ -302,32 +302,33 @@ void noinstr rcu_nmi_enter(void) } /** - * rcu_idle_enter - inform RCU that current CPU is entering idle + * ct_idle_enter - inform RCU that current CPU is entering idle * * Enter idle mode, in other words, -leave- the mode in which RCU * read-side critical sections can occur. (Though RCU read-side * critical sections can occur in irq handlers in idle, a possibility * handled by irq_enter() and irq_exit().) * - * If you add or remove a call to rcu_idle_enter(), be sure to test with + * If you add or remove a call to ct_idle_enter(), be sure to test with * CONFIG_RCU_EQS_DEBUG=y. */ -void noinstr rcu_idle_enter(void) +void noinstr ct_idle_enter(void) { WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !raw_irqs_disabled()); rcu_eqs_enter(false); } +EXPORT_SYMBOL_GPL(ct_idle_enter); /** - * rcu_idle_exit - inform RCU that current CPU is leaving idle + * ct_idle_exit - inform RCU that current CPU is leaving idle * * Exit idle mode, in other words, -enter- the mode in which RCU * read-side critical sections can occur. * - * If you add or remove a call to rcu_idle_exit(), be sure to test with + * If you add or remove a call to ct_idle_exit(), be sure to test with * CONFIG_RCU_EQS_DEBUG=y. */ -void noinstr rcu_idle_exit(void) +void noinstr ct_idle_exit(void) { unsigned long flags; @@ -335,18 +336,6 @@ void noinstr rcu_idle_exit(void) rcu_eqs_exit(false); raw_local_irq_restore(flags); } -EXPORT_SYMBOL_GPL(rcu_idle_exit); - -noinstr void ct_idle_enter(void) -{ - rcu_idle_enter(); -} -EXPORT_SYMBOL_GPL(ct_idle_enter); - -void ct_idle_exit(void) -{ - rcu_idle_exit(); -} EXPORT_SYMBOL_GPL(ct_idle_exit); /** @@ -431,50 +420,11 @@ void ct_irq_exit_irqson(void) ct_irq_exit(); local_irq_restore(flags); } - -noinstr void ct_nmi_enter(void) -{ - rcu_nmi_enter(); -} - -noinstr void ct_nmi_exit(void) -{ - rcu_nmi_exit(); -} +#else +static __always_inline void rcu_eqs_enter(bool user) { } +static __always_inline void rcu_eqs_exit(bool user) { } #endif /* #ifdef CONFIG_CONTEXT_TRACKING_IDLE */ -#ifdef CONFIG_NO_HZ_FULL -/** - * rcu_user_enter - inform RCU that we are resuming userspace. - * - * Enter RCU idle mode right before resuming userspace. No use of RCU - * is permitted between this call and rcu_user_exit(). This way the - * CPU doesn't need to maintain the tick for RCU maintenance purposes - * when the CPU runs in userspace. - * - * If you add or remove a call to rcu_user_enter(), be sure to test with - * CONFIG_RCU_EQS_DEBUG=y. - */ -noinstr void rcu_user_enter(void) -{ - rcu_eqs_enter(true); -} - -/** - * rcu_user_exit - inform RCU that we are exiting userspace. - * - * Exit RCU idle mode while entering the kernel because it can - * run a RCU read side critical section anytime. - * - * If you add or remove a call to rcu_user_exit(), be sure to test with - * CONFIG_RCU_EQS_DEBUG=y. - */ -void noinstr rcu_user_exit(void) -{ - rcu_eqs_exit(true); -} -#endif /* #ifdef CONFIG_NO_HZ_FULL */ - #ifdef CONFIG_CONTEXT_TRACKING_USER #define CREATE_TRACE_POINTS @@ -542,7 +492,13 @@ void noinstr __ct_user_enter(enum ctx_state state) * that will fire and reschedule once we resume in user/guest mode. */ rcu_irq_work_resched(); - rcu_user_enter(); + /* + * Enter RCU idle mode right before resuming userspace. No use of RCU + * is permitted between this call and rcu_eqs_exit(). This way the + * CPU doesn't need to maintain the tick for RCU maintenance purposes + * when the CPU runs in userspace. + */ + rcu_eqs_enter(true); } /* * Even if context tracking is disabled on this CPU, because it's outside @@ -579,7 +535,7 @@ void ct_user_enter(enum ctx_state state) /* * Some contexts may involve an exception occuring in an irq, * leading to that nesting: - * ct_irq_enter() rcu_user_exit() rcu_user_exit() ct_irq_exit() + * ct_irq_enter() rcu_eqs_exit(true) rcu_eqs_enter(true) ct_irq_exit() * This would mess up the dyntick_nesting count though. And rcu_irq_*() * helpers are enough to protect RCU uses inside the exception. So * just return immediately if we detect we are in an IRQ. @@ -631,10 +587,10 @@ void noinstr __ct_user_exit(enum ctx_state state) if (__this_cpu_read(context_tracking.state) == state) { if (__this_cpu_read(context_tracking.active)) { /* - * We are going to run code that may use RCU. Inform - * RCU core about that (ie: we may need the tick again). + * Exit RCU idle mode while entering the kernel because it can + * run a RCU read side critical section anytime. */ - rcu_user_exit(); + rcu_eqs_exit(true); if (state == CONTEXT_USER) { instrumentation_begin(); vtime_user_exit(current);