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=-16.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNWANTED_LANGUAGE_BODY, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 BB26CC433B4 for ; Tue, 11 May 2021 23:03:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 997E161925 for ; Tue, 11 May 2021 23:03:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230379AbhEKXFF (ORCPT ); Tue, 11 May 2021 19:05:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:42546 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230104AbhEKXEq (ORCPT ); Tue, 11 May 2021 19:04:46 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id EEB886193E; Tue, 11 May 2021 23:03:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1620774219; bh=pnNo0+6CoC3Y3VXKvc+NLxvvGAuYk+/zPk5hHwrQLjg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FIfzuatAT8Xw2hgW3CytMy5KGg37mk0YMO9MsuH347B5BfOpxfMzu1mWlXhQPf67x gpCpCiAqNVgP0IDumgls5MQfLcsygU5phEBnNXiLzIOufJcV7gm7ODyPD+NtlkFRbh 82d9EBr4VXNxJuee3fcEEQW3VLsORfmCTOqbvXxfgWLrk1q+8N9+vAb6njgzRAePBX OrUWdxjy8EL6VMXW8itFK+2Ov5+AtHzkJsZ1ouFzgv29DeerbkE0KayFOql5d0LzrR aecv5VAeMFeEuNQcCnFtLNy8WwlJ8LYso1V7gg9J74InJwewl4EyyU/33vfueqZVd6 u8z2q8c4/M/HQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 673325C0DE5; Tue, 11 May 2021 16:03:38 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, Frederic Weisbecker , Neeraj Upadhyay , Boqun Feng , "Paul E . McKenney" Subject: [PATCH tip/core/rcu 08/10] rcu/nocb: Prepare for fine-grained deferred wakeup Date: Tue, 11 May 2021 16:03:34 -0700 Message-Id: <20210511230336.2894314-8-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20210511230244.GA2894061@paulmck-ThinkPad-P17-Gen-1> References: <20210511230244.GA2894061@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Frederic Weisbecker Tuning the deferred wakeup level must be done from a safe wakeup point. Currently those sites are: * ->nocb_timer * user/idle/guest entry * CPU down * softirq/rcuc All of these sites perform the wake up for both RCU_NOCB_WAKE and RCU_NOCB_WAKE_FORCE. In order to merge ->nocb_timer and ->nocb_bypass_timer together, we plan to add a new RCU_NOCB_WAKE_BYPASS that really should be deferred until a timer fires so that we don't wake up the NOCB-gp kthread too early. To prepare for that, this commit specifies the per-callsite wakeup level/limit. Cc: Josh Triplett Cc: Lai Jiangshan Cc: Joel Fernandes Cc: Neeraj Upadhyay Cc: Boqun Feng Signed-off-by: Frederic Weisbecker [ paulmck: Fix non-NOCB rcu_nocb_need_deferred_wakeup() definition. ] Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 2 +- kernel/rcu/tree.h | 2 +- kernel/rcu/tree_plugin.h | 17 +++++++++-------- 3 files changed, 11 insertions(+), 10 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 8e78b2430c16..5f1545aab9ed 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3911,7 +3911,7 @@ static int rcu_pending(int user) check_cpu_stall(rdp); /* Does this CPU need a deferred NOCB wakeup? */ - if (rcu_nocb_need_deferred_wakeup(rdp)) + if (rcu_nocb_need_deferred_wakeup(rdp, RCU_NOCB_WAKE)) return 1; /* Is this a nohz_full CPU in userspace or idle? (Ignore RCU if so.) */ diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index b280a843bd2c..2510e86265c1 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -433,7 +433,7 @@ static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp, bool *was_alldone, unsigned long flags); static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty, unsigned long flags); -static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp); +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level); static bool do_nocb_deferred_wakeup(struct rcu_data *rdp); static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); static void rcu_spawn_cpu_nocb_kthread(int cpu); diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index db28e3123f32..e2e5e4968f43 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2352,13 +2352,14 @@ static int rcu_nocb_cb_kthread(void *arg) } /* Is a deferred wakeup of rcu_nocb_kthread() required? */ -static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level) { - return READ_ONCE(rdp->nocb_defer_wakeup) > RCU_NOCB_WAKE_NOT; + return READ_ONCE(rdp->nocb_defer_wakeup) >= level; } /* Do a deferred wakeup of rcu_nocb_kthread(). */ -static bool do_nocb_deferred_wakeup_common(struct rcu_data *rdp) +static bool do_nocb_deferred_wakeup_common(struct rcu_data *rdp, + int level) { unsigned long flags; int ndw; @@ -2367,7 +2368,7 @@ static bool do_nocb_deferred_wakeup_common(struct rcu_data *rdp) raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags); - if (!rcu_nocb_need_deferred_wakeup(rdp_gp)) { + if (!rcu_nocb_need_deferred_wakeup(rdp_gp, level)) { raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags); return false; } @@ -2384,7 +2385,7 @@ static void do_nocb_deferred_wakeup_timer(struct timer_list *t) { struct rcu_data *rdp = from_timer(rdp, t, nocb_timer); - do_nocb_deferred_wakeup_common(rdp); + do_nocb_deferred_wakeup_common(rdp, RCU_NOCB_WAKE); } /* @@ -2397,8 +2398,8 @@ static bool do_nocb_deferred_wakeup(struct rcu_data *rdp) if (!rdp->nocb_gp_rdp) return false; - if (rcu_nocb_need_deferred_wakeup(rdp->nocb_gp_rdp)) - return do_nocb_deferred_wakeup_common(rdp); + if (rcu_nocb_need_deferred_wakeup(rdp->nocb_gp_rdp, RCU_NOCB_WAKE)) + return do_nocb_deferred_wakeup_common(rdp, RCU_NOCB_WAKE); return false; } @@ -2939,7 +2940,7 @@ static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) { } -static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level) { return false; } -- 2.31.1.189.g2e36527f23