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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 0AB04C4742C for ; Fri, 13 Nov 2020 12:14:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BD2DA22259 for ; Fri, 13 Nov 2020 12:14:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="EJbZRnsB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726822AbgKMMOL (ORCPT ); Fri, 13 Nov 2020 07:14:11 -0500 Received: from mail.kernel.org ([198.145.29.99]:47792 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726789AbgKMMOJ (ORCPT ); Fri, 13 Nov 2020 07:14:09 -0500 Received: from localhost.localdomain (unknown [176.167.84.141]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DB6C822255; Fri, 13 Nov 2020 12:14:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605269648; bh=eLExhSQSXS5B7otxntXzK5K8mPDMaZJX3vIuPHTeUKo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EJbZRnsBbfV+QPwamVPmcu/SsuyB3sCOxIAd7K4OyjC4Z5Zk4ETsf3SjPJ0YHrX9u ZM47SyiYD3qhwayLWfgTPN293zmZWg1gf8OId39VYzDz0xPG9d2m0yI53z4NpDqXmV yfhmlgId8aPUNM9ZlG9A3DKY0URRx3/Xrm2H3n/c= From: Frederic Weisbecker To: "Paul E . McKenney" Cc: LKML , Frederic Weisbecker , Steven Rostedt , Thomas Gleixner , Mathieu Desnoyers , Boqun Feng , Lai Jiangshan , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , rcu@vger.kernel.org Subject: [PATCH 08/19] rcu/nocb: Shutdown nocb timer on de-offloading Date: Fri, 13 Nov 2020 13:13:23 +0100 Message-Id: <20201113121334.166723-9-frederic@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201113121334.166723-1-frederic@kernel.org> References: <20201113121334.166723-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Make sure the nocb timer can't fire anymore before we reach the final de-offload state. Spuriously waking up the GP kthread is no big deal but we must prevent from executing the timer callback without nocb locking. Inspired-by: Paul E. McKenney Signed-off-by: Frederic Weisbecker Cc: Paul E. McKenney Cc: Josh Triplett Cc: Steven Rostedt Cc: Mathieu Desnoyers Cc: Lai Jiangshan Cc: Joel Fernandes Cc: Neeraj Upadhyay Cc: Thomas Gleixner Cc: Boqun Feng --- kernel/rcu/tree.h | 1 + kernel/rcu/tree_plugin.h | 12 +++++++++++- 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index e0deb4829847..5d359b9f9fec 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -257,6 +257,7 @@ struct rcu_data { }; /* Values for nocb_defer_wakeup field in struct rcu_data. */ +#define RCU_NOCB_WAKE_OFF -1 #define RCU_NOCB_WAKE_NOT 0 #define RCU_NOCB_WAKE 1 #define RCU_NOCB_WAKE_FORCE 2 diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 3b4f01a111d8..44b4ab9b3953 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1665,6 +1665,8 @@ static void wake_nocb_gp(struct rcu_data *rdp, bool force, static void wake_nocb_gp_defer(struct rcu_data *rdp, int waketype, const char *reason) { + if (rdp->nocb_defer_wakeup == RCU_NOCB_WAKE_OFF) + return; if (rdp->nocb_defer_wakeup == RCU_NOCB_WAKE_NOT) mod_timer(&rdp->nocb_timer, jiffies + 1); if (rdp->nocb_defer_wakeup < waketype) @@ -2243,7 +2245,7 @@ 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) { - return READ_ONCE(rdp->nocb_defer_wakeup); + return READ_ONCE(rdp->nocb_defer_wakeup) > RCU_NOCB_WAKE_NOT; } /* Do a deferred wakeup of rcu_nocb_kthread(). */ @@ -2337,6 +2339,12 @@ static int __rcu_nocb_rdp_deoffload(struct rcu_data *rdp) swait_event_exclusive(rdp->nocb_state_wq, !rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB | SEGCBLIST_KTHREAD_GP)); + /* Make sure nocb timer won't stay around */ + rcu_nocb_lock_irqsave(rdp, flags); + WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_OFF); + rcu_nocb_unlock_irqrestore(rdp, flags); + del_timer_sync(&rdp->nocb_timer); + return ret; } @@ -2393,6 +2401,8 @@ static int __rcu_nocb_rdp_offload(struct rcu_data *rdp) * SEGCBLIST_SOFTIRQ_ONLY mode. */ raw_spin_lock_irqsave(&rdp->nocb_lock, flags); + /* Re-enable nocb timer */ + WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT); /* * We didn't take the nocb lock while working on the * rdp->cblist in SEGCBLIST_SOFTIRQ_ONLY mode. -- 2.25.1