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=-10.3 required=3.0 tests=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 DE7DAC433DF for ; Wed, 13 May 2020 16:47:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3F07C207D4 for ; Wed, 13 May 2020 16:47:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589388465; bh=XdTU1QCu9wvEeudPrv5d5VVXBttCnEKZypaCKnPJKU4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=csh1CsDOwp4h7EePEigIGB9DWBwosHrt3CXw8oLNyUiQ5bcDE7CMoSbH/j9o3WAQZ SVhJH9P1SEeMVUoe8nxGLGFGtrYRPktv6tgEPWkfhLF7mKsk8bCNdfDBlxIFTm0bpB ypxr2+3HDwMhYghFMgIlIusNP+FtW9np9oLo258o= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389795AbgEMQro (ORCPT ); Wed, 13 May 2020 12:47:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:53670 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389771AbgEMQrh (ORCPT ); Wed, 13 May 2020 12:47:37 -0400 Received: from lenoir.home (lfbn-ncy-1-985-231.w90-101.abo.wanadoo.fr [90.101.63.231]) (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 B0650207D8; Wed, 13 May 2020 16:47:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589388457; bh=XdTU1QCu9wvEeudPrv5d5VVXBttCnEKZypaCKnPJKU4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jtSLr2i3TNN/6yMMyqC61pPjQTM08T08C7zTe8V2jYq4/uV4RrYxFEB7drnIF5xM4 YI5vL0HBSmeB8NvpCAFZDp3W0E2NybF3Rb33drdQnlgl7zv8o1l158RRdtMmdAC8ER 7vL9mJlK3tdmlxjMJWlRJbIzDLta55PL+8hqjKQ8= From: Frederic Weisbecker To: "Paul E . McKenney" Cc: LKML , Frederic Weisbecker , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , Josh Triplett Subject: [PATCH 09/10] rcu: Allow to re-offload a CPU that used to be nocb Date: Wed, 13 May 2020 18:47:13 +0200 Message-Id: <20200513164714.22557-10-frederic@kernel.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200513164714.22557-1-frederic@kernel.org> References: <20200513164714.22557-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is essentially the reverse operation of de-offloading. For now it's only supported on CPUs that used to be offloaded and therefore still have the relevant nocb_cb/nocb_gp kthreads around. 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 --- include/linux/rcupdate.h | 2 ++ kernel/rcu/tree_plugin.h | 44 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 46 insertions(+) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 1d3a4c37c3c1..ee95e49d675f 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -96,9 +96,11 @@ static inline void rcu_user_exit(void) { } #ifdef CONFIG_RCU_NOCB_CPU void rcu_init_nohz(void); +void rcu_nocb_cpu_offload(int cpu); void rcu_nocb_cpu_deoffload(int cpu); #else /* #ifdef CONFIG_RCU_NOCB_CPU */ static inline void rcu_init_nohz(void) { } +static inline void rcu_nocb_cpu_offload(int cpu) { } static inline void rcu_nocb_cpu_deoffload(int cpu) { } #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index c74a4df8d5f2..ae4b5e9f2fc5 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2224,6 +2224,50 @@ void rcu_nocb_cpu_deoffload(int cpu) mutex_unlock(&rcu_state.barrier_mutex); } +static void __rcu_nocb_rdp_offload(struct rcu_data *rdp) +{ + unsigned long flags; + struct rcu_node *rnp = rdp->mynode; + + printk("Offloading %d\n", rdp->cpu); + + raw_spin_lock_irqsave(&rdp->nocb_lock, flags); + raw_spin_lock_rcu_node(rnp); + rcu_segcblist_offload(&rdp->cblist, true); + raw_spin_unlock_rcu_node(rnp); + raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags); + + kthread_unpark(rdp->nocb_cb_kthread); +} + +static long rcu_nocb_rdp_offload(void *arg) +{ + struct rcu_data *rdp = arg; + + WARN_ON_ONCE(rdp->cpu != raw_smp_processor_id()); + __rcu_nocb_rdp_offload(rdp); + + return 0; +} + +void rcu_nocb_cpu_offload(int cpu) +{ + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + + mutex_lock(&rcu_state.barrier_mutex); + cpus_read_lock(); + if (!rcu_segcblist_is_offloaded(&rdp->cblist) && rdp->nocb_cb_kthread) { + if (cpu_online(cpu)) { + work_on_cpu(cpu, rcu_nocb_rdp_offload, rdp); + } else { + __rcu_nocb_rdp_offload(rdp); + } + cpumask_set_cpu(cpu, rcu_nocb_mask); + } + cpus_read_unlock(); + mutex_unlock(&rcu_state.barrier_mutex); +} + void __init rcu_init_nohz(void) { int cpu; -- 2.25.0