From patchwork Tue Nov 12 14:22:45 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frederic Weisbecker X-Patchwork-Id: 13872314 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 189F520125E; Tue, 12 Nov 2024 14:23:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731421438; cv=none; b=kEhDjXThjuniwtBqZetx8lStX+MEpgy8hK7p8hX0tRzBtOHjlVJbsTTfu3UO/NYzU4f15SWN90fJTgyfzi4eWpoRQO9Lic7ixsgU+hxSBf9CReWSZk9JZ4tMD0XYGFUWq1dhOuHEXN7/yvQ1YE8PY3FlPCWoY84MSV5ju+Norns= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731421438; c=relaxed/simple; bh=8m8QxthF6RSxr1U64nd88bE97A7JtNoesWKGZhEX7H4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ip7fSfIuv2ESv5PvS3+wB1O29isgJAtXvzquWNQGeKomROCJeX1v30ttzN2qFafJFR0xj9prYqLOT5y9TdIRz8KCJcCZtkaYMJiqlCzg4xMpImcUpfcaIXpHl7C6dK8ERbPURvg7znK9DH3/Jo2uwK89jd+eXtQWBYcsoF+pBZg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YlbTDH6h; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YlbTDH6h" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1974BC4CED0; Tue, 12 Nov 2024 14:23:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1731421438; bh=8m8QxthF6RSxr1U64nd88bE97A7JtNoesWKGZhEX7H4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YlbTDH6hdjV/sk+v9jJccS2ss5qGqRf+KxF7XQl8ZALctCB5jEp/0MmrVg7Qd979/ ol7GkfKe91I9vcGVLZgBHr6E/vDNTbeYge+EXau2BMs7xU6PvYXVeMzLKdtl+xGmHf YKsp1VJuOnlD5z+BGrK4xHzxTCkGkeF69ybUwYPUKBPsqE4qqHLT4PJoQCY1oESWLh 9sROp5Unh6+hKuw8N8WiPaR37e2Rbr4QQ+kmGHTRQZbBiGuz1Vp3YXlWJIW1xWA5V3 CfHXXnjdx+D/R2oO7Pwxpwy27AjWchCfoHdO1PGf7//Spl0+iQKuC0D8Otg8ScffVe umK1Eh10JAgrA== From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , "Paul E. McKenney" , Uladzislau Rezki , Neeraj Upadhyay , Joel Fernandes , Boqun Feng , Zqiang , rcu@vger.kernel.org, Andrew Morton , Peter Zijlstra , Thomas Gleixner , Michal Hocko , Vlastimil Babka Subject: [PATCH 21/21] rcu: Use kthread preferred affinity for RCU exp kworkers Date: Tue, 12 Nov 2024 15:22:45 +0100 Message-ID: <20241112142248.20503-22-frederic@kernel.org> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20241112142248.20503-1-frederic@kernel.org> References: <20241112142248.20503-1-frederic@kernel.org> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Now that kthreads have an infrastructure to handle preferred affinity against CPU hotplug and housekeeping cpumask, convert RCU exp workers to use it instead of handling all the constraints by itself. Acked-by: Paul E. McKenney Signed-off-by: Frederic Weisbecker --- kernel/rcu/tree.c | 105 +++++++++------------------------------------- 1 file changed, 19 insertions(+), 86 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 65072deb538e..35949ec1f935 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -4891,6 +4891,22 @@ rcu_boot_init_percpu_data(int cpu) rcu_boot_init_nocb_percpu_data(rdp); } +static void rcu_thread_affine_rnp(struct task_struct *t, struct rcu_node *rnp) +{ + cpumask_var_t affinity; + int cpu; + + if (!zalloc_cpumask_var(&affinity, GFP_KERNEL)) + return; + + for_each_leaf_node_possible_cpu(rnp, cpu) + cpumask_set_cpu(cpu, affinity); + + kthread_affine_preferred(t, affinity); + + free_cpumask_var(affinity); +} + struct kthread_worker *rcu_exp_gp_kworker; static void rcu_spawn_exp_par_gp_kworker(struct rcu_node *rnp) @@ -4903,7 +4919,7 @@ static void rcu_spawn_exp_par_gp_kworker(struct rcu_node *rnp) if (rnp->exp_kworker) return; - kworker = kthread_run_worker(0, name, rnp_index); + kworker = kthread_create_worker(0, name, rnp_index); if (IS_ERR_OR_NULL(kworker)) { pr_err("Failed to create par gp kworker on %d/%d\n", rnp->grplo, rnp->grphi); @@ -4913,16 +4929,9 @@ static void rcu_spawn_exp_par_gp_kworker(struct rcu_node *rnp) if (IS_ENABLED(CONFIG_RCU_EXP_KTHREAD)) sched_setscheduler_nocheck(kworker->task, SCHED_FIFO, ¶m); -} -static struct task_struct *rcu_exp_par_gp_task(struct rcu_node *rnp) -{ - struct kthread_worker *kworker = READ_ONCE(rnp->exp_kworker); - - if (!kworker) - return NULL; - - return kworker->task; + rcu_thread_affine_rnp(kworker->task, rnp); + wake_up_process(kworker->task); } static void __init rcu_start_exp_gp_kworker(void) @@ -5007,79 +5016,6 @@ int rcutree_prepare_cpu(unsigned int cpu) return 0; } -static void rcu_thread_affine_rnp(struct task_struct *t, struct rcu_node *rnp) -{ - cpumask_var_t affinity; - int cpu; - - if (!zalloc_cpumask_var(&affinity, GFP_KERNEL)) - return; - - for_each_leaf_node_possible_cpu(rnp, cpu) - cpumask_set_cpu(cpu, affinity); - - kthread_affine_preferred(t, affinity); - - free_cpumask_var(affinity); -} - -/* - * Update kthreads affinity during CPU-hotplug changes. - * - * Set the per-rcu_node kthread's affinity to cover all CPUs that are - * served by the rcu_node in question. The CPU hotplug lock is still - * held, so the value of rnp->qsmaskinit will be stable. - * - * We don't include outgoingcpu in the affinity set, use -1 if there is - * no outgoing CPU. If there are no CPUs left in the affinity set, - * this function allows the kthread to execute on any CPU. - * - * Any future concurrent calls are serialized via ->kthread_mutex. - */ -static void rcutree_affinity_setting(unsigned int cpu, int outgoingcpu) -{ - cpumask_var_t cm; - unsigned long mask; - struct rcu_data *rdp; - struct rcu_node *rnp; - struct task_struct *task_exp; - - rdp = per_cpu_ptr(&rcu_data, cpu); - rnp = rdp->mynode; - - task_exp = rcu_exp_par_gp_task(rnp); - - /* - * If CPU is the boot one, this task is created later from early - * initcall since kthreadd must be created first. - */ - if (!task_exp) - return; - - if (!zalloc_cpumask_var(&cm, GFP_KERNEL)) - return; - - mutex_lock(&rnp->kthread_mutex); - mask = rcu_rnp_online_cpus(rnp); - for_each_leaf_node_possible_cpu(rnp, cpu) - if ((mask & leaf_node_cpu_bit(rnp, cpu)) && - cpu != outgoingcpu) - cpumask_set_cpu(cpu, cm); - cpumask_and(cm, cm, housekeeping_cpumask(HK_TYPE_RCU)); - if (cpumask_empty(cm)) { - cpumask_copy(cm, housekeeping_cpumask(HK_TYPE_RCU)); - if (outgoingcpu >= 0) - cpumask_clear_cpu(outgoingcpu, cm); - } - - if (task_exp) - set_cpus_allowed_ptr(task_exp, cm); - - mutex_unlock(&rnp->kthread_mutex); - - free_cpumask_var(cm); -} - /* * Has the specified (known valid) CPU ever been fully online? */ @@ -5108,7 +5044,6 @@ int rcutree_online_cpu(unsigned int cpu) if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) return 0; /* Too early in boot for scheduler work. */ sync_sched_exp_online_cleanup(cpu); - rcutree_affinity_setting(cpu, -1); // Stop-machine done, so allow nohz_full to disable tick. tick_dep_clear(TICK_DEP_BIT_RCU); @@ -5325,8 +5260,6 @@ int rcutree_offline_cpu(unsigned int cpu) rnp->ffmask &= ~rdp->grpmask; raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - rcutree_affinity_setting(cpu, cpu); - // nohz_full CPUs need the tick for stop-machine to work quickly tick_dep_set(TICK_DEP_BIT_RCU); return 0;