From patchwork Mon Sep 16 22:49:23 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frederic Weisbecker X-Patchwork-Id: 13805817 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 1724916F839; Mon, 16 Sep 2024 22:50:26 +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=1726527027; cv=none; b=S/gFtj0BIVaakXwgFq9hzWRczw27fSuJcrEmvyeTJZZ+XtU14vRECam+/Tfp5AizT+aFjU10QJfEUCzqSbY108Rlh91pW0fyW8fg9AllPEDeYu9jitTFAwVWoRH1y7le6C5EftqSBgNwNOqItbN350QtayDByrJpygCY/a+UvsE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726527027; c=relaxed/simple; bh=XFzJ4mxWd3+ScHM8w2S2c71PfRlHFJW2SZ3NxFYLpjE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fWO5ZwNcFv1oZbYk1FTKazVw7cASOrw5+M5Jw4O/WzQDY5cgoA6qIZe4cx6jYMWWM6446DtVQ7h8xGt9u08TtQfVhOZ/hgd97VvCj4+wZiaUk/OCb0Mti4A6HISwts55ZRq9SOCDwsiqTW/dGhc6l0mCfXFb9NzfWIco15kC/yk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=s4KDWK2A; 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="s4KDWK2A" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3574EC4CEC5; Mon, 16 Sep 2024 22:50:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1726527026; bh=XFzJ4mxWd3+ScHM8w2S2c71PfRlHFJW2SZ3NxFYLpjE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=s4KDWK2AlwUZuNXgLahGqvEaNQPmVCiV0IY7tZZv/XSzapW/LIdDoxD8sYVz8nFGB IV5K59auZaawNpjtMUL8snJKX+XRvWYOG3UpKWoc3RlOHhfXSIOIvg3F2DPN0qpBGB BvObx5Tnx9cSQJTxu9Wg9vkJGXzDgNjIz0jyQd+AoGn3bMR9LaxTr5v99sFYx/vp8g Hks80bjIVhUYW2egV9yZ07DklXSGdx6zi3sCnd36XCQ9dSMPhd9x6odQyXkxVJc1QT h+P6r1dmvZ6jItnY+r/NBGRQBKb0ZleKpRnwrBDC7CTLkYWWqsdTo5orDIAeFz9ajB ya8CZqOKJ4wag== From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , "Paul E. McKenney" , Neeraj Upadhyay , Joel Fernandes , Boqun Feng , Zqiang , rcu@vger.kernel.org, Andrew Morton , Peter Zijlstra , Thomas Gleixner Subject: [PATCH 19/19] rcu: Use kthread preferred affinity for RCU exp kworkers Date: Tue, 17 Sep 2024 00:49:23 +0200 Message-ID: <20240916224925.20540-20-frederic@kernel.org> X-Mailer: git-send-email 2.46.0 In-Reply-To: <20240916224925.20540-1-frederic@kernel.org> References: <20240916224925.20540-1-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 902d4b5abbe7..118477a6dda4 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -4815,6 +4815,22 @@ 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) @@ -4827,7 +4843,7 @@ 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); @@ -4837,16 +4853,9 @@ 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) @@ -4931,79 +4940,6 @@ 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? */ @@ -5032,7 +4968,6 @@ 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); @@ -5249,8 +5184,6 @@ 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;