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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 81246C4332F for ; Tue, 19 Apr 2022 00:00:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236379AbiDSADD (ORCPT ); Mon, 18 Apr 2022 20:03:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44914 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236116AbiDSAC6 (ORCPT ); Mon, 18 Apr 2022 20:02:58 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6DC2111C3F; Mon, 18 Apr 2022 17:00:17 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id D5BA96123D; Tue, 19 Apr 2022 00:00:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 39513C385A1; Tue, 19 Apr 2022 00:00:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1650326416; bh=3PHr6DaJm3KpAi0VoxU2Z4Urf23rCyOQHDJiKZI+ijM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sGet6K9vISgKGjn1gS6P1dcO4kA+em3X3NGknBPDrM8g6pTs/v4MrfdShT6NJtaEh a+MrX7faiqb7QF4jamJwhFlmvld3MxR5wcOSnDBJjcFFWi0JN31QI3chf0rrHF1FBA XW7TtAspSmObUrE388VxRCdqdDWAK9dORLe4nfGRJynRCyHvA4BJxzl6Av6Gk1UuZg eG3lY7scaX8nfyAZvqIA7IoYiX8N0yKx/reQoypmfmtP2erRQ0OIBujfRIvuzeLgBz YLbVyJEGJ2LcD2zRfi987OCcRNWsv3PSh5fW7vLd7Fs6NdSreK3ppt9offb2lwuNIX y60smg8R3tYCg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id DB7245C0848; Mon, 18 Apr 2022 17:00:15 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, Sebastian Andrzej Siewior , "Paul E . McKenney" Subject: [PATCH rcu 3/9] rcu-tasks: Use rcuwait for the rcu_tasks_kthread() Date: Mon, 18 Apr 2022 17:00:08 -0700 Message-Id: <20220419000014.3948512-3-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20220419000007.GA3945818@paulmck-ThinkPad-P17-Gen-1> References: <20220419000007.GA3945818@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: Sebastian Andrzej Siewior The waitqueue used by rcu_tasks_kthread() has always only one waiter. With a guaranteed only one waiter, this can be replaced with rcuwait which is smaller and simpler. With rcuwait based wake counterpart, the irqwork function (call_rcu_tasks_iw_wakeup()) can be invoked hardirq context because it is only a wake up and no sleeping locks are involved (unlike the wait_queue_head). As a side effect, this is also one piece of the puzzle to pass the RCU selftest at early boot on PREEMPT_RT. Replace wait_queue_head with rcuwait and let the irqwork run in hardirq context on PREEMPT_RT. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Paul E. McKenney --- kernel/rcu/tasks.h | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 76799c81d4be..4b91cb214ca7 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -46,7 +46,7 @@ struct rcu_tasks_percpu { /** * struct rcu_tasks - Definition for a Tasks-RCU-like mechanism. - * @cbs_wq: Wait queue allowing new callback to get kthread's attention. + * @cbs_wait: RCU wait allowing a new callback to get kthread's attention. * @cbs_gbl_lock: Lock protecting callback list. * @kthread_ptr: This flavor's grace-period/callback-invocation kthread. * @gp_func: This flavor's grace-period-wait function. @@ -77,7 +77,7 @@ struct rcu_tasks_percpu { * @kname: This flavor's kthread name. */ struct rcu_tasks { - struct wait_queue_head cbs_wq; + struct rcuwait cbs_wait; raw_spinlock_t cbs_gbl_lock; int gp_state; int gp_sleep; @@ -113,11 +113,11 @@ static void call_rcu_tasks_iw_wakeup(struct irq_work *iwp); #define DEFINE_RCU_TASKS(rt_name, gp, call, n) \ static DEFINE_PER_CPU(struct rcu_tasks_percpu, rt_name ## __percpu) = { \ .lock = __RAW_SPIN_LOCK_UNLOCKED(rt_name ## __percpu.cbs_pcpu_lock), \ - .rtp_irq_work = IRQ_WORK_INIT(call_rcu_tasks_iw_wakeup), \ + .rtp_irq_work = IRQ_WORK_INIT_HARD(call_rcu_tasks_iw_wakeup), \ }; \ static struct rcu_tasks rt_name = \ { \ - .cbs_wq = __WAIT_QUEUE_HEAD_INITIALIZER(rt_name.cbs_wq), \ + .cbs_wait = __RCUWAIT_INITIALIZER(rt_name.wait), \ .cbs_gbl_lock = __RAW_SPIN_LOCK_UNLOCKED(rt_name.cbs_gbl_lock), \ .gp_func = gp, \ .call_func = call, \ @@ -266,7 +266,7 @@ static void call_rcu_tasks_iw_wakeup(struct irq_work *iwp) struct rcu_tasks_percpu *rtpcp = container_of(iwp, struct rcu_tasks_percpu, rtp_irq_work); rtp = rtpcp->rtpp; - wake_up(&rtp->cbs_wq); + rcuwait_wake_up(&rtp->cbs_wait); } // Enqueue a callback for the specified flavor of Tasks RCU. @@ -514,7 +514,9 @@ static int __noreturn rcu_tasks_kthread(void *arg) set_tasks_gp_state(rtp, RTGS_WAIT_CBS); /* If there were none, wait a bit and start over. */ - wait_event_idle(rtp->cbs_wq, (needgpcb = rcu_tasks_need_gpcb(rtp))); + rcuwait_wait_event(&rtp->cbs_wait, + (needgpcb = rcu_tasks_need_gpcb(rtp)), + TASK_IDLE); if (needgpcb & 0x2) { // Wait for one grace period. -- 2.31.1.189.g2e36527f23