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 BBAA1C433F5 for ; Mon, 18 Apr 2022 22:55:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234201AbiDRW53 (ORCPT ); Mon, 18 Apr 2022 18:57:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44392 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233519AbiDRW4t (ORCPT ); Mon, 18 Apr 2022 18:56:49 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D86562D1CA; Mon, 18 Apr 2022 15:54:05 -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 ams.source.kernel.org (Postfix) with ESMTPS id CC07CB81147; Mon, 18 Apr 2022 22:54:03 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1A7AC385B8; Mon, 18 Apr 2022 22:54:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1650322441; bh=hgEd3cpLsRyZZOBZzaKl/DvFtkkxfVr47Q/gsMtP94Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fIwQHmfCQMiJX9gTWhnRiYrGeGRiAjSnmKfKNwTX3T8czHIPfXHr20hQj4H4RIV3Z 5+ikJZSPNMdE0p+FEq9BR/D+Dn8IsDp5na/wlQAWlR+R4StiOrff1O+nkjBVxTFqNl M42Ap8B38iWEo2feWC8XVIFDcliBrq/tMK2AuVYPwfTdhboYt0/on7ejp6W6yHg4NW YIzNXuPfYq/16AgqG5nCLTIhI3J+nOCMj7tcLwLLDMc1yVr0XnrEtSlERZlHTsQBhI 8EZHd7b0BDx7d6DrGd6HTNBpxtcsHdE2bKDYpFvObzSReN88mfq8excuSUkZ5DzHtc rxLMARwgOE+YQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id F20BD5C1355; Mon, 18 Apr 2022 15:54:00 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, Zqiang , "Paul E . McKenney" Subject: [PATCH rcu 11/11] rcu: Use IRQ_WORK_INIT_HARD() to avoid rcu_read_unlock() hangs Date: Mon, 18 Apr 2022 15:53:59 -0700 Message-Id: <20220418225359.3945217-11-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20220418225345.GA3945110@paulmck-ThinkPad-P17-Gen-1> References: <20220418225345.GA3945110@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: Zqiang When booting kernels built with both CONFIG_RCU_STRICT_GRACE_PERIOD=y and CONFIG_PREEMPT_RT=y, the rcu_read_unlock_special() function's invocation of irq_work_queue_on() the init_irq_work() causes the rcu_preempt_deferred_qs_handler() function to work execute in SCHED_FIFO irq_work kthreads. Because rcu_read_unlock_special() is invoked on each rcu_read_unlock() in such kernels, the amount of work just keeps piling up, resulting in a boot-time hang. This commit therefore avoids this hang by using IRQ_WORK_INIT_HARD() instead of init_irq_work(), but only in kernels built with both CONFIG_PREEMPT_RT=y and CONFIG_RCU_STRICT_GRACE_PERIOD=y. Signed-off-by: Zqiang Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_plugin.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 5c23aceecd62..2a3715419073 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -661,7 +661,13 @@ static void rcu_read_unlock_special(struct task_struct *t) expboost && !rdp->defer_qs_iw_pending && cpu_online(rdp->cpu)) { // Get scheduler to re-evaluate and call hooks. // If !IRQ_WORK, FQS scan will eventually IPI. - init_irq_work(&rdp->defer_qs_iw, rcu_preempt_deferred_qs_handler); + if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) && + IS_ENABLED(CONFIG_PREEMPT_RT)) + rdp->defer_qs_iw = IRQ_WORK_INIT_HARD( + rcu_preempt_deferred_qs_handler); + else + init_irq_work(&rdp->defer_qs_iw, + rcu_preempt_deferred_qs_handler); rdp->defer_qs_iw_pending = true; irq_work_queue_on(&rdp->defer_qs_iw, rdp->cpu); } -- 2.31.1.189.g2e36527f23