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=-19.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 CDB69C4332D for ; Wed, 6 Jan 2021 16:49:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9AF272313A for ; Wed, 6 Jan 2021 16:49:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727724AbhAFQsw (ORCPT ); Wed, 6 Jan 2021 11:48:52 -0500 Received: from mail.kernel.org ([198.145.29.99]:54620 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727686AbhAFQsw (ORCPT ); Wed, 6 Jan 2021 11:48:52 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3025A23118; Wed, 6 Jan 2021 16:48:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1609951691; bh=heSMN5xcKRabpSBv4fJMPtXPF24uDi8PAuzbiJca4Zs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Z9G09+HetkNNUdeowdfN6KSll51PJbyIgIGbCd9Y1dg927Dzfya8y/2SBsL8LfTZD p6Dhwfm4EOZxOX1lKMEcGgcNL5Kucpwm+oJXpW9S5steRTf0tn/oPuxR0S/MUunS5H mfMombfSkoJZTX9BG8sAQRt4N/OVBloXAa4apEZyUJmpQ2bto/pQ8tAm+GTckWQMje w5VKXD4NJ1Z3xiMzQvpsaGJfJO2zxLBivTjTNQwF770NCJsZOrDUQfNPSV+wp3PA4S ROGmn8rpW0utTouw0i6gHqqXnD44p4YdrPXKxb+D0lraolLXGoiQc8QRRs/pnT290A pD7zW2OGgDwBA== From: paulmck@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, Sebastian Andrzej Siewior , "Paul E . McKenney" Subject: [PATCH tip/core/rcu 1/3] rcu: Make RCU_BOOST default on CONFIG_PREEMPT_RT Date: Wed, 6 Jan 2021 08:48:07 -0800 Message-Id: <20210106164809.20068-1-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20210106164746.GA19969@paulmck-ThinkPad-P72> References: <20210106164746.GA19969@paulmck-ThinkPad-P72> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Sebastian Andrzej Siewior On PREEMPT_RT kernels, RCU callbacks are deferred to the `rcuc' kthread. This can stall RCU grace periods due to lengthy preemption not only of RCU readers but also of 'rcuc' kthreads, either of which prevent grace periods from completing, which can in turn result in OOM. Because PREEMPT_RT kernels have more kthreads that can block grace periods, it is more important for such kernels to enable RCU_BOOST. This commit therefore makes RCU_BOOST the default on PREEMPT_RT. RCU_BOOST can still be manually disabled if need be. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Paul E. McKenney --- kernel/rcu/Kconfig | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig index cdc57b4..aa8cc8c9 100644 --- a/kernel/rcu/Kconfig +++ b/kernel/rcu/Kconfig @@ -188,8 +188,8 @@ config RCU_FAST_NO_HZ config RCU_BOOST bool "Enable RCU priority boosting" - depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT - default n + depends on (RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT) || PREEMPT_RT + default y if PREEMPT_RT help This option boosts the priority of preempted RCU readers that block the current preemptible RCU grace period for too long. -- 2.9.5