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=-20.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=unavailable 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 7778DC433DB for ; Wed, 10 Feb 2021 13:54:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2BD0864E6F for ; Wed, 10 Feb 2021 13:54:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231666AbhBJNyf (ORCPT ); Wed, 10 Feb 2021 08:54:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33914 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231425AbhBJNyQ (ORCPT ); Wed, 10 Feb 2021 08:54:16 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 85570C061756; Wed, 10 Feb 2021 05:53:34 -0800 (PST) Date: Wed, 10 Feb 2021 13:53:32 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1612965213; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=lqc+HTf6+ILxbzPBPQ/wQPJd7fxr8L9cQOc3J/vkmk8=; b=lhtP2T1QNwb2655jmt8OlDnJynCWXJVpCim8RdBzNbKcBSZLiim2g9ppufy71xT/4QiHbU 994h/dGbx/h1qg5zQV+Mt4uWdvLhx30t06Uph7f4TNmlzabFFdSqAc/TozuBvMJdX0CgaO /DiLbi3NItYn05ypqc/FVtzOdNpbqurfYuC86J1wlf1pzXcM9zFuvS08/aI9SegbdsWIeS MBuuhB5x/hUhDFuxUOqApGgjJridjNrlPcBIhz7xchedMGJnBxQtcXSgbJ3yl/S7SxpJJ+ YUK0AOsKGCjKr2ncCc/3sRoR0IrIi4adSSznqeaGBruHkbNeerkDYP3FmmzguA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1612965213; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=lqc+HTf6+ILxbzPBPQ/wQPJd7fxr8L9cQOc3J/vkmk8=; b=5RHmH5mpJ+vSMRC4XZMLpgMWrTp1UR7tWkBMvSRSOG+HPo2zfrEHJ5WchigdIE5w6RLUC/ r96NkCGJBbO/FqBw== From: "tip-bot2 for Frederic Weisbecker" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] rcu/nocb: Perform deferred wake up before last idle's need_resched() check Cc: "Paul E. McKenney" , Frederic Weisbecker , "Peter Zijlstra (Intel)" , stable@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210131230548.32970-3-frederic@kernel.org> References: <20210131230548.32970-3-frederic@kernel.org> MIME-Version: 1.0 Message-ID: <161296521258.23325.15350717155296701508.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 3a7b5c87a0b29c8554a9bdbbbd75eeb4176fb5d4 Gitweb: https://git.kernel.org/tip/3a7b5c87a0b29c8554a9bdbbbd75eeb4176fb5d4 Author: Frederic Weisbecker AuthorDate: Mon, 01 Feb 2021 00:05:45 +01:00 Committer: Peter Zijlstra CommitterDate: Wed, 10 Feb 2021 14:44:50 +01:00 rcu/nocb: Perform deferred wake up before last idle's need_resched() check Entering RCU idle mode may cause a deferred wake up of an RCU NOCB_GP kthread (rcuog) to be serviced. Usually a local wake up happening while running the idle task is handled in one of the need_resched() checks carefully placed within the idle loop that can break to the scheduler. Unfortunately the call to rcu_idle_enter() is already beyond the last generic need_resched() check and we may halt the CPU with a resched request unhandled, leaving the task hanging. Fix this with splitting the rcuog wakeup handling from rcu_idle_enter() and place it before the last generic need_resched() check in the idle loop. It is then assumed that no call to call_rcu() will be performed after that in the idle loop until the CPU is put in low power mode. Fixes: 96d3fd0d315a (rcu: Break call_rcu() deadlock involving scheduler and perf) Reported-by: Paul E. McKenney Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20210131230548.32970-3-frederic@kernel.org --- include/linux/rcupdate.h | 2 ++ kernel/rcu/tree.c | 3 --- kernel/rcu/tree_plugin.h | 5 +++++ kernel/sched/idle.c | 1 + 4 files changed, 8 insertions(+), 3 deletions(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index fd02c5f..36c2119 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -110,8 +110,10 @@ static inline void rcu_user_exit(void) { } #ifdef CONFIG_RCU_NOCB_CPU void rcu_init_nohz(void); +void rcu_nocb_flush_deferred_wakeup(void); #else /* #ifdef CONFIG_RCU_NOCB_CPU */ static inline void rcu_init_nohz(void) { } +static inline void rcu_nocb_flush_deferred_wakeup(void) { } #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ /** diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 63032e5..82838e9 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -671,10 +671,7 @@ static noinstr void rcu_eqs_enter(bool user) */ void rcu_idle_enter(void) { - struct rcu_data *rdp = this_cpu_ptr(&rcu_data); - lockdep_assert_irqs_disabled(); - do_nocb_deferred_wakeup(rdp); rcu_eqs_enter(false); } EXPORT_SYMBOL_GPL(rcu_idle_enter); diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 7e291ce..d5b38c2 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2187,6 +2187,11 @@ static void do_nocb_deferred_wakeup(struct rcu_data *rdp) do_nocb_deferred_wakeup_common(rdp); } +void rcu_nocb_flush_deferred_wakeup(void) +{ + do_nocb_deferred_wakeup(this_cpu_ptr(&rcu_data)); +} + void __init rcu_init_nohz(void) { int cpu; diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 305727e..7199e6f 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -285,6 +285,7 @@ static void do_idle(void) } arch_cpu_idle_enter(); + rcu_nocb_flush_deferred_wakeup(); /* * In poll mode we reenable interrupts and spin. Also if we