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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 21C7FC433E0 for ; Mon, 1 Mar 2021 11:29:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D4B1464DF5 for ; Mon, 1 Mar 2021 11:29:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232654AbhCAL3D (ORCPT ); Mon, 1 Mar 2021 06:29:03 -0500 Received: from forward1-smtp.messagingengine.com ([66.111.4.223]:32829 "EHLO forward1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232199AbhCAL3B (ORCPT ); Mon, 1 Mar 2021 06:29:01 -0500 Received: from compute4.internal (compute4.nyi.internal [10.202.2.44]) by mailforward.nyi.internal (Postfix) with ESMTP id C371D19413C4; Mon, 1 Mar 2021 06:27:54 -0500 (EST) Received: from mailfrontend1 ([10.202.2.162]) by compute4.internal (MEProxy); Mon, 01 Mar 2021 06:27:54 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:message-id:mime-version:subject:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm2; bh=D43yBE rS0EhmPpU6YFrqmpvedRordcoLc7q+efF+3lY=; b=H20gyyKWgo6XMcP0AlAeT3 TzEi1iyqNNIQa1c8Fzk9ea++DbAIusY1PVQ8MhalYN4PZau97hbonTvYMUdsFJs5 tRMz9kCVePUAGhA0M9ooM5kvaGaKasMYmIJDCinD0fPTg26uCZPT9Hs/NMtsHb32 EN99ZOXFufv6UQD3myDSIZemapoP5N74o+5vMEf5Mczx2hIuOY3/ECiqKJ9QZwcb MSGCph0qIx3SrJ5pyKAMPHxkHo8Kkg6/hNgBDMAGzLJnHPjw8luwJICB21W7rU8F 7CXfURbPdkL1MeGt9qO9X5DcmESFS2LLIcPbGobKzqjxz0xxnUNhKahXMlQydvtA == X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeduledrleekgddvjecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecunecujfgurhepuffvhfffkfggtgfgsehtkeertddttd flnecuhfhrohhmpeeoghhrvghgkhhhsehlihhnuhigfhhouhhnuggrthhiohhnrdhorhhg qeenucggtffrrghtthgvrhhnpeelleelvdegfeelledtteegudegfffghfduffduudekge efleegieegkeejhfelveenucffohhmrghinhepkhgvrhhnvghlrdhorhhgnecukfhppeek fedrkeeirdejgedrieegnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrg hilhhfrhhomhepghhrvghgsehkrhhorghhrdgtohhm X-ME-Proxy: Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) by mail.messagingengine.com (Postfix) with ESMTPA id 0DB03240065; Mon, 1 Mar 2021 06:27:53 -0500 (EST) Subject: FAILED: patch "[PATCH] rcu/nocb: Perform deferred wake up before last idle's" failed to apply to 4.9-stable tree To: frederic@kernel.org, mingo@kernel.org, paulmck@kernel.org, peterz@infradead.org Cc: From: Date: Mon, 01 Mar 2021 12:27:50 +0100 Message-ID: <1614598070159165@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 43789ef3f7d61aa7bed0cb2764e588fc990c30ef Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 1 Feb 2021 00:05:45 +0100 Subject: [PATCH] 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) Signed-off-by: Ingo Molnar Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20210131230548.32970-3-frederic@kernel.org diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index fd02c5fa60cb..36c2119de702 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 63032e5620b9..82838e93b498 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 7e291ce0a1d6..d5b38c28abd1 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 305727ea0677..7199e6f23789 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