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 4E1B4C433E6 for ; Mon, 1 Mar 2021 11:30:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 23C696146B for ; Mon, 1 Mar 2021 11:30:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233694AbhCAL37 (ORCPT ); Mon, 1 Mar 2021 06:29:59 -0500 Received: from forward1-smtp.messagingengine.com ([66.111.4.223]:49767 "EHLO forward1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233662AbhCAL3u (ORCPT ); Mon, 1 Mar 2021 06:29:50 -0500 Received: from compute4.internal (compute4.nyi.internal [10.202.2.44]) by mailforward.nyi.internal (Postfix) with ESMTP id C7C12194142B; Mon, 1 Mar 2021 06:28:25 -0500 (EST) Received: from mailfrontend1 ([10.202.2.162]) by compute4.internal (MEProxy); Mon, 01 Mar 2021 06:28:25 -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=vCbzMS Ak/jmm4MVThtdtYgjbX5GqNTUXGsTzlS+cZZE=; b=QFNkz5NZR7JsylP4WNmjN/ fOe9DRQeDBm1RrpJePU9A5Pji4hNOA+sLKpwDk1yGggAN/syCOtdxX9JQSKmeLII hpE9r/N9SkyCHI+h4oqlZ9IupwIh942UcIXbEdcTNyS6TRtdW5+iBRP/mNHBdHs0 Csomg9yN5t/dhyoW75qhdAyGnpBKrwM0inZMK/NWGsRICGcR+0QxIDoTXQtTaqpP Atm0fH2aMZA4jit28vIsyK0p4TXeMI2Zr8KkO8Tse9fjsRzsnyigoRAX9cxy452D VM96REOiNxziCwEQo3DSng2FNzAIZj0nIo+rMK0eLryt2t7jW5IFuDI3cUZFjwZw == X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeduledrleekgddvjecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecunecujfgurhepuffvhfffkfggtgfgsehtkeertddttd flnecuhfhrohhmpeeoghhrvghgkhhhsehlihhnuhigfhhouhhnuggrthhiohhnrdhorhhg qeenucggtffrrghtthgvrhhnpeelleelvdegfeelledtteegudegfffghfduffduudekge efleegieegkeejhfelveenucffohhmrghinhepkhgvrhhnvghlrdhorhhgnecukfhppeek fedrkeeirdejgedrieegnecuvehluhhsthgvrhfuihiivgepjeenucfrrghrrghmpehmrg 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 727FB24005A; Mon, 1 Mar 2021 06:28:25 -0500 (EST) Subject: FAILED: patch "[PATCH] rcu/nocb: Trigger self-IPI on late deferred wake up before" failed to apply to 4.14-stable tree To: frederic@kernel.org, mingo@kernel.org, paulmck@kernel.org, peterz@infradead.org Cc: From: Date: Mon, 01 Mar 2021 12:28:22 +0100 Message-ID: <1614598102100226@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 4.14-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 f8bb5cae9616224a39cbb399de382d36ac41df10 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 1 Feb 2021 00:05:46 +0100 Subject: [PATCH] rcu/nocb: Trigger self-IPI on late deferred wake up before user resume Entering RCU idle mode may cause a deferred wake up of an RCU NOCB_GP kthread (rcuog) to be serviced. Unfortunately the call to rcu_user_enter() is already past the last rescheduling opportunity before we resume to userspace or to guest mode. We may escape there with the woken task ignored. The ultimate resort to fix every callsites is to trigger a self-IPI (nohz_full depends on arch to implement arch_irq_work_raise()) that will trigger a reschedule on IRQ tail or guest exit. Eventually every site that want a saner treatment will need to carefully place a call to rcu_nocb_flush_deferred_wakeup() before the last explicit need_resched() check upon resume. 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/20210131230548.32970-4-frederic@kernel.org diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 82838e93b498..4b1e5bd16492 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -677,6 +677,18 @@ void rcu_idle_enter(void) EXPORT_SYMBOL_GPL(rcu_idle_enter); #ifdef CONFIG_NO_HZ_FULL + +/* + * An empty function that will trigger a reschedule on + * IRQ tail once IRQs get re-enabled on userspace resume. + */ +static void late_wakeup_func(struct irq_work *work) +{ +} + +static DEFINE_PER_CPU(struct irq_work, late_wakeup_work) = + IRQ_WORK_INIT(late_wakeup_func); + /** * rcu_user_enter - inform RCU that we are resuming userspace. * @@ -694,12 +706,19 @@ noinstr void rcu_user_enter(void) lockdep_assert_irqs_disabled(); + /* + * We may be past the last rescheduling opportunity in the entry code. + * Trigger a self IPI that will fire and reschedule once we resume to + * user/guest mode. + */ instrumentation_begin(); - do_nocb_deferred_wakeup(rdp); + if (do_nocb_deferred_wakeup(rdp) && need_resched()) + irq_work_queue(this_cpu_ptr(&late_wakeup_work)); instrumentation_end(); rcu_eqs_enter(true); } + #endif /* CONFIG_NO_HZ_FULL */ /** diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 7708ed161f4a..9226f4021a36 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -433,7 +433,7 @@ static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp, static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty, unsigned long flags); static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp); -static void do_nocb_deferred_wakeup(struct rcu_data *rdp); +static bool do_nocb_deferred_wakeup(struct rcu_data *rdp); static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); static void rcu_spawn_cpu_nocb_kthread(int cpu); static void __init rcu_spawn_nocb_kthreads(void); diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index d5b38c28abd1..384856e4d13e 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1631,8 +1631,8 @@ bool rcu_is_nocb_cpu(int cpu) * Kick the GP kthread for this NOCB group. Caller holds ->nocb_lock * and this function releases it. */ -static void wake_nocb_gp(struct rcu_data *rdp, bool force, - unsigned long flags) +static bool wake_nocb_gp(struct rcu_data *rdp, bool force, + unsigned long flags) __releases(rdp->nocb_lock) { bool needwake = false; @@ -1643,7 +1643,7 @@ static void wake_nocb_gp(struct rcu_data *rdp, bool force, trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("AlreadyAwake")); rcu_nocb_unlock_irqrestore(rdp, flags); - return; + return false; } del_timer(&rdp->nocb_timer); rcu_nocb_unlock_irqrestore(rdp, flags); @@ -1656,6 +1656,8 @@ static void wake_nocb_gp(struct rcu_data *rdp, bool force, raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags); if (needwake) wake_up_process(rdp_gp->nocb_gp_kthread); + + return needwake; } /* @@ -2152,20 +2154,23 @@ static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) } /* Do a deferred wakeup of rcu_nocb_kthread(). */ -static void do_nocb_deferred_wakeup_common(struct rcu_data *rdp) +static bool do_nocb_deferred_wakeup_common(struct rcu_data *rdp) { unsigned long flags; int ndw; + int ret; rcu_nocb_lock_irqsave(rdp, flags); if (!rcu_nocb_need_deferred_wakeup(rdp)) { rcu_nocb_unlock_irqrestore(rdp, flags); - return; + return false; } ndw = READ_ONCE(rdp->nocb_defer_wakeup); WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT); - wake_nocb_gp(rdp, ndw == RCU_NOCB_WAKE_FORCE, flags); + ret = wake_nocb_gp(rdp, ndw == RCU_NOCB_WAKE_FORCE, flags); trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DeferredWake")); + + return ret; } /* Do a deferred wakeup of rcu_nocb_kthread() from a timer handler. */ @@ -2181,10 +2186,11 @@ static void do_nocb_deferred_wakeup_timer(struct timer_list *t) * This means we do an inexact common-case check. Note that if * we miss, ->nocb_timer will eventually clean things up. */ -static void do_nocb_deferred_wakeup(struct rcu_data *rdp) +static bool do_nocb_deferred_wakeup(struct rcu_data *rdp) { if (rcu_nocb_need_deferred_wakeup(rdp)) - do_nocb_deferred_wakeup_common(rdp); + return do_nocb_deferred_wakeup_common(rdp); + return false; } void rcu_nocb_flush_deferred_wakeup(void) @@ -2523,8 +2529,9 @@ static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) return false; } -static void do_nocb_deferred_wakeup(struct rcu_data *rdp) +static bool do_nocb_deferred_wakeup(struct rcu_data *rdp) { + return false; } static void rcu_spawn_cpu_nocb_kthread(int cpu)