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=-19.0 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 7D77FC4332D for ; Tue, 22 Dec 2020 01:38:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 53A1A22A83 for ; Tue, 22 Dec 2020 01:38:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726327AbgLVBif (ORCPT ); Mon, 21 Dec 2020 20:38:35 -0500 Received: from mail.kernel.org ([198.145.29.99]:51862 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725782AbgLVBie (ORCPT ); Mon, 21 Dec 2020 20:38:34 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id D2FDF22D2B; Tue, 22 Dec 2020 01:37:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1608601073; bh=J2A07UapJ9Zvfvi9rpOI6/cGmgTq6Q7dkbg2GukmBZ8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qf3dbitO+T00caFyyj+oNhxf/MdBORy5xOXVPl1t0hG55p0qTiCQ6K4mZg3SrAxT3 S2cnDRLWADxAyY9/6Q27QuzgcgqSahau4v0BZilUAlcvuQBVCaHQpviZC56Acym9N8 7A9mnAqgyvCF0KLquyvDwboej/LRYNlUovWREptyP08LolBzvFOTMaO0G1OwFKzWhF 64TQueiqO1WA/3e8fmXrr9H3EJ3d3PvXofDfuKXDqXI856EDTjowNewHY5kjpCVaFk /wXQd/rUnG2wznxqW7lI+tM8HXjbRi8v3l1E1Z3S4Xs8qy3bLd5TCGqQjtbtUnjYBS 0uJ6DmCH/Nfbw== From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , "Rafael J . Wysocki" , Peter Zijlstra , Ingo Molnar , Fabio Estevam , stable@vger.kernel.org, Thomas Gleixner , "Paul E . McKenney" , Len Brown , Pengutronix Kernel Team , NXP Linux Team , Daniel Lezcano , Shawn Guo , Sascha Hauer Subject: [PATCH 4/4] ACPI: processor: Fix missing need_resched() check after rcu_idle_enter() Date: Tue, 22 Dec 2020 02:37:12 +0100 Message-Id: <20201222013712.15056-5-frederic@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201222013712.15056-1-frederic@kernel.org> References: <20201222013712.15056-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Entering RCU idle mode may cause a deferred wake up of an RCU NOCB_GP kthread (rcuog) to be serviced. Usually a wake up happening while running the idle task is spotted in one of the need_resched() checks carefully placed within the idle loop that can break to the scheduler. Unfortunately within acpi_idle_enter_bm() the call to rcu_idle_enter() is already beyond the last generic need_resched() check. The cpu idle implementation happens to be ok because it ends up calling mwait_idle_with_hints() or acpi_safe_halt() which both perform their own need_resched() checks. But the suspend to idle implementation doesn't so it may suspend the CPU with a resched request unhandled, leaving the task hanging. Fix this with performing a last minute need_resched() check after calling rcu_idle_enter(). Reported-by: Paul E. McKenney Fixes: 1fecfdbb7acc (ACPI: processor: Take over RCU-idle for C3-BM idle) Cc: stable@vger.kernel.org Cc: Len Brown Cc: Peter Zijlstra Cc: Rafael J. Wysocki Cc: Thomas Gleixner Cc: Ingo Molnar Signed-off-by: Frederic Weisbecker --- drivers/acpi/processor_idle.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index d93e400940a3..c4939c49d972 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -604,8 +604,14 @@ static int acpi_idle_enter_bm(struct cpuidle_driver *drv, } rcu_idle_enter(); - - acpi_idle_do_entry(cx); + /* + * Last need_resched() check must come after rcu_idle_enter() + * which may wake up RCU internal tasks. mwait_idle_with_hints() + * and acpi_safe_halt() have their own checks but s2idle + * implementation doesn't. + */ + if (!need_resched()) + acpi_idle_do_entry(cx); rcu_idle_exit(); -- 2.25.1