From patchwork Mon Jan 4 15:20:58 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frederic Weisbecker X-Patchwork-Id: 356782 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=-19.2 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=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 DF892C433E9 for ; Mon, 4 Jan 2021 15:22:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B58102242A for ; Mon, 4 Jan 2021 15:22:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727458AbhADPWA (ORCPT ); Mon, 4 Jan 2021 10:22:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:54976 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727403AbhADPV7 (ORCPT ); Mon, 4 Jan 2021 10:21:59 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 12A9722286; Mon, 4 Jan 2021 15:21:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1609773679; bh=KnCcCfl5Ujo0xeLkI0m9dHw2QY6hrFRxzWMXtqAvrxY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bls+adfd/7XPttxskOXdd0DZvtCeb+LUIOhIrUhnEaaQmJZthY+QbmtdxKkRyJb+I fyHgXJHGiLnaZUPKkncqdC+DMIKr/jmP8HGkD3HF2wIXB/mo5GODrv2rQYXNe5uV8U BWsoQIyWNpF+zAhdDTz/OGLrSTmEwEG0azq+cNxd8aR4nQ1bhnobwYe51Z+6dIe9bm CZsE1zUXnV7YNIq6PlYZuvRKJfHTUUtKACb8XzOh1bcOi8kIo+ldGmCAd42fEscmhq PPrlWy/RTstaGbPRHfRLI3oIp+JL2GvrEneCuzUsFGmnYzF+QpkU5KPoXydmXTHKdR KzBWkGcjahvsw== From: Frederic Weisbecker To: Peter Zijlstra Cc: LKML , Frederic Weisbecker , "Rafael J . Wysocki" , 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: Mon, 4 Jan 2021 16:20:58 +0100 Message-Id: <20210104152058.36642-5-frederic@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210104152058.36642-1-frederic@kernel.org> References: <20210104152058.36642-1-frederic@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@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 Reviewed-by: Rafael J. Wysocki Fixes: 1fecfdbb7acc (ACPI: processor: Take over RCU-idle for C3-BM idle) Cc: stable@vger.kernel.org Cc: Len Brown Cc: Peter Zijlstra 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();