From nobody Sat Feb 7 21:24:30 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B9266EB64D9 for ; Sun, 2 Jul 2023 20:04:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233093AbjGBUEB (ORCPT ); Sun, 2 Jul 2023 16:04:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49752 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233193AbjGBUC4 (ORCPT ); Sun, 2 Jul 2023 16:02:56 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2A4C65B8; Sun, 2 Jul 2023 12:59:38 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id F07D360CEC; Sun, 2 Jul 2023 19:58:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 744F0C433C7; Sun, 2 Jul 2023 19:58:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1688327889; bh=w2ivSFuV/xuPDlP6bFXHmhnvKcVqZc5rUq/vw0KQH4A=; h=From:To:Cc:Subject:Date:From; b=kytj1wREuO9TD5o6/ZdF7s8ZSoMr+EijftfpB0iF6BlS+cNgnutd3NVdrqlvw+Odw OLQAB94C0MPLQJoXeszhtgidjB7WrQbpK3bXOawHInKHE/LR6e1/zFweZ+EnG6yizX K71p1D7TK7V62SyWcnYIsEO+f7YyCTmCwHXrUb54wCu5MiHCltmGNpy0Ovy0TnjoJM 5HxsmbCFDueXRlewigufYMPVffoHlEf7XyO2/9mIeCeSUdz9GUBfgbqVY6ybNY0LNY YudSnLbatLBREz3J4f2bSVrJZLEdxC5KpQe+vQ2x7eP9aNVmB+6U3AnnjxxxJ+WMvp y+SjBftl4rdGQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Paul E. McKenney" , Sasha Levin , frederic@kernel.org, quic_neeraju@quicinc.com, joel@joelfernandes.org, josh@joshtriplett.org, boqun.feng@gmail.com, rcu@vger.kernel.org Subject: [PATCH AUTOSEL 5.10] rcu: Mark rcu_cpu_kthread() accesses to ->rcu_cpu_has_work Date: Sun, 2 Jul 2023 15:58:06 -0400 Message-Id: <20230702195806.1793552-1-sashal@kernel.org> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.10.186 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: "Paul E. McKenney" [ Upstream commit a24c1aab652ebacf9ea62470a166514174c96fe1 ] The rcu_data structure's ->rcu_cpu_has_work field can be modified by any CPU attempting to wake up the rcuc kthread. Therefore, this commit marks accesses to this field from the rcu_cpu_kthread() function. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney Signed-off-by: Sasha Levin --- kernel/rcu/tree.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index eec8e2f7537eb..b2c1ab260ed56 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2810,12 +2810,12 @@ static void rcu_cpu_kthread(unsigned int cpu) *statusp =3D RCU_KTHREAD_RUNNING; local_irq_disable(); work =3D *workp; - *workp =3D 0; + WRITE_ONCE(*workp, 0); local_irq_enable(); if (work) rcu_core(); local_bh_enable(); - if (*workp =3D=3D 0) { + if (!READ_ONCE(*workp)) { trace_rcu_utilization(TPS("End CPU kthread@rcu_wait")); *statusp =3D RCU_KTHREAD_WAITING; return; --=20 2.39.2