From nobody Sat Feb 7 21:24:18 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 9B2B3C001B0 for ; Sun, 2 Jul 2023 20:08:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231889AbjGBUIO (ORCPT ); Sun, 2 Jul 2023 16:08:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50476 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232952AbjGBUHi (ORCPT ); Sun, 2 Jul 2023 16:07:38 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B749B2698; Sun, 2 Jul 2023 13:05:45 -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 12ABF60C90; Sun, 2 Jul 2023 19:58:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 80BAEC433C8; Sun, 2 Jul 2023 19:58:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1688327892; bh=WfXYU0XTwimX7hvx+kdyEaHoUwk4tWIpYOn2FNmkAa4=; h=From:To:Cc:Subject:Date:From; b=guVdiqxIdC9Z6UOF2lgjDQ3p2smrq2W1ZwQmFc/TWeewZ+Y5c5JrEs/Dk8c3XIwXZ w3UCPReRGQatXLx2ru5bqbf0XCuuSylJ+k4tW64d+JdDquWvGaCbS6arfDYZJyI+4E uOOxAjb8g5Sgnd1PYMsrbR18WO/L76VhPy6I/V5G11fsK7wcoZa5uk2Nb/+cfotCoc nqDlQYDyEtgFW8WdjyNKqGiv8d5R57BpO1ZqVhuxu65KNOeIjQel54wxoOJfpL2StH TtvtH5FS4rf9Fwor1a6oByqD5YTsxX6RyzokjOJZMLFj8nRP57f7L506s4CAvoPwXC 8eYUzMaKuNChQ== 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 5.4] rcu: Mark rcu_cpu_kthread() accesses to ->rcu_cpu_has_work Date: Sun, 2 Jul 2023 15:58:09 -0400 Message-Id: <20230702195809.1793625-1-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 5.4.249 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 615283404d9dc..98d64f107fbb7 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2457,12 +2457,12 @@ 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