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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 37D8EC35242 for ; Fri, 14 Feb 2020 23:56:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 05C3B206B6 for ; Fri, 14 Feb 2020 23:56:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581724584; bh=wSmco/Aj++Js7E9iUxiBfk6npGHQUrzPWCJ9ucxNPYk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=tyWRbVUjLzaw0Iz5s/9rH3+cxkOjljuF7Eo5a1kVQOxLVtMSfOLOCmma9SwA26hKZ fA6vJF7KQiZoyKFNFddhr77XdGKO83rqciHPN6f+CqUXjhrd7bmhDsv8czMax+QV/y 3ULGJFLO1DmgPxOWAP7ZIwrYwk4MgIL6CgMazWYU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728445AbgBNX4X (ORCPT ); Fri, 14 Feb 2020 18:56:23 -0500 Received: from mail.kernel.org ([198.145.29.99]:36112 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727649AbgBNX4V (ORCPT ); Fri, 14 Feb 2020 18:56:21 -0500 Received: from paulmck-ThinkPad-P72.c.hoisthospitality.com (unknown [62.84.152.189]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4B1C12081E; Fri, 14 Feb 2020 23:56:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581724581; bh=wSmco/Aj++Js7E9iUxiBfk6npGHQUrzPWCJ9ucxNPYk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=d5GrWpsIonBsJHDwWvFA/ze2sbSw4cyMnQ+jYm8U4/bf7W3zG2u44jiOUSLo3LMwo MmDwNWG5NUi1dFAPN5ze57TQqQoTQZmn1tbpvLDBBosBJGes2WTVUwbE7pP/0/L7p1 7zh6yfGrjKNP7upshDJP4jaCum1pSsbVD4UJ0/OE= From: paulmck@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 03/30] rcu: Fix exp_funnel_lock()/rcu_exp_wait_wake() datarace Date: Fri, 14 Feb 2020 15:55:40 -0800 Message-Id: <20200214235607.13749-3-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200214235536.GA13364@paulmck-ThinkPad-P72> References: <20200214235536.GA13364@paulmck-ThinkPad-P72> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" The rcu_node structure's ->exp_seq_rq field is accessed locklessly, so updates must use WRITE_ONCE(). This commit therefore adds the needed WRITE_ONCE() invocation where it was missed. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_exp.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index dcbd757..d7e0484 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -589,7 +589,7 @@ static void rcu_exp_wait_wake(unsigned long s) spin_lock(&rnp->exp_lock); /* Recheck, avoid hang in case someone just arrived. */ if (ULONG_CMP_LT(rnp->exp_seq_rq, s)) - rnp->exp_seq_rq = s; + WRITE_ONCE(rnp->exp_seq_rq, s); spin_unlock(&rnp->exp_lock); } smp_mb(); /* All above changes before wakeup. */ -- 2.9.5