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=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 31149C35242 for ; Fri, 14 Feb 2020 23:56:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0164724673 for ; Fri, 14 Feb 2020 23:56:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581724612; bh=LusdN1UJW4wsth9V10brAmgIfZk/VRwPHX4oDZzSg/U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=rHfa6mYslDsKjzZIKSxJxIizdImILBEvvM4guGsXbziJ6VORb6ShWkwmTyey27ewi nu0JYDBO2CUpxkgCTvso/LHVgkQrwLMuBj9U8Og/wv6blIBGwfIpMo5dHdTkrQgoGb jcSMOmPDTGJp5kyHe5mWzDeJsG9Bwdf90+U0+LZo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727951AbgBNX4v (ORCPT ); Fri, 14 Feb 2020 18:56:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:36664 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726164AbgBNX4v (ORCPT ); Fri, 14 Feb 2020 18:56:51 -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 5F4D42072D; Fri, 14 Feb 2020 23:56:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581724610; bh=LusdN1UJW4wsth9V10brAmgIfZk/VRwPHX4oDZzSg/U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Zxxr6D+tkx+QBe+lX88UvrN1ZcLw6/43u5z0npTTc/54Cw5jpYbzuRYVwiajmcM88 K1zAth7UJvzuolk1kDKTTXzBvt2sCds5/RlQN5xJMhh/wXEZ9nBm2f3OxMqqJ8CCJE oWQX+yOb/NSM59oQ2tpLXusdE9WajZRTpFLrNPdI= 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 11/30] rcu: Add READ_ONCE() to rcu_segcblist ->tails[] Date: Fri, 14 Feb 2020 15:55:48 -0800 Message-Id: <20200214235607.13749-11-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: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: "Paul E. McKenney" The rcu_segcblist structure's ->tails[] array entries are read locklessly, so this commit adds the READ_ONCE() to a load in order to avoid destructive compiler optimizations. This data race was reported by KCSAN. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcu_segcblist.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c index 5f4fd3b..426a472 100644 --- a/kernel/rcu/rcu_segcblist.c +++ b/kernel/rcu/rcu_segcblist.c @@ -182,7 +182,7 @@ void rcu_segcblist_offload(struct rcu_segcblist *rsclp) bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp) { return rcu_segcblist_is_enabled(rsclp) && - &rsclp->head != rsclp->tails[RCU_DONE_TAIL]; + &rsclp->head != READ_ONCE(rsclp->tails[RCU_DONE_TAIL]); } /* -- 2.9.5