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 C390AC35242 for ; Sat, 15 Feb 2020 00:29:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 931EF2083B for ; Sat, 15 Feb 2020 00:29:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581726592; bh=XdMJOms8RbFN2DS7z+iHuxwTOky+fnSYiXiwhbUyJSI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=dOqMKHFDp1cVr8piLuD+5k/dLtpSWwrsGadAVMS0mId3LdIU8vqNZxbfOWBYKFFoC MX9DZlirlqfoZ7y9vAjccNz8mAFNzh+Wn2crMrgckyfG1umaWx3FkjqJrLaU0u1MRR rdFao8vnhErrLihG9oUaxGAo13meDoGCkYQ6jeJ8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727918AbgBOA3w (ORCPT ); Fri, 14 Feb 2020 19:29:52 -0500 Received: from mail.kernel.org ([198.145.29.99]:45546 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727567AbgBOA3v (ORCPT ); Fri, 14 Feb 2020 19:29:51 -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 65FBD207FF; Sat, 15 Feb 2020 00:29:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581726590; bh=XdMJOms8RbFN2DS7z+iHuxwTOky+fnSYiXiwhbUyJSI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cBc9XNaWmAo84NIbK+z57M9ndzCt02Wr0Tq8K5wUjl1p0dCbCSvp5PPa/7vja6j5b LA5gIhZnfuijWpaXS1RfjkBZ2DAmfJ5lSZE51/3orm15eh++gR4Vbo8KHhk4ltgjn0 YhfbGVG5X+T28xIjTXMOaZet9iq5nquRbvrMI8JU= 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 4/4] srcu: Add READ_ONCE() to srcu_struct ->srcu_gp_seq load Date: Fri, 14 Feb 2020 16:29:32 -0800 Message-Id: <20200215002932.15976-4-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200215002907.GA15895@paulmck-ThinkPad-P72> References: <20200215002907.GA15895@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 load of the srcu_struct structure's ->srcu_gp_seq field in srcu_funnel_gp_start() is lockless, so this commit adds the requisite READ_ONCE(). This data race was reported by KCSAN. Signed-off-by: Paul E. McKenney --- kernel/rcu/srcutree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 119a373..90ab475 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -678,7 +678,7 @@ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp, /* If grace period not already done and none in progress, start it. */ if (!rcu_seq_done(&ssp->srcu_gp_seq, s) && - rcu_seq_state(ssp->srcu_gp_seq) == SRCU_STATE_IDLE) { + rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) == SRCU_STATE_IDLE) { WARN_ON_ONCE(ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed)); srcu_gp_start(ssp); if (likely(srcu_init_done)) -- 2.9.5