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 A29F9C35242 for ; Sat, 15 Feb 2020 00:41:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7C753206CC for ; Sat, 15 Feb 2020 00:41:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581727309; bh=UaNRIzw8PdKi+H1pVKj+hGEjageya5/rTyvnZCayyqs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=NBeZyD671iK9dMs776IpRH+uiS2KxdrJbfnLjEC5MvqNdl8fa+T73M+nYwVAD1ziq 5H6QC2CSspj5CYufgM7bzyvbjk/FNL+D4sxfF31bvmLtj6YE3tnGIi+uU8N9O+q7VJ +yaKm07uS+R0wClHGWdhBgiyH7zrvGIp5fcUPOjY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727943AbgBOAls (ORCPT ); Fri, 14 Feb 2020 19:41:48 -0500 Received: from mail.kernel.org ([198.145.29.99]:48644 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725924AbgBOAlq (ORCPT ); Fri, 14 Feb 2020 19:41:46 -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 C82B322314; Sat, 15 Feb 2020 00:41:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581727306; bh=UaNRIzw8PdKi+H1pVKj+hGEjageya5/rTyvnZCayyqs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Bm067/TUzBOiKDLeWS5/Je0OAv27Tw/uB9I0UtT9t7gIhsNXu//ryAK1AwyKupUNd kxgI82uHPlFHQsnPNPEUUoKviYlBrx0VxvYtshWVUd4jbf1AqFyqILd4c0KoayQz1r CfRTCuEoicLz3eQt4jiEPzWChRPCYf7quvdKuE4Y= 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 11/18] rcutorture: Fix rcu_torture_one_read()/rcu_torture_writer() data race Date: Fri, 14 Feb 2020 16:41:18 -0800 Message-Id: <20200215004125.16953-5-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200215003634.GA16227@paulmck-ThinkPad-P72> References: <20200215003634.GA16227@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 ->rtort_pipe_count field in the rcu_torture structure checks for too-short grace periods, and is therefore read by rcutorture's readers while being updated by rcutorture's writers. This commit therefore adds the needed READ_ONCE() and WRITE_ONCE() invocations. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely and due to this being rcutorture. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 5efd950..edd9746 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -375,11 +375,12 @@ rcu_torture_pipe_update_one(struct rcu_torture *rp) { int i; - i = rp->rtort_pipe_count; + i = READ_ONCE(rp->rtort_pipe_count); if (i > RCU_TORTURE_PIPE_LEN) i = RCU_TORTURE_PIPE_LEN; atomic_inc(&rcu_torture_wcount[i]); - if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) { + WRITE_ONCE(rp->rtort_pipe_count, i + 1); + if (rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) { rp->rtort_mbtest = 0; return true; } @@ -1015,7 +1016,8 @@ rcu_torture_writer(void *arg) if (i > RCU_TORTURE_PIPE_LEN) i = RCU_TORTURE_PIPE_LEN; atomic_inc(&rcu_torture_wcount[i]); - old_rp->rtort_pipe_count++; + WRITE_ONCE(old_rp->rtort_pipe_count, + old_rp->rtort_pipe_count + 1); switch (synctype[torture_random(&rand) % nsynctypes]) { case RTWS_DEF_FREE: rcu_torture_writer_state = RTWS_DEF_FREE; @@ -1291,7 +1293,7 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp) atomic_inc(&n_rcu_torture_mberror); rtrsp = rcutorture_loop_extend(&readstate, trsp, rtrsp); preempt_disable(); - pipe_count = p->rtort_pipe_count; + pipe_count = READ_ONCE(p->rtort_pipe_count); if (pipe_count > RCU_TORTURE_PIPE_LEN) { /* Should not happen, but... */ pipe_count = RCU_TORTURE_PIPE_LEN; -- 2.9.5