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 D7994C3B1BF for ; Sat, 15 Feb 2020 00:41:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A7C6C206CC for ; Sat, 15 Feb 2020 00:41:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581727310; bh=QDaV75XnBlFRQ31qZEJLn6dpbJkOPQueivDtsRfSAcg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ldJOfjy0ZBCdJdcdN791+UvTFUuCV/A+ZbzHC89+ys4/60ohd1YYSx7CsjFQN4gvC 1V1CqHQa8ddcbxfJkRkfyA2dCRKaa8yh3IP33m1Craal10CyFMP0KPjuFc/IPZLK1W 82sxPqT42J+GgMAtI6S8Ubre4bgJKiYFWJdBYva0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727944AbgBOAlu (ORCPT ); Fri, 14 Feb 2020 19:41:50 -0500 Received: from mail.kernel.org ([198.145.29.99]:48710 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725924AbgBOAlu (ORCPT ); Fri, 14 Feb 2020 19:41:50 -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 9F1E72081E; Sat, 15 Feb 2020 00:41:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581727309; bh=QDaV75XnBlFRQ31qZEJLn6dpbJkOPQueivDtsRfSAcg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NJgNXEvwZCcaI62QHVUmj//qq9YGXWvFUsmr0ySovHgoNFVS95ZDn3y8BRni8YoC9 74LdeAFgHxj/bPqFeiWW7bRGwjX+T/rgeOF9Uip1OzbFOD98v0fs4JxXFxzP5LQN7y UX0rhtsGIlAcd5qKwDstiLFx7gme6tMuJdDEaA0o= 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 12/18] rcutorture: Fix stray access to rcu_fwd_cb_nodelay Date: Fri, 14 Feb 2020 16:41:19 -0800 Message-Id: <20200215004125.16953-6-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: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: "Paul E. McKenney" The rcu_fwd_cb_nodelay variable suppresses excessively long read-side delays while carrying out an rcutorture forward-progress test. As such, it is accessed both by readers and updaters, and most of the accesses therefore use *_ONCE(). Except for one in rcu_read_delay(), which this commit fixes. This data race was reported by KCSAN. Not appropriate for backporting due to this being rcutorture. Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index edd9746..124160a 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -339,7 +339,7 @@ rcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp) * period, and we want a long delay occasionally to trigger * force_quiescent_state. */ - if (!rcu_fwd_cb_nodelay && + if (!READ_ONCE(rcu_fwd_cb_nodelay) && !(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) { started = cur_ops->get_gp_seq(); ts = rcu_trace_clock_local(); -- 2.9.5