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 DBAC5C35242 for ; Sat, 15 Feb 2020 00:29:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B3F51207FF for ; Sat, 15 Feb 2020 00:29:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581726580; bh=EJexEEpX+GQ8fYQ/Mz/rgmbw0ukwN9BOCgXLakmHZOI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Zb+RnEmvlRSn0Elm41SB/YngCLc85FDrKmmrNJ/kR5eJUJZYEm3kQWAOZmwLSuN1h Kzed43JhyldJU0UC/USmhBwfco3SNvQBWkQh+GFPZKz4b/fEIMV14KnKAzFrNHoW2O QlR5T4L2RD1/FnmU83AYSubX36tcGYZ8tIosqUvY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727567AbgBOA3k (ORCPT ); Fri, 14 Feb 2020 19:29:40 -0500 Received: from mail.kernel.org ([198.145.29.99]:45240 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727529AbgBOA3k (ORCPT ); Fri, 14 Feb 2020 19:29:40 -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 A707F206D7; Sat, 15 Feb 2020 00:29:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581726579; bh=EJexEEpX+GQ8fYQ/Mz/rgmbw0ukwN9BOCgXLakmHZOI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mgHIuvl0TVeJ66h6B8sC5QGWe4hy1JFmcByEx7BUKTJjk+71nbZFLzhZqnPbNQe+Y IjsY1cfYNnaZSOtSXFJhSxAYgpTeS4aj3+AZ4FNaphueOjbCfdmgGBYQA3xZZaJ5QE auNZmYqUwU+RmBX/o55LI5cBz+EQyjJP/6sJV6WQ= 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 1/4] srcu: Fix __call_srcu()/process_srcu() datarace Date: Fri, 14 Feb 2020 16:29:29 -0800 Message-Id: <20200215002932.15976-1-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: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: "Paul E. McKenney" The srcu_node structure's ->srcu_gp_seq_needed_exp field is accessed locklessly, so updates must use WRITE_ONCE(). This commit therefore adds the needed WRITE_ONCE() invocations. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney --- kernel/rcu/srcutree.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 657e6a7..b1edac9 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -550,7 +550,7 @@ static void srcu_gp_end(struct srcu_struct *ssp) snp->srcu_have_cbs[idx] = gpseq; rcu_seq_set_state(&snp->srcu_have_cbs[idx], 1); if (ULONG_CMP_LT(snp->srcu_gp_seq_needed_exp, gpseq)) - snp->srcu_gp_seq_needed_exp = gpseq; + WRITE_ONCE(snp->srcu_gp_seq_needed_exp, gpseq); mask = snp->srcu_data_have_cbs[idx]; snp->srcu_data_have_cbs[idx] = 0; spin_unlock_irq_rcu_node(snp); @@ -660,7 +660,7 @@ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp, if (snp == sdp->mynode) snp->srcu_data_have_cbs[idx] |= sdp->grpmask; if (!do_norm && ULONG_CMP_LT(snp->srcu_gp_seq_needed_exp, s)) - snp->srcu_gp_seq_needed_exp = s; + WRITE_ONCE(snp->srcu_gp_seq_needed_exp, s); spin_unlock_irqrestore_rcu_node(snp, flags); } -- 2.9.5