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=-20.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 E9F27C6377B for ; Wed, 21 Jul 2021 20:38:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CFD1060725 for ; Wed, 21 Jul 2021 20:38:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233171AbhGUT5z (ORCPT ); Wed, 21 Jul 2021 15:57:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:56328 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231740AbhGUT5p (ORCPT ); Wed, 21 Jul 2021 15:57:45 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8BAAB61221; Wed, 21 Jul 2021 20:38:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1626899901; bh=uo3mNzC8JGMN95RX/9rMuLZ2tfHn/qJe6eYq/zLbUPA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QTZrRS1GGtOB00DC2yzWdDK+eQAxiVMlCJRsHEuIPAeb5H4ol4TtXZqNJjCSL7iiq 0/aY7xiS6wImy4OH2J+nYYKjsDqDkBrlQeJgyWSPdrgXRHALJseWiFUousi+5ebcOQ h+xeN+ZBJ4zYAq1qjTLbhVzTg4Ng3m/POohUTwFmt1v/XExa8wkaYcoaOXQ5/Rdgbo zDDZdAKwVhk0672hCWH7qVO9VlwpD3oEq2WMbjVfNt1L6ic6Dkr+TNc4Rg25rEs7YX YqSfNmyQ1J0n3EsxS5F7WKs3eUYMYmekIvUqra8747LKIFisQyXJ3D+Qu6otPN1IVb S3OFmV6cXVXqQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 597595C0A11; Wed, 21 Jul 2021 13:38:21 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.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 rcu 3/5] rcu-tasks: Mark ->trc_reader_special.b.need_qs data races Date: Wed, 21 Jul 2021 13:38:16 -0700 Message-Id: <20210721203818.3398345-3-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20210721203758.GA3386731@paulmck-ThinkPad-P17-Gen-1> References: <20210721203758.GA3386731@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There are several ->trc_reader_special.b.need_qs data races that are too low-probability for KCSAN to notice, but which will happen sooner or later. This commit therefore marks these accesses. Signed-off-by: Paul E. McKenney --- kernel/rcu/tasks.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index f6b5320c44849..1cece5e9be9a9 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -850,7 +850,7 @@ static DEFINE_IRQ_WORK(rcu_tasks_trace_iw, rcu_read_unlock_iw); /* If we are the last reader, wake up the grace-period kthread. */ void rcu_read_unlock_trace_special(struct task_struct *t, int nesting) { - int nq = t->trc_reader_special.b.need_qs; + int nq = READ_ONCE(t->trc_reader_special.b.need_qs); if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) && t->trc_reader_special.b.need_mb) @@ -916,7 +916,7 @@ static void trc_read_check_handler(void *t_in) // Get here if the task is in a read-side critical section. Set // its state so that it will awaken the grace-period kthread upon // exit from that critical section. - WARN_ON_ONCE(t->trc_reader_special.b.need_qs); + WARN_ON_ONCE(READ_ONCE(t->trc_reader_special.b.need_qs)); WRITE_ONCE(t->trc_reader_special.b.need_qs, true); reset_ipi: @@ -968,7 +968,7 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg) // state so that it will awaken the grace-period kthread upon exit // from that critical section. atomic_inc(&trc_n_readers_need_end); // One more to wait on. - WARN_ON_ONCE(t->trc_reader_special.b.need_qs); + WARN_ON_ONCE(READ_ONCE(t->trc_reader_special.b.need_qs)); WRITE_ONCE(t->trc_reader_special.b.need_qs, true); return true; } @@ -1103,7 +1103,7 @@ static void show_stalled_task_trace(struct task_struct *t, bool *firstreport) ".i"[is_idle_task(t)], ".N"[cpu > 0 && tick_nohz_full_cpu(cpu)], READ_ONCE(t->trc_reader_nesting), - " N"[!!t->trc_reader_special.b.need_qs], + " N"[!!READ_ONCE(t->trc_reader_special.b.need_qs)], cpu); sched_show_task(t); } -- 2.31.1.189.g2e36527f23