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 87E44C3815B for ; Wed, 15 Apr 2020 17:11:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3C4A721744 for ; Wed, 15 Apr 2020 17:11:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586970669; bh=dmpyRpRc++xi9KkXweAWSawKqD80BTw54kiQlk5yZVo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ODv1f8YSviU0i16AAqdcWIO/qpAc95ZvDMcp0fEIIlVpxziKl+uQhYTsEjnG65qgz WScBi2hO8Erl5WNw5PYE2ELQBtxS+zHqUp+Tp187klm/FdHHYaohAyOk4I97kvCKIx NqgbQj8WjfULyt4ZakAd5+OqBsZnQaxL9kh31ftE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2410742AbgDORLG (ORCPT ); Wed, 15 Apr 2020 13:11:06 -0400 Received: from mail.kernel.org ([198.145.29.99]:42212 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2410710AbgDORK5 (ORCPT ); Wed, 15 Apr 2020 13:10:57 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (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 D81E421973; Wed, 15 Apr 2020 17:10:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1586970657; bh=dmpyRpRc++xi9KkXweAWSawKqD80BTw54kiQlk5yZVo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1tVbQd/dvCVWYC2kNLKlHCDMVJDHASlNKsYSe1LPvlE1fLHuLR0TZP2xDHDou00cO 2ueBIzta+BYucxSRFfpf+AJshmQoAbAkE2KoPas79HThfUhm+s5WEx1K42xAZ8QKlX KMcF3nYI1l3wGAh4b5AlSBo1miDKqVfZTBYWAmj4= 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 03/19] rcu: Mark rcu_state.ncpus to detect concurrent writes Date: Wed, 15 Apr 2020 10:10:38 -0700 Message-Id: <20200415171054.9013-3-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200415171017.GA7821@paulmck-ThinkPad-P72> References: <20200415171017.GA7821@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 rcu_state structure's ncpus field is only to be modified by the CPU-hotplug CPU-online code path, which is single-threaded. This commit therefore enlists KCSAN's help in enforcing this restriction. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index f13130a..4fd3e0f 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3612,6 +3612,7 @@ void rcu_cpu_starting(unsigned int cpu) nbits = bitmap_weight(&oldmask, BITS_PER_LONG); /* Allow lockless access for expedited grace periods. */ smp_store_release(&rcu_state.ncpus, rcu_state.ncpus + nbits); /* ^^^ */ + ASSERT_EXCLUSIVE_WRITER(rcu_state.ncpus); rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */ rdp->rcu_onl_gp_seq = READ_ONCE(rcu_state.gp_seq); rdp->rcu_onl_gp_flags = READ_ONCE(rcu_state.gp_flags); -- 2.9.5