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 76544C35242 for ; Fri, 14 Feb 2020 23:57:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 429AF206B6 for ; Fri, 14 Feb 2020 23:57:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581724675; bh=nYJGtkvt8mINfC95IpN7jOIxr7W0o0xbh3lQojeDMYk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=DzQJ+lhykX/J+JP9DtMiwA1wzs6pGDyNYn61Nz9Zi8zxWUCDlqVbELwwHtA27WIWM 26YfE5JUJokM/5OyHmYy2mstO4z2gPGjJRd7+kSLz16tuasDu5bZ8I1deXvXc3fP9x JIdfB6SLKgJnyk5egIRsZuJVoXTa1IQIHK8tUKKg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728475AbgBNX5y (ORCPT ); Fri, 14 Feb 2020 18:57:54 -0500 Received: from mail.kernel.org ([198.145.29.99]:37770 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727649AbgBNX5x (ORCPT ); Fri, 14 Feb 2020 18:57:53 -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 AB0D422314; Fri, 14 Feb 2020 23:57:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581724673; bh=nYJGtkvt8mINfC95IpN7jOIxr7W0o0xbh3lQojeDMYk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oAxHsCqNpIf5h8M6PLXXLPgJjMKRGmvLWKyTfqIY5xAqn624HIEAfzWZH6YEbuut3 in5hnrFAyDWfDgGJZ2sofyrr6H6PDlAyT7aOEr8KE8l02RcdHHAxHDQRW/4XtV7BPB pSbIakhFquvHm/2MUUJ+aq9yVnN6h/hOqN4yEn5M= 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 28/30] rcu: Mark rcu_state.ncpus to detect concurrent writes Date: Fri, 14 Feb 2020 15:56:05 -0800 Message-Id: <20200214235607.13749-28-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200214235536.GA13364@paulmck-ThinkPad-P72> References: <20200214235536.GA13364@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 4146207..3a60a160 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3397,6 +3397,7 @@ 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