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=-13.1 required=3.0 tests=BAYES_00,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 AFD96C433E7 for ; Mon, 31 Aug 2020 18:11:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 85BAD2083E for ; Mon, 31 Aug 2020 18:11:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598897499; bh=NcJJDjKPbJHUqCWQSv0m7YSMWH5nrU0mAQI5DfMA5YU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=T6KM71p8pHqkDXAG9IBrjZyQu5wjh9p4tEIve/EL297GVhna/S9IKFTK1fQ7IAMRY WuJnop2hVZnsbCH4SrScZjajIf7RCqndMHdlhwzDTv8yE9qQAp5LkYkITjhTNU5mtn DxpS6usWcYN3047n1x2Kaz5b8gUX8MHCNZNe+GbM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729569AbgHaSLi (ORCPT ); Mon, 31 Aug 2020 14:11:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:36200 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729198AbgHaSL0 (ORCPT ); Mon, 31 Aug 2020 14:11:26 -0400 Received: from paulmck-ThinkPad-P72.home (unknown [50.45.173.55]) (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 5D05A214D8; Mon, 31 Aug 2020 18:11:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598897483; bh=NcJJDjKPbJHUqCWQSv0m7YSMWH5nrU0mAQI5DfMA5YU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hzm+EwNk1Eg6HPojLgueCwlma5KIffWsm2goG97DboPk81YZLY3C+6Pq2tIlyx6DF SsVfZexMjfhgBRFBfdtnqD4A93KZSQMiCNLSYWJhrHtcVu9PgMou6sp5eFrhPjwgeU FU7u+96iHf9HZ9zx0FGEIMzWs3UMckRd4+HM3txU= 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 08/13] rcu: IPI all CPUs at GP start for strict GPs Date: Mon, 31 Aug 2020 11:11:15 -0700 Message-Id: <20200831181120.1044-8-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200831181101.GA950@paulmck-ThinkPad-P72> References: <20200831181101.GA950@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" Currently, each CPU discovers the beginning of a given grace period on its own time, which is again good for efficiency but bad for fast grace periods. This commit therefore uses on_each_cpu() to IPI each CPU after grace-period initialization in order to inform each CPU of the new grace period in a timely manner, but only in kernels build with CONFIG_RCU_STRICT_GRACE_PERIOD=y. Reported-by Jann Horn Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 36a860c..88f4fa6 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1696,6 +1696,15 @@ static void rcu_gp_torture_wait(void) } /* + * Handler for on_each_cpu() to invoke the target CPU's RCU core + * processing. + */ +static void rcu_strict_gp_boundary(void *unused) +{ + invoke_rcu_core(); +} + +/* * Initialize a new grace period. Return false if no grace period required. */ static bool rcu_gp_init(void) @@ -1823,6 +1832,10 @@ static bool rcu_gp_init(void) WRITE_ONCE(rcu_state.gp_activity, jiffies); } + // If strict, make all CPUs aware of new grace period. + if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) + on_each_cpu(rcu_strict_gp_boundary, NULL, 0); + return true; } -- 2.9.5