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=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 5ED17C433E1 for ; Wed, 12 Aug 2020 22:57:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3159A22BF3 for ; Wed, 12 Aug 2020 22:57:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597273070; bh=8dX/jRRGYYoVQ4sfHAistYqVItFs5RRYfTXsC/iWNDc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=LNUEfd/cIsJiUNs3FqZ489M/ZI4tn/PJ/PgqbRRnG7J8jYA75lY0QIISXELuCSetM ZO5a/0BkJBFRk8SGgMHQkTaQwko6QTYs68N70xY8oF2R4TZWvo8h/ezBF/HYaq7qn2 rtXPZEPFTSL4wbd7b53SQPSW/doj1eokepY9uxic= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726680AbgHLW5h (ORCPT ); Wed, 12 Aug 2020 18:57:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:48996 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726637AbgHLW5g (ORCPT ); Wed, 12 Aug 2020 18:57:36 -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 0BC6322B45; Wed, 12 Aug 2020 22:57:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597273056; bh=8dX/jRRGYYoVQ4sfHAistYqVItFs5RRYfTXsC/iWNDc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eH9fW6h9Wp+mfejJk2PkC/aBga5X9fiV+ho31fP6NlqWsVTUx6pHesSCvRIjz0w+j qeLyD1wF7BOnF+tKc2mYyQQgWKN+CwZWjiNqteII9XAM7DYNz+4imJ4A9Nil4qw1FS YOY8vKYopXKqZ5dHqw6LRsbML1HE4rwbVe+hodR4= 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, elver@google.com, dvyukov@google.com, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 08/12] rcu: IPI all CPUs at GP start for strict GPs Date: Wed, 12 Aug 2020 15:57:28 -0700 Message-Id: <20200812225732.20068-8-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20200812225632.GA19759@paulmck-ThinkPad-P72> References: <20200812225632.GA19759@paulmck-ThinkPad-P72> Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@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 4353a1a..a30d6f3 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1678,6 +1678,15 @@ 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) @@ -1805,6 +1814,10 @@ 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