From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754356AbbLIXGQ (ORCPT ); Wed, 9 Dec 2015 18:06:16 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:48778 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753838AbbLIXDP (ORCPT ); Wed, 9 Dec 2015 18:03:15 -0500 X-IBM-Helo: d03dlp01.boulder.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: 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, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, "Paul E. McKenney" Subject: [PATCH v2 tip/core/rcu 01/11] rcu: Short-circuit synchronize_sched_expedited() if only one CPU Date: Wed, 9 Dec 2015 15:02:58 -0800 Message-Id: <1449702188-493-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 2.5.2 In-Reply-To: <20151209230243.GA32518@linux.vnet.ibm.com> References: <20151209230243.GA32518@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15120923-0013-0000-0000-00001AE8FD6E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If there is only one CPU, then invoking synchronize_sched_expedited() is by definition a grace period. This commit checks for this condition and does a short-circuit return in that case. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 81aa1cdc6bc9..bd2605c144cc 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3822,6 +3822,10 @@ void synchronize_sched_expedited(void) struct rcu_node *rnp; struct rcu_state *rsp = &rcu_sched_state; + /* If only one CPU, this is automatically a grace period. */ + if (rcu_blocking_is_gp()) + return; + /* Take a snapshot of the sequence number. */ s = rcu_exp_gp_seq_snap(rsp); -- 2.5.2