From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756026AbaKERnN (ORCPT ); Wed, 5 Nov 2014 12:43:13 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:35394 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755479AbaKERln (ORCPT ); Wed, 5 Nov 2014 12:41:43 -0500 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, laijs@cn.fujitsu.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 tip/core/rcu 10/10] rcu: Don't initiate RCU priority boosting on root rcu_node Date: Wed, 5 Nov 2014 09:41:34 -0800 Message-Id: <1415209294-2534-10-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1415209294-2534-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20141105174109.GA1306@linux.vnet.ibm.com> <1415209294-2534-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14110517-0013-0000-0000-00000608C446 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" Because there is no longer any preempted tasks on the root rcu_node, and because there is no longer ever an rcub kthread for the root rcu_node, this commit drops the code in force_qs_rnp() that attempts to awaken the non-existent root rcub kthread. This is strictly a performance enhancement, removing a root rcu_node ->lock acquisition and release along with some tests in rcu_initiate_boost(), ending with the test that notes that there is no rcub kthread. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 3c23e921b438..d574f65ac023 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2481,12 +2481,6 @@ static void force_qs_rnp(struct rcu_state *rsp, } raw_spin_unlock_irqrestore(&rnp->lock, flags); } - rnp = rcu_get_root(rsp); - if (rnp->qsmask == 0) { - raw_spin_lock_irqsave(&rnp->lock, flags); - smp_mb__after_unlock_lock(); - rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */ - } } /* -- 1.8.1.5