From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161161AbcFOVrr (ORCPT ); Wed, 15 Jun 2016 17:47:47 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:27751 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753648AbcFOVqU (ORCPT ); Wed, 15 Jun 2016 17:46:20 -0400 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oleg@redhat.com, bobby.prani@gmail.com, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 01/12] rcu: Fix outdated rcu_scheduler_active comment Date: Wed, 15 Jun 2016 14:46:02 -0700 X-Mailer: git-send-email 2.5.2 In-Reply-To: <20160615214550.GA4931@linux.vnet.ibm.com> References: <20160615214550.GA4931@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16061521-0028-0000-0000-000004F6CE43 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16061521-0029-0000-0000-00002CB25BCE Message-Id: <1466027173-5501-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-06-15_13:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=1 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1606150231 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The comment header for rcu_scheduler_active states that it is used to optimize synchronize_sched() at early boot. This is incorrect. The synchronize_sched() function instead checks the number of online CPUs. This commit therefore replaces the comment's synchronize_sched() with synchronize_rcu(), which really does use rcu_scheduler_active for this purpose. Reported-by: Lihao Liang Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index c7f1bc4f817c..0fa692f1094e 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -130,7 +130,7 @@ int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ * The rcu_scheduler_active variable transitions from zero to one just * before the first task is spawned. So when this variable is zero, RCU * can assume that there is but one task, allowing RCU to (for example) - * optimize synchronize_sched() to a simple barrier(). When this variable + * optimize synchronize_rcu() to a simple barrier(). When this variable * is one, RCU must actually do all the hard work required to detect real * grace periods. This variable is also used to suppress boot-time false * positives from lockdep-RCU error checking. -- 2.5.2