From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755719AbcHVPXc (ORCPT ); Mon, 22 Aug 2016 11:23:32 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:40945 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755379AbcHVPXE (ORCPT ); Mon, 22 Aug 2016 11:23:04 -0400 X-IBM-Helo: d03dlp01.boulder.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com 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 6/6] rcu: Use RCU's online-CPU state for expedited IPI retry Date: Mon, 22 Aug 2016 08:23:07 -0700 X-Mailer: git-send-email 2.5.2 In-Reply-To: <20160822152239.GA7153@linux.vnet.ibm.com> References: <20160822152239.GA7153@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16082215-0024-0000-0000-000014618EDF X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00005629; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000183; SDB=6.00748116; UDB=6.00353034; IPR=6.00520781; BA=6.00004672; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00012420; XFM=3.00000011; UTC=2016-08-22 15:23:01 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16082215-0025-0000-0000-000043C788C7 Message-Id: <1471879387-7902-6-git-send-email-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-08-22_07:,, 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-1608220159 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This commit improves the accuracy of the interaction between CPU hotplug operations and RCU's expedited grace periods by using RCU's online-CPU state to determine when failed IPIs should be retried. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_exp.h | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 3bc4b3dda801..24343eb87b58 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -385,17 +385,16 @@ retry_ipi: mask_ofl_ipi &= ~mask; continue; } - /* Failed, raced with offline. */ + /* Failed, raced with CPU hotplug operation. */ raw_spin_lock_irqsave_rcu_node(rnp, flags); - if (cpu_online(cpu) && + if ((rnp->qsmaskinitnext & mask) && (rnp->expmask & mask)) { + /* Online, so delay for a bit and try again. */ raw_spin_unlock_irqrestore_rcu_node(rnp, flags); schedule_timeout_uninterruptible(1); - if (cpu_online(cpu) && - (rnp->expmask & mask)) - goto retry_ipi; - raw_spin_lock_irqsave_rcu_node(rnp, flags); + goto retry_ipi; } + /* CPU really is offline, so we can ignore it. */ if (!(rnp->expmask & mask)) mask_ofl_ipi &= ~mask; raw_spin_unlock_irqrestore_rcu_node(rnp, flags); -- 2.5.2