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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham 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 D1076C19759 for ; Thu, 1 Aug 2019 23:17:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ABCD62080C for ; Thu, 1 Aug 2019 23:17:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387447AbfHAXRO (ORCPT ); Thu, 1 Aug 2019 19:17:14 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:8076 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1733204AbfHAXRO (ORCPT ); Thu, 1 Aug 2019 19:17:14 -0400 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x71NDBav026681; Thu, 1 Aug 2019 19:16:38 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 2u486f2jxr-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 01 Aug 2019 19:16:38 -0400 Received: from m0098421.ppops.net (m0098421.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.27/8.16.0.27) with SMTP id x71NDDde027001; Thu, 1 Aug 2019 19:16:38 -0400 Received: from ppma02dal.us.ibm.com (a.bd.3ea9.ip4.static.sl-reverse.com [169.62.189.10]) by mx0a-001b2d01.pphosted.com with ESMTP id 2u486f2jx9-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 01 Aug 2019 19:16:37 -0400 Received: from pps.filterd (ppma02dal.us.ibm.com [127.0.0.1]) by ppma02dal.us.ibm.com (8.16.0.27/8.16.0.27) with SMTP id x71NG3kN012991; Thu, 1 Aug 2019 23:16:37 GMT Received: from b01cxnp23033.gho.pok.ibm.com (b01cxnp23033.gho.pok.ibm.com [9.57.198.28]) by ppma02dal.us.ibm.com with ESMTP id 2u0e85xguv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 01 Aug 2019 23:16:37 +0000 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp23033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x71NGaBK31195634 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 1 Aug 2019 23:16:36 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1AC4BB206A; Thu, 1 Aug 2019 23:16:36 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 00A46B206B; Thu, 1 Aug 2019 23:16:35 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.70.82.154]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Thu, 1 Aug 2019 23:16:35 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 2516416C9A51; Thu, 1 Aug 2019 16:16:37 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, 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, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 10/10] rcu/nocb: Unconditionally advance and wake for excessive CBs Date: Thu, 1 Aug 2019 16:16:35 -0700 Message-Id: <20190801231636.23115-10-paulmck@linux.ibm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190801231619.GA22610@linux.ibm.com> References: <20190801231619.GA22610@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-08-01_10:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=15 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908010245 Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org When there are excessive numbers of callbacks, and when either the corresponding no-CBs callback kthread is asleep or there is no more ready-to-invoke callbacks, and when least one callback is pending, __call_rcu_nocb_wake() will advance the callbacks, but refrain from awakening the corresponding no-CBs grace-period kthread. However, because rcu_advance_cbs_nowake() is used, it is possible (if a bit unlikely) that the needed advancement could not happen due to a grace period not being in progress. Plus there will always be at least one pending callback due to one having just now been enqueued. This commit therefore attempts to advance callbacks and awakens the no-CBs grace-period kthread when there are excessive numbers of callbacks posted and when the no-CBs callback kthread is not in a position to do anything helpful. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_plugin.h | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index af9cbc7d4784..e164d2c5fa93 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1666,13 +1666,19 @@ static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone, if (!rdp->nocb_cb_sleep && rcu_segcblist_ready_cbs(&rdp->cblist)) { // Already going full tilt, so don't try to rewake. - } else if (rcu_segcblist_pend_cbs(&rdp->cblist)) { - rcu_advance_cbs_nowake(rdp->mynode, rdp); + rcu_nocb_unlock_irqrestore(rdp, flags); } else { - wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE_FORCE, - TPS("WakeOvfIsDeferred")); + rcu_advance_cbs_nowake(rdp->mynode, rdp); + if (!irqs_disabled_flags(flags)) { + wake_nocb_gp(rdp, false, flags); + trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, + TPS("WakeOvf")); + } else { + wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE_FORCE, + TPS("WakeOvfIsDeferred")); + rcu_nocb_unlock_irqrestore(rdp, flags); + } } - rcu_nocb_unlock_irqrestore(rdp, flags); } else { trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WakeNot")); rcu_nocb_unlock_irqrestore(rdp, flags); -- 2.17.1