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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 78FDAC43387 for ; Wed, 9 Jan 2019 21:19:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4EF6B206B6 for ; Wed, 9 Jan 2019 21:19:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726760AbfAIVTA (ORCPT ); Wed, 9 Jan 2019 16:19:00 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:54402 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726072AbfAIVTA (ORCPT ); Wed, 9 Jan 2019 16:19:00 -0500 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id x09LIjpb053529 for ; Wed, 9 Jan 2019 16:18:58 -0500 Received: from e14.ny.us.ibm.com (e14.ny.us.ibm.com [129.33.205.204]) by mx0a-001b2d01.pphosted.com with ESMTP id 2pwqsvadta-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 09 Jan 2019 16:18:58 -0500 Received: from localhost by e14.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 9 Jan 2019 21:18:57 -0000 Received: from b01cxnp22035.gho.pok.ibm.com (9.57.198.25) by e14.ny.us.ibm.com (146.89.104.201) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 9 Jan 2019 21:18:53 -0000 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp22035.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x09LIqCT16121942 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 9 Jan 2019 21:18:52 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9BEC5B2065; Wed, 9 Jan 2019 21:18:52 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7BB7CB2068; Wed, 9 Jan 2019 21:18:52 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.70.82.88]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Wed, 9 Jan 2019 21:18:52 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 4F4ED16C63C9; Wed, 9 Jan 2019 13:18:52 -0800 (PST) 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, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 04/12] rcu: Make expedited IPI handler return after handling critical section Date: Wed, 9 Jan 2019 13:18:42 -0800 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190109211830.GA30595@linux.ibm.com> References: <20190109211830.GA30595@linux.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 19010921-0052-0000-0000-00000375B42A X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010374; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000274; SDB=6.01144141; UDB=6.00595707; IPR=6.00924404; MB=3.00025056; MTD=3.00000008; XFM=3.00000015; UTC=2019-01-09 21:18:57 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19010921-0053-0000-0000-00005F678FF4 Message-Id: <20190109211850.31599-4-paulmck@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-01-09_10:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 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=8.0.1-1810050000 definitions=main-1901090170 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org During expedited RCU grace-period initialization, IPIs are sent to all non-idle online CPUs. The IPI handler checks to see if the CPU is in quiescent state, reporting one if so. This handler looks at three different cases: (1) The CPU is not in an rcu_read_lock()-based critical section, (2) The CPU is in the process of exiting an rcu_read_lock()-based critical section, and (3) The CPU is in an rcu_read_lock()-based critical section. In case (2), execution falls through into case (3). This is harmless from a functionality viewpoint, but can result in needless overhead during an improbable corner case. This commit therefore adds the "return" statement needed to prevent fall-through. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_exp.h | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 928fe5893a57..6d4eb4694b6f 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -697,6 +697,7 @@ static void sync_rcu_exp_handler(void *unused) WRITE_ONCE(t->rcu_read_unlock_special.b.exp_hint, true); } raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; } /* -- 2.17.1