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 AE28AC4360F for ; Tue, 2 Apr 2019 14:38:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 89E5920882 for ; Tue, 2 Apr 2019 14:38:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731992AbfDBOit (ORCPT ); Tue, 2 Apr 2019 10:38:49 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:41828 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1731396AbfDBOir (ORCPT ); Tue, 2 Apr 2019 10:38:47 -0400 Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x32EXtDx022720 for ; Tue, 2 Apr 2019 10:38:46 -0400 Received: from e15.ny.us.ibm.com (e15.ny.us.ibm.com [129.33.205.205]) by mx0a-001b2d01.pphosted.com with ESMTP id 2rm8p2v7aj-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 02 Apr 2019 10:38:46 -0400 Received: from localhost by e15.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 2 Apr 2019 15:38:45 +0100 Received: from b01cxnp22035.gho.pok.ibm.com (9.57.198.25) by e15.ny.us.ibm.com (146.89.104.202) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 2 Apr 2019 15:38:40 +0100 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 x32EcdWc26083378 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 2 Apr 2019 14:38:39 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 51469B206E; Tue, 2 Apr 2019 14:38:39 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2F91EB206A; Tue, 2 Apr 2019 14:38:39 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.70.82.188]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Tue, 2 Apr 2019 14:38:39 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 4C47316C1EAE; Tue, 2 Apr 2019 07:38:44 -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 RFC v2 tip/core/rcu 4/4] rcu: Allow rcu_read_unlock_special() to raise_softirq() if in_irq() Date: Tue, 2 Apr 2019 07:38:42 -0700 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190402143758.GA15134@linux.ibm.com> References: <20190402143758.GA15134@linux.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 19040214-0068-0000-0000-000003AF74A6 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010860; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000284; SDB=6.01183287; UDB=6.00619479; IPR=6.00964035; MB=3.00026260; MTD=3.00000008; XFM=3.00000015; UTC=2019-04-02 14:38:44 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19040214-0069-0000-0000-000048048791 Message-Id: <20190402143842.16068-4-paulmck@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-04-02_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=13 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=888 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904020099 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When running in an interrupt handler, raise_softirq() and raise_softirq_irqoff() have extremely low overhead: They simply set a bit in a per-CPU mask, which is checked upon exit from that interrupt handler. Therefore, if rcu_read_unlock_special() is invoked within an interrupt handler and RCU_SOFTIRQ is in use, this commit make use of raise_softirq_irqoff() even if there is no expedited grace period in flight and even if this is not a nohz_full CPU. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_plugin.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index d15cdab6aeb4..e1005f5e8094 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -615,7 +615,7 @@ static void rcu_read_unlock_special(struct task_struct *t) (rdp->grpmask & rnp->expmask) || tick_nohz_full_cpu(rdp->cpu); // Need to defer quiescent state until everything is enabled. - if (exp && irqs_were_disabled && use_softirq && + if ((exp || in_irq()) && irqs_were_disabled && use_softirq && (in_irq() || !t->rcu_read_unlock_special.b.deferred_qs)) { // Using softirq, safe to awaken, and we get // no help from enabling irqs, unlike bh/preempt. -- 2.17.1