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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 02290C433F5 for ; Wed, 29 Aug 2018 21:17:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B77C620647 for ; Wed, 29 Aug 2018 21:17:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B77C620647 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.vnet.ibm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729095AbeH3BQP (ORCPT ); Wed, 29 Aug 2018 21:16:15 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:55962 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728699AbeH3BQN (ORCPT ); Wed, 29 Aug 2018 21:16:13 -0400 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 w7TL8n7A055931 for ; Wed, 29 Aug 2018 17:17:30 -0400 Received: from e16.ny.us.ibm.com (e16.ny.us.ibm.com [129.33.205.206]) by mx0a-001b2d01.pphosted.com with ESMTP id 2m61jbuy02-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 29 Aug 2018 17:17:29 -0400 Received: from localhost by e16.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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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 1/6] doc: Add design documentation on interruption of NMI handlers Date: Wed, 29 Aug 2018 14:17:17 -0700 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180829211637.GA20980@linux.vnet.ibm.com> References: <20180829211637.GA20980@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18082921-0072-0000-0000-000003996243 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009636; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000266; SDB=6.01080717; UDB=6.00557481; IPR=6.00860703; MB=3.00023001; MTD=3.00000008; XFM=3.00000015; UTC=2018-08-29 21:17:27 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18082921-0073-0000-0000-0000493E8E1C Message-Id: <20180829211722.21694-1-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-08-29_04:,, 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=882 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1808290206 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Make Requirements.html talk about how NMI handlers can take what appear to RCU to be normal interrupts. Signed-off-by: Paul E. McKenney --- .../RCU/Design/Requirements/Requirements.html | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html index 49690228b1c6..089a8e8faac1 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.html +++ b/Documentation/RCU/Design/Requirements/Requirements.html @@ -2275,6 +2275,17 @@ he also kindly surprised me with an algorithm that meets this requirement. +

+Furthermore, NMI handlers can be interrupted by what appear to RCU +to be normal interrupts. +One way that this can happen is for code that directly invokes +rcu_irq_enter() and rcu_irq_exit() to be called +from an NMI handler. +This astonishing fact of life prompted the current code structure, +which has rcu_irq_enter() invoking rcu_nmi_enter() +and rcu_irq_exit() invoking rcu_nmi_exit(). +And yes, I also learned of this requirement the hard way. +

Loadable Modules

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