{"id":833371,"url":"http://patchwork.ozlabs.org/api/1.2/patches/833371/?format=json","web_url":"http://patchwork.ozlabs.org/project/ubuntu-kernel/patch/20171102140501.87671-11-gwalbon@linux.vnet.ibm.com/","project":{"id":15,"url":"http://patchwork.ozlabs.org/api/1.2/projects/15/?format=json","name":"Ubuntu Kernel","link_name":"ubuntu-kernel","list_id":"kernel-team.lists.ubuntu.com","list_email":"kernel-team@lists.ubuntu.com","web_url":null,"scm_url":null,"webscm_url":null,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20171102140501.87671-11-gwalbon@linux.vnet.ibm.com>","list_archive_url":null,"date":"2017-11-02T14:04:59","name":"[Artful,10/12] powerpc/perf: Fix for core/nest imc call trace on cpuhotplug","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"facbb62e8800a6403282d861660558570f0a56ac","submitter":{"id":71662,"url":"http://patchwork.ozlabs.org/api/1.2/people/71662/?format=json","name":"Gustavo Walbon","email":"gwalbon@linux.vnet.ibm.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/ubuntu-kernel/patch/20171102140501.87671-11-gwalbon@linux.vnet.ibm.com/mbox/","series":[{"id":11509,"url":"http://patchwork.ozlabs.org/api/1.2/series/11509/?format=json","web_url":"http://patchwork.ozlabs.org/project/ubuntu-kernel/list/?series=11509","date":"2017-11-02T14:04:50","name":"Backport for Power9 Nest PMU Instrumentation","version":1,"mbox":"http://patchwork.ozlabs.org/series/11509/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/833371/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/833371/checks/","tags":{},"related":[],"headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@bilbo.ozlabs.org","Authentication-Results":"ozlabs.org;\n\tspf=none (mailfrom) smtp.mailfrom=lists.ubuntu.com\n\t(client-ip=91.189.94.19; helo=huckleberry.canonical.com;\n\tenvelope-from=kernel-team-bounces@lists.ubuntu.com;\n\treceiver=)","Received":["from huckleberry.canonical.com (huckleberry.canonical.com\n\t[91.189.94.19])\n\tby ozlabs.org (Postfix) with ESMTP id 3ySRgg0P3gz9sNw;\n\tFri, 3 Nov 2017 01:05:35 +1100 (AEDT)","from localhost ([127.0.0.1] helo=huckleberry.canonical.com)\n\tby huckleberry.canonical.com with esmtp (Exim 4.86_2)\n\t(envelope-from )\n\tid 1eAG7f-0002RL-1H; Thu, 02 Nov 2017 14:05:31 +0000","from mx0a-001b2d01.pphosted.com ([148.163.156.1])\n\tby huckleberry.canonical.com with esmtps\n\t(TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2)\n\t(envelope-from ) id 1eAG7d-0002MK-2u\n\tfor kernel-team@lists.ubuntu.com; Thu, 02 Nov 2017 14:05:29 +0000","from pps.filterd (m0098393.ppops.net [127.0.0.1])\n\tby mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id\n\tvA2E4RnS081658\n\tfor ; Thu, 2 Nov 2017 10:05:27 -0400","from e12.ny.us.ibm.com (e12.ny.us.ibm.com [129.33.205.202])\n\tby mx0a-001b2d01.pphosted.com with ESMTP id 2e03jm5862-1\n\t(version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT)\n\tfor ; Thu, 02 Nov 2017 10:05:27 -0400","from localhost\n\tby e12.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use\n\tOnly! Violators will be prosecuted\n\tfor from ; \n\tThu, 2 Nov 2017 10:05:26 -0400","from b01cxnp23033.gho.pok.ibm.com (9.57.198.28)\n\tby e12.ny.us.ibm.com (146.89.104.199) with IBM ESMTP SMTP Gateway:\n\tAuthorized Use Only! Violators will be prosecuted; \n\tThu, 2 Nov 2017 10:05:23 -0400","from b01ledav005.gho.pok.ibm.com (b01ledav005.gho.pok.ibm.com\n\t[9.57.199.110])\n\tby b01cxnp23033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP\n\tid vA2E5Liv60293372; Thu, 2 Nov 2017 14:05:23 GMT","from b01ledav005.gho.pok.ibm.com (unknown [127.0.0.1])\n\tby IMSVA (Postfix) with ESMTP id 98354AE052;\n\tThu, 2 Nov 2017 10:06:09 -0400 (EDT)","from localhost (unknown [9.85.138.60])\n\tby b01ledav005.gho.pok.ibm.com (Postfix) with ESMTP id 09951AE03C;\n\tThu, 2 Nov 2017 10:06:08 -0400 (EDT)"],"From":"Gustavo Walbon ","To":"kernel-team@lists.ubuntu.com","Subject":"[Artful][PATCH 10/12] powerpc/perf: Fix for core/nest imc call trace\n\ton cpuhotplug","Date":"Thu, 2 Nov 2017 12:04:59 -0200","X-Mailer":"git-send-email 2.13.3","In-Reply-To":"<20171102140501.87671-1-gwalbon@linux.vnet.ibm.com>","References":"<20171102140501.87671-1-gwalbon@linux.vnet.ibm.com>","X-TM-AS-GCONF":"00","x-cbid":"17110214-0048-0000-0000-000001FF6938","X-IBM-SpamModules-Scores":"","X-IBM-SpamModules-Versions":"BY=3.00007997; HX=3.00000241; KW=3.00000007;\n\tPH=3.00000004; SC=3.00000239; SDB=6.00940090; UDB=6.00474019;\n\tIPR=6.00720346; \n\tBA=6.00005666; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009;\n\tZB=6.00000000; \n\tZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00017836;\n\tXFM=3.00000015; UTC=2017-11-02 14:05:24","X-IBM-AV-DETECTION":"SAVI=unused REMOTE=unused XFE=unused","x-cbparentid":"17110214-0049-0000-0000-0000430E79FF","Message-Id":"<20171102140501.87671-11-gwalbon@linux.vnet.ibm.com>","X-Proofpoint-Virus-Version":"vendor=fsecure engine=2.50.10432:, ,\n\tdefinitions=2017-11-02_05:, , signatures=0","X-Proofpoint-Spam-Details":"rule=outbound_notspam policy=outbound score=0\n\tpriorityscore=1501\n\tmalwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0\n\tclxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0\n\tclassifier=spam adjust=0 reason=mlx scancount=1\n\tengine=8.0.1-1707230000\n\tdefinitions=main-1711020178","X-BeenThere":"kernel-team@lists.ubuntu.com","X-Mailman-Version":"2.1.20","Precedence":"list","List-Id":"Kernel team discussions ","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","MIME-Version":"1.0","Content-Type":"text/plain; charset=\"utf-8\"","Content-Transfer-Encoding":"base64","Errors-To":"kernel-team-bounces@lists.ubuntu.com","Sender":"\"kernel-team\" "},"content":"From: Anju T Sudhakar \n\nBugLink: https://bugs.launchpad.net/bugs/1481347\n\nNest/core pmu units are enabled only when it is used. A reference count is\nmaintained for the events which uses the nest/core pmu units. Currently in\n*_imc_counters_release function a WARN() is used for notification of any\nunderflow of ref count.\n\nThe case where event ref count hit a negative value is, when perf session is\nstarted, followed by offlining of all cpus in a given core.\ni.e. in cpuhotplug offline path ppc_core_imc_cpu_offline() function set the\nref->count to zero, if the current cpu which is about to offline is the last\ncpu in a given core and make an OPAL call to disable the engine in that core.\nAnd on perf session termination, perf->destroy (core_imc_counters_release) will\nfirst decrement the ref->count for this core and based on the ref->count value\nan opal call is made to disable the core-imc engine.\nNow, since cpuhotplug path already clears the ref->count for core and disabled\nthe engine, perf->destroy() decrementing again at event termination make it\nnegative which in turn fires the WARN_ON. The same happens for nest units.\n\nAdd a check to see if the reference count is alreday zero, before decrementing\nthe count, so that the ref count will not hit a negative value.\n\nSigned-off-by: Anju T Sudhakar \nReviewed-by: Santosh Sivaraj \nSigned-off-by: Michael Ellerman \n(cherry-picked from 0d923820c6db1644c27c2d0a5af8920fc0f8cd81)\nSigned-off-by: Gustavo Walbon \n---\n arch/powerpc/perf/imc-pmu.c | 28 ++++++++++++++++++++++++++++\n 1 file changed, 28 insertions(+)","diff":"diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c\nindex 9ccac86f3463..e3a1f65933b5 100644\n--- a/arch/powerpc/perf/imc-pmu.c\n+++ b/arch/powerpc/perf/imc-pmu.c\n@@ -399,6 +399,20 @@ static void nest_imc_counters_release(struct perf_event *event)\n \n \t/* Take the mutex lock for this node and then decrement the reference count */\n \tmutex_lock(&ref->lock);\n+\tif (ref->refc == 0) {\n+\t\t/*\n+\t\t * The scenario where this is true is, when perf session is\n+\t\t * started, followed by offlining of all cpus in a given node.\n+\t\t *\n+\t\t * In the cpuhotplug offline path, ppc_nest_imc_cpu_offline()\n+\t\t * function set the ref->count to zero, if the cpu which is\n+\t\t * about to offline is the last cpu in a given node and make\n+\t\t * an OPAL call to disable the engine in that node.\n+\t\t *\n+\t\t */\n+\t\tmutex_unlock(&ref->lock);\n+\t\treturn;\n+\t}\n \tref->refc--;\n \tif (ref->refc == 0) {\n \t\trc = opal_imc_counters_stop(OPAL_IMC_COUNTERS_NEST,\n@@ -646,6 +660,20 @@ static void core_imc_counters_release(struct perf_event *event)\n \t\treturn;\n \n \tmutex_lock(&ref->lock);\n+\tif (ref->refc == 0) {\n+\t\t/*\n+\t\t * The scenario where this is true is, when perf session is\n+\t\t * started, followed by offlining of all cpus in a given core.\n+\t\t *\n+\t\t * In the cpuhotplug offline path, ppc_core_imc_cpu_offline()\n+\t\t * function set the ref->count to zero, if the cpu which is\n+\t\t * about to offline is the last cpu in a given core and make\n+\t\t * an OPAL call to disable the engine in that core.\n+\t\t *\n+\t\t */\n+\t\tmutex_unlock(&ref->lock);\n+\t\treturn;\n+\t}\n \tref->refc--;\n \tif (ref->refc == 0) {\n \t\trc = opal_imc_counters_stop(OPAL_IMC_COUNTERS_CORE,\n","prefixes":["Artful","10/12"]}