From patchwork Fri May 10 09:24:54 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Gautham R Shenoy X-Patchwork-Id: 1097926 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 450lGw5HrPz9sCJ for ; Fri, 10 May 2019 19:27:20 +1000 (AEST) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.vnet.ibm.com Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 450lGw429vzDqV1 for ; Fri, 10 May 2019 19:27:20 +1000 (AEST) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; spf=none (mailfrom) smtp.mailfrom=linux.vnet.ibm.com (client-ip=148.163.158.5; helo=mx0a-001b2d01.pphosted.com; envelope-from=ego@linux.vnet.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.vnet.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 450lDd6jNBzDqT5 for ; Fri, 10 May 2019 19:25:21 +1000 (AEST) Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x4A9MjuE183035 for ; Fri, 10 May 2019 05:25:18 -0400 Received: from e35.co.us.ibm.com (e35.co.us.ibm.com [32.97.110.153]) by mx0b-001b2d01.pphosted.com with ESMTP id 2sd4ykcu3f-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 10 May 2019 05:25:18 -0400 Received: from localhost by e35.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 10 May 2019 10:25:15 +0100 Received: from b03ledav002.gho.boulder.ibm.com (b03ledav002.gho.boulder.ibm.com [9.17.130.233]) by b03cxnp08025.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x4A9PEct52953342 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 10 May 2019 09:25:14 GMT Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9062913605E; Fri, 10 May 2019 09:25:14 +0000 (GMT) Received: from b03ledav002.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4ADA513604F; Fri, 10 May 2019 09:25:14 +0000 (GMT) Received: from sofia.ibm.com (unknown [9.124.35.248]) by b03ledav002.gho.boulder.ibm.com (Postfix) with ESMTP; Fri, 10 May 2019 09:25:14 +0000 (GMT) Received: by sofia.ibm.com (Postfix, from userid 1000) id 1BA412E2D08; Fri, 10 May 2019 14:55:13 +0530 (IST) From: "Gautham R. Shenoy" To: Paul Mackerras , Nicholas Piggin , Michael Ellerman , "Aneesh Kumar K.V" Subject: [RESEND PATCH] powerpc/pseries: Fix cpu_hotplug_lock acquisition in resize_hpt Date: Fri, 10 May 2019 14:54:54 +0530 X-Mailer: git-send-email 1.8.3.1 X-TM-AS-GCONF: 00 x-cbid: 19051009-0012-0000-0000-000017349B09 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011081; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000285; SDB=6.01201230; UDB=6.00630345; IPR=6.00982126; MB=3.00026827; MTD=3.00000008; XFM=3.00000015; UTC=2019-05-10 09:25:17 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19051009-0013-0000-0000-000057358B3A Message-Id: <1557480294-808-1-git-send-email-ego@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-05-09_02:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 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-1905100067 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Gautham R. Shenoy" , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: "Gautham R. Shenoy" During a memory hotplug operations involving resizing of the HPT, we invoke a stop_machine() to perform the resizing. In this code path, we end up recursively taking the cpu_hotplug_lock, first in memory_hotplug_begin() and then subsequently in stop_machine(). This causes the system to hang. With lockdep enabled we get the following error message before the hang. swapper/0/1 is trying to acquire lock: (____ptrval____) (cpu_hotplug_lock.rw_sem){++++}, at: stop_machine+0x2c/0x60 but task is already holding lock: (____ptrval____) (cpu_hotplug_lock.rw_sem){++++}, at: mem_hotplug_begin+0x20/0x50 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(cpu_hotplug_lock.rw_sem); lock(cpu_hotplug_lock.rw_sem); *** DEADLOCK *** Fix this issue by 1) Requiring all the calls to pseries_lpar_resize_hpt() be made with cpu_hotplug_lock held. 2) In pseries_lpar_resize_hpt() invoke stop_machine_cpuslocked() as a consequence of 1) 3) To satisfy 1), in hpt_order_set(), call mmu_hash_ops.resize_hpt() with cpu_hotplug_lock held. Reported-by: Aneesh Kumar K.V Signed-off-by: Gautham R. Shenoy --- Rebased this one against powerpc/next instead of linux/master. arch/powerpc/mm/book3s64/hash_utils.c | 9 ++++++++- arch/powerpc/platforms/pseries/lpar.c | 8 ++++++-- 2 files changed, 14 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c index 919a861..d07fcafd 100644 --- a/arch/powerpc/mm/book3s64/hash_utils.c +++ b/arch/powerpc/mm/book3s64/hash_utils.c @@ -38,6 +38,7 @@ #include #include #include +#include #include #include @@ -1928,10 +1929,16 @@ static int hpt_order_get(void *data, u64 *val) static int hpt_order_set(void *data, u64 val) { + int ret; + if (!mmu_hash_ops.resize_hpt) return -ENODEV; - return mmu_hash_ops.resize_hpt(val); + cpus_read_lock(); + ret = mmu_hash_ops.resize_hpt(val); + cpus_read_unlock(); + + return ret; } DEFINE_DEBUGFS_ATTRIBUTE(fops_hpt_order, hpt_order_get, hpt_order_set, "%llu\n"); diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index 1034ef1..2fc9756 100644 --- a/arch/powerpc/platforms/pseries/lpar.c +++ b/arch/powerpc/platforms/pseries/lpar.c @@ -859,7 +859,10 @@ static int pseries_lpar_resize_hpt_commit(void *data) return 0; } -/* Must be called in user context */ +/* + * Must be called in user context. The caller should hold the + * cpus_lock. + */ static int pseries_lpar_resize_hpt(unsigned long shift) { struct hpt_resize_state state = { @@ -913,7 +916,8 @@ static int pseries_lpar_resize_hpt(unsigned long shift) t1 = ktime_get(); - rc = stop_machine(pseries_lpar_resize_hpt_commit, &state, NULL); + rc = stop_machine_cpuslocked(pseries_lpar_resize_hpt_commit, + &state, NULL); t2 = ktime_get();