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Thu, 21 Nov 2019 16:58:12 +0000 From: Roman Gushchin To: Christian Borntraeger CC: "akpm@linux-foundation.org" , "hannes@cmpxchg.org" , Kernel Team , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "longman@redhat.com" , "shakeelb@google.com" , "vdavydov.dev@gmail.com" , Heiko Carstens , Janosch Frank , "kvm@vger.kernel.org" Subject: Re: WARNING bisected (was Re: [PATCH v7 08/10] mm: rework non-root kmem_cache lifecycle management) Thread-Topic: WARNING bisected (was Re: [PATCH v7 08/10] mm: rework non-root kmem_cache lifecycle management) Thread-Index: AQHVoF1eUJGIXl/jo02oA2+fhmBRU6eV2PaA Date: Thu, 21 Nov 2019 16:58:11 +0000 Message-ID: <20191121165807.GA201621@localhost.localdomain> References: <20190611231813.3148843-9-guro@fb.com> <20191121111739.3054-1-borntraeger@de.ibm.com> In-Reply-To: <20191121111739.3054-1-borntraeger@de.ibm.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-clientproxiedby: CO1PR15CA0059.namprd15.prod.outlook.com (2603:10b6:101:1f::27) To BYAPR15MB2631.namprd15.prod.outlook.com (2603:10b6:a03:152::24) x-ms-exchange-messagesentrepresentingtype: 1 x-originating-ip: [2620:10d:c090:180::211b] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: bd361ef9-331c-4f0f-7b2d-08d76ea3fe1c x-ms-traffictypediagnostic: BYAPR15MB3318: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:3044; 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charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: bd361ef9-331c-4f0f-7b2d-08d76ea3fe1c X-MS-Exchange-CrossTenant-originalarrivaltime: 21 Nov 2019 16:58:12.0267 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: dIRlw15ZkPSSuXAdCFt4HLNsbpXW9MsNaz90DqRJG/wp2f4NZWYoTQGc7+zfYoau X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB3318 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-11-21_04:2019-11-21,2019-11-21 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 adultscore=0 mlxlogscore=664 impostorscore=0 phishscore=0 priorityscore=1501 lowpriorityscore=0 suspectscore=0 bulkscore=0 mlxscore=0 clxscore=1011 spamscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1911210148 X-FB-Internal: deliver X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Nov 21, 2019 at 12:17:39PM +0100, Christian Borntraeger wrote: > Folks, >=20 > I do get errors like the following when running a new testcase in our KVM= CI. > The test basically unloads kvm, reloads with with hpage=3D1 (enable huge = page > support for guests on s390) start a guest with libvirt and hugepages, shu= t the > guest down and unload the kvm module.=20 >=20 > WARNING: CPU: 8 PID: 208 at lib/percpu-refcount.c:108 percpu_ref_exit+0x5= 0/0x58 > Modules linked in: kvm(-) xt_CHECKSUM xt_MASQUERADE bonding xt_tcpudp ip6= t_rpfilter ip6t_REJECT nf_reject_ipv6 ipt_REJECT nf_reject_ipv4 xt_conntrac= k ip6table_na> > CPU: 8 PID: 208 Comm: kworker/8:1 Not tainted 5.2.0+ #66 > Hardware name: IBM 2964 NC9 712 (LPAR) > Workqueue: events sysfs_slab_remove_workfn > Krnl PSW : 0704e00180000000 0000001529746850 (percpu_ref_exit+0x50/0x58) > R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3 > Krnl GPRS: 00000000ffff8808 0000001529746740 000003f4e30e8e18 00360081000= 00000 > 0000001f00000000 0035008100000000 0000001fb3573ab8 00000000000= 00000 > 0000001fbdb6de00 0000000000000000 0000001529f01328 0000001fb35= 73b00 > 0000001fbb27e000 0000001fbdb69300 000003e009263d00 000003e0092= 63cd0 > Krnl Code: 0000001529746842: f0a0000407fe srp 4(11,%r0),204= 6,0 > 0000001529746848: 47000700 bc 0,1792 > #000000152974684c: a7f40001 brc 15,152974684e > >0000001529746850: a7f4fff2 brc 15,1529746834 > 0000001529746854: 0707 bcr 0,%r7 > 0000001529746856: 0707 bcr 0,%r7 > 0000001529746858: eb8ff0580024 stmg %r8,%r15,88(%= r15) > 000000152974685e: a738ffff lhi %r3,-1 > Call Trace: > ([<000003e009263d00>] 0x3e009263d00) > [<00000015293252ea>] slab_kmem_cache_release+0x3a/0x70=20 > [<0000001529b04882>] kobject_put+0xaa/0xe8=20 > [<000000152918cf28>] process_one_work+0x1e8/0x428=20 > [<000000152918d1b0>] worker_thread+0x48/0x460=20 > [<00000015291942c6>] kthread+0x126/0x160=20 > [<0000001529b22344>] ret_from_fork+0x28/0x30=20 > [<0000001529b2234c>] kernel_thread_starter+0x0/0x10=20 > Last Breaking-Event-Address: > [<000000152974684c>] percpu_ref_exit+0x4c/0x58 > ---[ end trace b035e7da5788eb09 ]--- >=20 > I have bisected this to > # first bad commit: [f0a3a24b532d9a7e56a33c5112b2a212ed6ec580] mm: memcg/= slab: rework non-root kmem_cache lifecycle management >=20 > unmounting /sys/fs/cgroup/memory/ before the test makes the problem go aw= ay so > it really seems to be related to the new percpu-refs from this patch. > =20 > Any ideas? Hello, Christian! It seems to be a race between releasing of the root kmem_cache (caused by r= mmod) and a memcg kmem_cache. Does delaying rmmod for say, a minute, "resolve" th= e issue? I'll take a look at this code path. Thanks!