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Wed, 17 Mar 2021 08:36:32 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.171.90.29]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 17 Mar 2021 08:36:31 +0000 (GMT) Subject: Re: [BUG -next] "memcg: charge before adding to swapcache on swapin" broken To: Heiko Carstens , Shakeel Butt Cc: Andrew Morton , Roman Gushchin , Johannes Weiner , Hugh Dickins , Juergen Christ , Vasily Gorbik , Linux MM , Linux-Next Mailing List , Stephen Rothwell References: From: Christian Borntraeger Message-ID: Date: Wed, 17 Mar 2021 09:36:31 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761 definitions=2021-03-17_02:2021-03-17,2021-03-17 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 malwarescore=0 mlxscore=0 clxscore=1011 suspectscore=0 adultscore=0 priorityscore=1501 phishscore=0 bulkscore=0 impostorscore=0 spamscore=0 mlxlogscore=933 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2103170065 X-Stat-Signature: rdt8nexo331c7wctsiuk8hhjt9naoetd X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 2A29FE0011E2 Received-SPF: none (de.ibm.com>: No applicable sender policy available) receiver=imf21; identity=mailfrom; envelope-from=""; helo=mx0a-001b2d01.pphosted.com; client-ip=148.163.158.5 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615970207-714138 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 17.03.21 01:46, Heiko Carstens wrote: > Hi Shakeel, > >>> your commit 3a9ca1b0ac0f ("memcg: charge before adding to swapcache on >>> swapin") in linux-next 20210316 appears to cause user process faults / >>> crashes on s390 like: >>> >>> User process fault: interruption code 003b ilc:3 in sshd[2aa15280000+df000] >>> Failing address: 0000000000000000 TEID: 0000000000000800 >>> Fault in primary space mode while using user ASCE. >>> AS:00000000966b41c7 R3:0000000000000024 >>> CPU: 0 PID: 401 Comm: sshd Not tainted 5.12.0-rc3-00048-geba7667a8534 #10 >>> Hardware name: IBM 8561 T01 703 (z/VM 7.2.0) >>> User PSW : 0705000180000000 0000000000000000 >>> R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:1 AS:0 CC:0 PM:0 RI:0 EA:3 >>> User GPRS: 0000000000000000 fffffffffffff000 0000000000000001 000002aa157b88f0 >>> 000002aa157c43c0 0000000000000000 0000000000000000 0000000000000000 >>> 0000000000000000 0000000000000000 0000000000000000 0000000000000000 >>> 0000000000000000 0000000000000000 0000000000000000 0000000000000000 >>> User Code: Bad PSW. >> >> Thanks for the report. Can you please explain a bit what the above report tells? > > Ah, sorry. This is the s390 output for exception-traces. That is if > /proc/sys/debug/exception-trace is set to one, and a process gets > killed because of an unhandled signal. > > In this particular case sshd was killed because it tried to access > address zero, where nothing is mapped. > > Given that all higher registers are zero in the register dump above my > guess would be this happened because a stack page got unmapped, and > when it got accessed to restore register contents a zero page was > mapped in instead of the real old page contents. > > We have also all other sorts of crashes in our CI with linux-next > currently, e.g. LTP's testcase "swapping01" seems to be able to make > (more or less) sure that the init process get's killed (-> panic). In other words it would be good if we could drop this patch from next until we have a fix. Otherwise we loose a lot of CI coverage for next.