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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 14 Jan 2019 18:11:46 -0000 Received: from b01ledav004.gho.pok.ibm.com (b01ledav004.gho.pok.ibm.com [9.57.199.109]) by b01cxnp22035.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x0EIBjHb25821412 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 14 Jan 2019 18:11:45 GMT Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 85730112065; Mon, 14 Jan 2019 18:11:45 +0000 (GMT) Received: from b01ledav004.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 07756112064; Mon, 14 Jan 2019 18:11:45 +0000 (GMT) Received: from oc8380061452.ibm.com (unknown [9.53.179.183]) by b01ledav004.gho.pok.ibm.com (Postfix) with ESMTP; Mon, 14 Jan 2019 18:11:44 +0000 (GMT) Subject: Re: [PATCH] pseries/hotplug: Add more delay in pseries_cpu_die while waiting for rtas-stop To: ego@linux.vnet.ibm.com, Thiago Jung Bauermann Cc: linux-kernel@vger.kernel.org, Nicholas Piggin , Tyrel Datwyler , linuxppc-dev@lists.ozlabs.org References: <1544095908-2414-1-git-send-email-ego@linux.vnet.ibm.com> <87a7li5zv2.fsf@morokweng.localdomain> <20181207104311.GA11431@in.ibm.com> <20181207120346.GB11431@in.ibm.com> <87va443fm3.fsf@morokweng.localdomain> <20190109060823.GA20248@in.ibm.com> From: Michael Bringmann Openpgp: preference=signencrypt Autocrypt: addr=mwb@linux.vnet.ibm.com; prefer-encrypt=mutual; keydata= mQENBFcY7GcBCADzw3en+yzo9ASFGCfldVkIg95SAMPK0myXp2XJYET3zT45uBsX/uj9/2nA lBmXXeOSXnPfJ9V3vtiwcfATnWIsVt3tL6n1kqikzH9nXNxZT7MU/7gqzWZngMAWh/GJ9qyg DTOZdjsvdUNUWxtiLvBo7y+reA4HjlQhwhYxxvCpXBeRoF0qDWfQ8DkneemqINzDZPwSQ7zY t4F5iyN1I9GC5RNK8Y6jiKmm6bDkrrbtXPOtzXKs0J0FqWEIab/u3BDrRP3STDVPdXqViHua AjEzthQbGZm0VCxI4a7XjMi99g614/qDcXZCs00GLZ/VYIE8hB9C5Q+l66S60PLjRrxnABEB AAG0LU1pY2hhZWwgVy4gQnJpbmdtYW5uIDxtd2JAbGludXgudm5ldC5pYm0uY29tPokBOAQT AQIAIgUCVxjsZwIbAwYLCQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQSEdag3dpuTI0NAf8 CKYTDKQLgOSjVrU2L5rM4lXaJRmQV6oidD3vIhKSnWRvPq9C29ifRG6ri20prTHAlc0vycgm 41HHg0y2vsGgNXGTWC2ObemoZBI7mySXe/7Tq5mD/semGzOp0YWZ7teqrkiSR8Bw0p+LdE7K QmT7tpjjvuhrtQ3RRojUYcuy1nWUsc4D+2cxsnZslsx84FUKxPbLagDgZmgBhUw/sUi40s6S AkdViVCVS0WANddLIpG0cfdsV0kCae/XdjK3mRK6drFKv1z+QFjvOhc8QIkkxFD0da9w3tJj oqnqHFV5gLcHO6/wizPx/NV90y6RngeBORkQiRFWxTXS4Oj9GVI/UrkBDQRXGOxnAQgAmJ5Y ikTWrMWPfiveUacETyEhWVl7u8UhZcx3yy2te8O0ay7t9fYcZgIEfQPPVVus89acIXlG3wYL DDPvb21OprLxi+ZJ2a0S5we+LcSWN1jByxJlbWBq+/LcMtGAOhNLpysY1gD0Y4UW/eKS+TFZ 562qKC3k1dBvnV9JXCgeS1taYFxRdVAn+2DwK3nuyG/DDq/XgJ5BtmyC3MMx8CiW3POj+O+l 6SedIeAfZlZ7/xhijx82g93h07VavUQRwMZgZFsqmuxBxVGiav2HB+dNvs3PFB087Pvc9OHe qhajPWOP/gNLMmvBvknn1NToM9a8/E8rzcIZXoYs4RggRRYh6wARAQABiQEfBBgBAgAJBQJX GOxnAhsMAAoJEEhHWoN3abky+RUH/jE08/r5QzaNKYeVhu0uVbgXu5fsxqr2cAxhf+KuwT3T efhEP2alarxzUZdEh4MsG6c+X2NYLbD3cryiXxVx/7kSAJEFQJfA5P06g8NLR25Qpq9BLsN7 ++dxQ+CLKzSEb1X24hYAJZpOhS8ev3ii+M/XIo+olDBKuTaTgB6elrg3CaxUsVgLBJ+jbRkW yQe2S5f/Ja1ThDpSSLLWLiLK/z7+gaqwhnwjQ8Z8Y9D2itJQcj4itHilwImsqwLG7SxzC0NX IQ5KaAFYdRcOgwR8VhhkOIVd70ObSZU+E4pTET1WDz4o65xZ89yfose1No0+r5ht/xWOOrh8 53/hcWvxHVs= Organization: IBM Linux Technology Center Date: Mon, 14 Jan 2019 12:11:44 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190109060823.GA20248@in.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19011418-0064-0000-0000-000003968DAD X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010405; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000274; SDB=6.01146449; UDB=6.00597106; IPR=6.00926735; MB=3.00025124; MTD=3.00000008; XFM=3.00000015; UTC=2019-01-14 18:11:47 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19011418-0065-0000-0000-00003C08CF7F Message-Id: <74b2262b-48e7-b2a5-7d20-dc7f590958d9@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-01-14_10:,, 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-1901140144 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/9/19 12:08 AM, Gautham R Shenoy wrote: > I did some testing during the holidays. Here are the observations: > > 1) With just your patch (without any additional debug patch), if I run > DLPAR on /off operations on a system that has SMT=off, I am able to > see a crash involving RTAS stack corruption within an hour's time. > > 2) With the debug patch (appended below) which has additional debug to > capture the callers of stop-self, start-cpu, set-power-levels, the > system is able to perform DLPAR on/off operations on a system with > SMT=off for three days. And then, it crashed with the dead CPU showing > a "Bad kernel stack pointer". From this log, I can clearly > see that there were no concurrent calls to stop-self, start-cpu, > set-power-levels. The only concurrent RTAS calls were the dying CPU > calling "stop-self", and the CPU running the DLPAR operation calling > "query-cpu-stopped-state". The crash signature is appended below as > well. > > 3) Modifying your patch to remove the udelay and increase the loop > count from 25 to 1000 doesn't improve the situation. We are still able > to see the crash. > > 4) With my patch, even without any additional debug, I was able to > observe the system run the tests successfully for over a week (I > started the tests before the Christmas weekend, and forgot to turn it > off!) So does this mean that the problem is fixed with your patch? > > It appears that there is a narrow race window involving rtas-stop-self > and rtas-query-cpu-stopped-state calls that can be observed with your > patch. Adding any printk's seems to reduce the probability of hitting > this race window. It might be worth the while to check with RTAS > folks, if they suspect something here. What would the RTAS folks be looking at here? The 'narrow race window' is with respect to a patch that it sound like we should not be using. Thanks. Michael -- Michael W. Bringmann Linux Technology Center IBM Corporation Tie-Line 363-5196 External: (512) 286-5196 Cell: (512) 466-0650 mwb@linux.vnet.ibm.com