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Thu, 10 Apr 2025 12:23:02 +0000 (GMT) Date: Thu, 10 Apr 2025 17:52:59 +0530 From: Aditya Gupta To: Gavin Shan Cc: Oscar Salvador , linux-mm@kvack.org, Andrew Morton , Danilo Krummrich , David Hildenbrand , Greg Kroah-Hartman , Mahesh J Salgaonkar , "Rafael J. Wysocki" , Sourabh Jain , linux-kernel@vger.kernel.org, Donet Tom Subject: Re: [REPORT] Softlockups on PowerNV with upstream Message-ID: References: <20250409180344.477916-1-adityag@linux.ibm.com> <675d6580-814f-4fae-9dc5-9470645adc07@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <675d6580-814f-4fae-9dc5-9470645adc07@redhat.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 72wWsvzQSRwO6SpG7SA_e4rX4N-_0D4U X-Proofpoint-ORIG-GUID: 72wWsvzQSRwO6SpG7SA_e4rX4N-_0D4U X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1095,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-04-10_02,2025-04-08_04,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=598 bulkscore=0 impostorscore=0 mlxscore=0 suspectscore=0 clxscore=1015 priorityscore=1501 spamscore=0 malwarescore=0 lowpriorityscore=0 adultscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2502280000 definitions=main-2504100086 X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 4D3B5100003 X-Stat-Signature: iam5uuzu8ifwd79beg1ek96iptxu8wgu X-HE-Tag: 1744287794-862630 X-HE-Meta: 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 PcoqkmGa VEwlKjXDJO35A1xO75err5+mrCpTS2s41Aw4IWRw+dzgVo2XsLA7TPzrpgTXlwFw2191Y7a43D3kTi3DfCW0/OihDxisYwsscZRBYr5PxCjL/UjeJ+fioPF81Y0Cjy69XMW7ImYNgILsP8AtYIxbYvfBS7+cgnBtrgUkKOBImbVFMoR4CImbtuD0vqiytiCRe3jZL4wYsX4GGPZQaRsV8kZXKHdL854vc1YqP X-Bogosity: Ham, tests=bogofilter, spamicity=0.121346, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Cc +donet On 25/04/10 07:44PM, Gavin Shan wrote: > On 4/10/25 6:23 PM, Oscar Salvador wrote: > > On Thu, Apr 10, 2025 at 03:35:19PM +1000, Gavin Shan wrote: > > > Thanks, Oscar. You're correct that the overhead is introduced by for_each_present_section_nr(). > > > I already had the fix, working on IBM's Power9 machine, where the issue can be > > > reproduced. Please see the attached patch. > > > > > > I'm having most tests on ARM64 machine for the fix. > > > > Looks good to me. > > But we need a comment explaining why block_id is set to ULONG_MAX > > at the beginning as this might not be obvious. > > > > Also, do we need > > if (block_id != ULONG_MAX && memory_block_id(nr) == block_id) ? > > > > Cannot just be > > > > if (memory_block_id(nr) == block_id) ? > > > > AFAICS, the first time we loop through 'memory_block_id(nr) == ULONG_MAX' > > will evaluate false and and we will set block_id afterwards. > > > > Either way looks fine to me. > > Another way I guess would be: > > > > Yeah, we need to record the last handled block ID by @block_id. For the > first time to register the block memory device in the loop, @block_id needs > to be invalid (ULONG_MAX), bypassing the check of 'memory_block_id(nr) == block_id'. > I will post the fix for review after Aditya confirms it works for him, with extra > comment to explain why @block_id is initialized to ULONG_MAX. > > Aditya, please have a try when you get a chance, thanks! I verified it on Power9 > machine where the issue exists and on one of my ARM64 machine. I don't see any softlockups now with your patch as well as Oscar's patch. Tested on PowerNV Power10. Thanks for the quick replies Gavin. - Aditya G > > Thanks, > Gavin >