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b=qwL/7fDQeWrz5y/TUE+9vIi+MFL1G7OIkBoGGnwd6AWApsB/FNthMANluTL/vvBnB dVXL8dw04UmHs0P0xWW6zF1ViM7clnQI3WW8GBzhhRse7VsESi3YhOxq3U+eqvTIKf mZzF1OayOxRwORTdoUOACpn7keuKBrnXn0ERvzfhyuzZLh0KIP/CNas72X4+13k6jp J0ZU/Srs86bnHMIkGz7yNWAm0MLsbjtkstUSKmrvWu/J2iLAic1w2aBeG00Xcq+Pg4 DSR78rQ0wdMyWHx1Wc01TfTgijxFV7vxVB4oR8bs6PTi18zG5gfQmxoStaWVgAXzE3 3wvFipC+0194w== From: SeongJae Park To: Wei Yang Cc: SeongJae Park , akpm@linux-foundation.org, david@redhat.com, lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, xu.xin16@zte.com.cn, linux-mm@kvack.org, Kiryl Shutsemau Subject: Re: [Patch v2 2/2] mm/khugepaged: remove definition of struct khugepaged_mm_slot Date: Sat, 20 Sep 2025 06:41:30 -0700 Message-Id: <20250920134130.84541-1-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250920122958.nf6vcm6iyl2wz3bj@master> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 29C83140012 X-Rspamd-Server: rspam05 X-Stat-Signature: bw7e1up6ikyamjrfnb8pzhax31e3yrsn X-Rspam-User: X-HE-Tag: 1758375693-485623 X-HE-Meta: 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 FF1+G5g8 Ov8G0Adwzlei9KjeZelHw0jkEsQHms1hmJfSUdr9Krp7CBVqdt7ThyeuiK4yoo/ctcfCGtxD3waDVtDGYUahA18LxytNZJYFkJShkYgkoMXN74Di3ZOYR9FHWJsgdfbFN7MRqoVjR+hAeFdz9pe0yw19dXGOcox9XU+fjEEGsuI1Dck/4QW63AJjAvMN8Qn0Y5yZ8UPOrMLx9Hf8ZH+A6aD9Mr9is/6UmdxuclMjiy3Ac/kFe1GSN4qCB2l/2JmvAGjFBSsv7zPMmTBYifH3c6+IsIa1L5boVMhb6XCT9AziZTKl68Ux60z0EvLchSSNAaG5VGzzsQDrYTkl2MdHnD/qJF1FUw3rJxl4X 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: List-Subscribe: List-Unsubscribe: On Sat, 20 Sep 2025 12:29:58 +0000 Wei Yang wrote: > On Sat, Sep 20, 2025 at 04:52:33AM -0700, SeongJae Park wrote: > [...] > > > >On latest mm-new tree, I am getting below error while building UML mode kernel > >for kunit. And 'git bisect' points me this patch. I'm not familiar with this > >code and have no time to dive deep for now, so reporting first. > > Thanks for reporting. Thank you for fast reply! > > > > >Oops: general protection fault, probably for non-canonical adI > >[ 356.456907] CPU: 34 UID: 0 PID: 309 Comm: khugepaged Not tainted 6.17.0-rc4+ #370 PREEMPT(voluntary) > >[ 356.457702] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-4.el9 04/01/2014 > >[ 356.458484] RIP: 0010:collect_mm_slot (mm/khugepaged.c:1427) > > If my understanding is correct, the error happens in following code flow: > > khugepaged_scan_mm_slot() > mm = slot->mm; (1) > collect_mm_slot() > mm = slot->mm; (2) > > Looks the reason is slot is NULL at (2), but we have already accessed it at (1). > > Not find the cause yet. > > Would you mind sharing your UML config and test step? So that I can reproduce > it. To reproduce the issue, I do below: $ ./tools/testing/kunit/kunit.py run --kunitconfig mm/damon/tests Then the OOPs happens a few seconds aftr the kunit run, or during the kunit-purpose UML build. The issue sometimes doesn't happen or take time more than seconds. Since the code is related with khugepaged, apparently there are some timing factors. But I was able to reproduce about 3/4 times. It was also reproducible when I build and install kernel on my QEMU machine using 'make install'. Thanks, SJ [...]