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Sun, 21 Sep 2025 08:08:30 -0700 (PDT) Date: Sun, 21 Sep 2025 15:08:30 +0000 From: Wei Yang To: SeongJae Park Cc: Wei Yang , 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 Message-ID: <20250921150830.buufaqnc7x2zpdvo@master> Reply-To: Wei Yang References: <20250920122958.nf6vcm6iyl2wz3bj@master> <20250920134130.84541-1-sj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250920134130.84541-1-sj@kernel.org> User-Agent: NeoMutt/20170113 (1.7.2) X-Stat-Signature: bncinirsbxo5axy1mtejs5bmng66kd9k X-Rspamd-Queue-Id: 0035D180002 X-Rspam-User: X-Rspamd-Server: rspam03 X-HE-Tag: 1758467312-928255 X-HE-Meta: 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 89z0IsVI 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 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, Sep 20, 2025 at 06:41:30AM -0700, SeongJae Park wrote: >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. I run Qemu with kernel built from mm-new base commit b8086c280108 "drivers/base: move memory_block_add_nid() into the caller". Then run the kunit command above. Not see error for around 20 times of the test. Is my step correct? > >It was also reproducible when I build and install kernel on my QEMU machine >using 'make install'. > Run qemu with the same kernel and do "make clean && make all" several times. Not spot errors yet. kselftests/mm/khugepaged pass with this kernel. Will do kernel build for more time to see the effect. If my step is not correct, please let me know. > >Thanks, >SJ > >[...] -- Wei Yang Help you, Help me