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Mon, 05 Jan 2026 10:48:03 -0800 (PST) Received: from mozart.vkv.me ([2001:5a8:468b:d015:feec:4b73:3a24:90d5]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2b16f2eb216sm622252eec.31.2026.01.05.10.48.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 05 Jan 2026 10:48:03 -0800 (PST) Date: Mon, 5 Jan 2026 10:48:00 -0800 From: Calvin Owens To: Matthew Wilcox Cc: linux-mm@kvack.org, Andrew Morton , David Hildenbrand , Lorenzo Stoakes Subject: Re: [BUG next-20260105] khugepaged: kernel BUG at ./include/linux/xarray.h:1441 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: D0D0620004 X-Rspamd-Server: rspam04 X-Stat-Signature: k7hr4nbkt1smkjdxrigcn6ayqmgojdjg X-HE-Tag: 1767638884-780773 X-HE-Meta: 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 u2/u1Qa9 R5wBBtS5MbbiKo9n6oGGZ7tHBJfSP82jWngSYy6ynxHZWjj0x27nP9eLVIk0w/cTR8hHorQ57uGFguk+SNZznMr28W19H21GHW/mQkVrqP/N9OufWGiPSY/i4/cWVinbgE1P2mgKa3lseRAX3HpthGeT4vnJ+BDotRPWpiwRwr7QWz5ftfvhhNIdUrueiuoC8pe3QWzl/1wQUjm+03W6Yw0zrr9uWwYysDqFbd6q3R2Eo56/Zv9OgjAQcvO0vKDmm5s/nkMNkN2sEz/PuoaGgGHSkKEg87i4w8YDgMlAhG461yRAAQe2ANDoDZjiorPIFTmVggG732RW3kWCM9y5trjMm3vEIY48FZrcQ 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 Monday 01/05 at 18:24 +0000, Matthew Wilcox wrote: > On Mon, Jan 05, 2026 at 09:24:46AM -0800, Calvin Owens wrote: > > Hello all, > > > > I'm hitting this BUG_ON consistently after boot on next-20260105: > > > > [ 17.103774][ T40] node ffff888102d43918 offset 0 parent ffff888102d42920 shift 0 count 64 values 0 array ffff888107432e38 list ffff888102d43930 ffff888102d43930 marks 0 0 0 > > [ 17.108851][ T40] ------------[ cut here ]------------ > > [ 17.110476][ T40] kernel BUG at ./include/linux/xarray.h:1441! > > [ 17.112321][ T40] Oops: invalid opcode: 0000 [#1] SMP PTI > > [ 17.114177][ T40] CPU: 1 UID: 0 PID: 40 Comm: khugepaged Not tainted 6.19.0-rc4-next-20260105-x86-hardened-yugetlb #1 PREEMPTLAZY a1685c863f468289fb411d1c9b04bc9e336fe015 > > [ 17.118934][ T40] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-20240910_120124-localhost 04/01/2014 > > [ 17.122375][ T40] RIP: 0010:hpage_collapse_scan_file+0x1b05/0x1b30 > > Could you run this through ./scripts/decode_stacktrace.sh ? I'd like > to see which caller of xas_lock() triggered this. Something about the instruction decoding is broken with llvm, but it still pulls the line numbers out: {0}[calvinow@handel ~/git/linux] ./scripts/decode_stacktrace.sh vmlinux < ~/stack.txt [ 16.027866][ T58] kernel BUG at ./include/linux/xarray.h:1441! [ 16.030181][ T58] Oops: invalid opcode: 0000 [#1] SMP PTI [ 16.032294][ T58] CPU: 3 UID: 0 PID: 58 Comm: khugepaged Not tainted 6.19.0-rc4-next-20260105-x86-hardened-yugetlb #1 PREEMPTLAZY 9ffdba64952937e3f0143c6f15435a9a9e8ec86b [ 16.038092][ T58] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-20240910_120124-localhost 04/01/2014 [ 16.042275][ T58] RIP: 0010:hpage_collapse_scan_file (./include/linux/xarray.h:1441 mm/khugepaged.c:2042 mm/khugepaged.c:2389) [ 16.044711][ T58] Code: e8 d5 b2 ff ff 48 83 c4 18 65 ff 0d da c8 8e 01 0f 85 5a fe ff ff e8 6f 1b d6 ff e9 50 fe ff ff 48 85 ff 74 05 e8 80 4b 69 00 <0f> 0b 48 85 ff 74 05 e8 74 4b 69 00 0f 0b 48 85 ff 74 05 e8 68 4b objdump: error: '/tmp/tmp.oGg2U9eb6N.o': No such file or directory objdump: error: '/tmp/tmp.oGg2U9eb6N.o': No such file or directory All code ======== Code starting with the faulting instruction =========================================== [ 16.051928][ T58] RSP: 0018:ffffc900001ffca8 EFLAGS: 00010246 [ 16.054183][ T58] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 [ 16.056731][ T58] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 [ 16.058926][ T58] RBP: 0000000000000200 R08: 0000000000000000 R09: 0000000000000000 [ 16.061226][ T58] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 16.063446][ T58] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 16.065658][ T58] FS: 0000000000000000(0000) GS:ffff8882b4ff0000(0000) knlGS:0000000000000000 [ 16.068581][ T58] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 16.070783][ T58] CR2: 000076192552d16c CR3: 00000001398b6004 CR4: 0000000000170eb0 [ 16.073466][ T58] Call Trace: [ 16.074591][ T58] [ 16.075560][ T58] ? __cfi_workingset_update_node (mm/workingset.c:614) [ 16.077556][ T58] ? khugepaged (mm/khugepaged.c:2473 mm/khugepaged.c:2572 mm/khugepaged.c:2628) [ 16.079077][ T58] khugepaged (mm/khugepaged.c:2474 mm/khugepaged.c:2572 mm/khugepaged.c:2628) [ 16.080522][ T58] ? __cfi_khugepaged (mm/khugepaged.c:2621) [ 16.082140][ T58] kthread (kernel/kthread.c:469) [ 16.083529][ T58] ? __cfi_kthread (kernel/kthread.c:412) [ 16.085063][ T58] ret_from_fork (arch/x86/kernel/process.c:164) [ 16.086603][ T58] ? __cfi_kthread (kernel/kthread.c:412) [ 16.088156][ T58] ret_from_fork_asm (arch/x86/entry/entry_64.S:259) [ 16.089751][ T58] [ 16.090774][ T58] ---[ end trace 0000000000000000 ]--- [ 16.092603][ T58] RIP: 0010:hpage_collapse_scan_file (./include/linux/xarray.h:1441 mm/khugepaged.c:2042 mm/khugepaged.c:2389) [ 16.094787][ T58] Code: e8 d5 b2 ff ff 48 83 c4 18 65 ff 0d da c8 8e 01 0f 85 5a fe ff ff e8 6f 1b d6 ff e9 50 fe ff ff 48 85 ff 74 05 e8 80 4b 69 00 <0f> 0b 48 85 ff 74 05 e8 74 4b 69 00 0f 0b 48 85 ff 74 05 e8 68 4b objdump: error: '/tmp/tmp.iup3T2wP74.o': No such file or directory objdump: error: '/tmp/tmp.iup3T2wP74.o': No such file or directory All code ======== Code starting with the faulting instruction =========================================== [ 16.101366][ T58] RSP: 0018:ffffc900001ffca8 EFLAGS: 00010246 [ 16.103417][ T58] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 [ 16.106095][ T58] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 [ 16.108764][ T58] RBP: 0000000000000200 R08: 0000000000000000 R09: 0000000000000000 [ 16.111474][ T58] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 16.114304][ T58] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 16.117128][ T58] FS: 0000000000000000(0000) GS:ffff8882b4ff0000(0000) knlGS:0000000000000000 [ 16.120308][ T58] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 16.122638][ T58] CR2: 000076192552d16c CR3: 00000001398b6004 CR4: 0000000000170eb0 Thanks, Calvin