INFO: task hung in hpage_collapse_scan_pmd

Status: upstream: reported on 2026/08/23 05:16
Reported-by: syzbot+0a1d46710b2d759e25af@syzkaller.appspotmail.com
First crash: 57d, last: 2d18h
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: task hung in hpage_collapse_scan_pmd 1 3 2d19h 25d 0/3 upstream: reported on 2026/09/23 12:03
upstream INFO: task hung in hpage_collapse_scan_pmd (2) mm 1 1 452d 452d 0/29 auto-obsoleted due to no activity on 2025/09/21 11:57
upstream INFO: task hung in hpage_collapse_scan_pmd mm 1 11 825d 828d 0/29 auto-obsoleted due to no activity on 2024/08/25 07:53
upstream INFO: task hung in hpage_collapse_scan_pmd (3) kasan mm 1 1 217d 217d 0/29 auto-obsoleted due to no activity on 2026/05/14 12:47

Sample crash report:
INFO: task khugepaged:35 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:khugepaged      state:D stack:27880 pid:35    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6834
 rwsem_down_write_slowpath+0xc3f/0x1020 kernel/locking/rwsem.c:1178
 __down_write_common kernel/locking/rwsem.c:1306 [inline]
 __down_write kernel/locking/rwsem.c:1315 [inline]
 down_write+0x1b9/0x200 kernel/locking/rwsem.c:1574
 mmap_write_lock include/linux/mmap_lock.h:108 [inline]
 collapse_huge_page mm/khugepaged.c:1133 [inline]
 hpage_collapse_scan_pmd+0x216a/0x4050 mm/khugepaged.c:1393
 khugepaged_scan_mm_slot mm/khugepaged.c:2411 [inline]
 khugepaged_do_scan mm/khugepaged.c:2499 [inline]
 khugepaged+0x8df/0x1520 mm/khugepaged.c:2555
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
INFO: task kworker/u4:4:59 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:4    state:D stack:22040 pid:59    ppid:2      flags:0x00004000
Workqueue: writeback wb_workfn (flush-8:0)
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 io_schedule+0x80/0xd0 kernel/sched/core.c:9024
 rq_qos_wait+0x22b/0x360 block/blk-rq-qos.c:282
 __wbt_wait block/blk-wbt.c:595 [inline]
 wbt_wait+0x34a/0x580 block/blk-wbt.c:659
 __rq_qos_throttle+0x65/0xb0 block/blk-rq-qos.c:66
 rq_qos_throttle block/blk-rq-qos.h:151 [inline]
 blk_mq_get_new_requests block/blk-mq.c:2955 [inline]
 blk_mq_submit_bio+0x8fb/0x2220 block/blk-mq.c:3056
 __submit_bio+0x12b/0x260 block/blk-core.c:610
 __submit_bio_noacct_mq block/blk-core.c:689 [inline]
 submit_bio_noacct_nocheck+0x6e8/0x9c0 block/blk-core.c:718
 ext4_io_submit fs/ext4/page-io.c:389 [inline]
 io_submit_add_bh fs/ext4/page-io.c:430 [inline]
 ext4_bio_write_folio+0x16a4/0x22d0 fs/ext4/page-io.c:578
 mpage_submit_folio+0x231/0x3c0 fs/ext4/inode.c:1911
 mpage_process_page_bufs+0x6bf/0x8c0 fs/ext4/inode.c:2024
 mpage_prepare_extent_to_map+0xecd/0x1f80 fs/ext4/inode.c:2544
 ext4_do_writepages+0xb46/0x3990 fs/ext4/inode.c:2686
 ext4_writepages+0x1dd/0x350 fs/ext4/inode.c:2822
 do_writepages+0x351/0x590 mm/page-writeback.c:2575
 __writeback_single_inode+0x14e/0xee0 fs/fs-writeback.c:1701
 writeback_sb_inodes+0x813/0x1020 fs/fs-writeback.c:1992
 __writeback_inodes_wb+0x114/0x240 fs/fs-writeback.c:2063
 wb_writeback+0x472/0xbe0 fs/fs-writeback.c:2173
 wb_check_background_flush fs/fs-writeback.c:2243 [inline]
 wb_do_writeback fs/fs-writeback.c:2331 [inline]
 wb_workfn+0xb8e/0xe60 fs/fs-writeback.c:2358
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
INFO: task jbd2/sda1-8:5103 blocked for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:jbd2/sda1-8     state:D stack:25384 pid:5103  ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 io_schedule+0x80/0xd0 kernel/sched/core.c:9024
 bit_wait_io+0x11/0xd0 kernel/sched/wait_bit.c:209
 __wait_on_bit+0x9f/0x2c0 kernel/sched/wait_bit.c:49
 out_of_line_wait_on_bit+0x13c/0x190 kernel/sched/wait_bit.c:64
 wait_on_buffer include/linux/buffer_head.h:373 [inline]
 jbd2_journal_commit_transaction+0x2e8d/0x5ad0 fs/jbd2/commit.c:815
 kjournald2+0x40f/0x810 fs/jbd2/journal.c:201
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
INFO: task syz-executor:5762 blocked for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:22888 pid:5762  ppid:5761   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 io_schedule+0x80/0xd0 kernel/sched/core.c:9024
 bit_wait_io+0x11/0xd0 kernel/sched/wait_bit.c:209
 __wait_on_bit+0x9f/0x2c0 kernel/sched/wait_bit.c:49
 out_of_line_wait_on_bit+0x13c/0x190 kernel/sched/wait_bit.c:64
 wait_on_bit_io include/linux/wait_bit.h:101 [inline]
 do_get_write_access+0x5c9/0xe00 fs/jbd2/transaction.c:1096
 jbd2_journal_get_write_access+0x10c/0x140 fs/jbd2/transaction.c:1231
 __ext4_journal_get_write_access+0x208/0x6d0 fs/ext4/ext4_jbd2.c:241
 ext4_reserve_inode_write+0x205/0x2a0 fs/ext4/inode.c:5945
 __ext4_mark_inode_dirty+0x13f/0x720 fs/ext4/inode.c:6129
 ext4_dirty_inode+0xcb/0x110 fs/ext4/inode.c:6166
 __mark_inode_dirty+0x2cc/0xc90 fs/fs-writeback.c:2537
 generic_update_time fs/inode.c:1981 [inline]
 inode_update_time fs/inode.c:1994 [inline]
 __file_update_time fs/inode.c:2180 [inline]
 file_update_time+0x187/0x1a0 fs/inode.c:2210
 ext4_page_mkwrite+0x1f9/0x11a0 fs/ext4/inode.c:6284
 do_page_mkwrite+0x153/0x3f0 mm/memory.c:2951
 wp_page_shared mm/memory.c:3311 [inline]
 do_wp_page+0xd4d/0x34d0 mm/memory.c:3396
 handle_pte_fault mm/memory.c:5063 [inline]
 __handle_mm_fault mm/memory.c:5188 [inline]
 handle_mm_fault+0x1306/0x4a50 mm/memory.c:5353
 do_user_addr_fault+0x736/0x12d0 arch/x86/mm/fault.c:1371
 handle_page_fault arch/x86/mm/fault.c:1463 [inline]
 exc_page_fault+0x64/0x100 arch/x86/mm/fault.c:1516
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0033:0x7fc52727cae2
RSP: 002b:00007fff8f257490 EFLAGS: 00010246
RAX: 00007fc52518c000 RBX: 000055557a61d1b0 RCX: 0000000000000000
RDX: 0000000000000295 RSI: 000055557a61f108 RDI: 0000000000000001
RBP: 00007fff8f257990 R08: 000055557a61f130 R09: 0000000000000091
R10: 0000000000000000 R11: 0000000000000202 R12: 00007fff8f2577d0
R13: 00007fff8f2575c0 R14: 585858582e7a7973 R15: 00007fff8f257510
 </TASK>
INFO: task syz.2.2232:11560 blocked for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.2232      state:D stack:27048 pid:11560 ppid:5774   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 io_schedule+0x80/0xd0 kernel/sched/core.c:9024
 bit_wait_io+0x11/0xd0 kernel/sched/wait_bit.c:209
 __wait_on_bit+0x9f/0x2c0 kernel/sched/wait_bit.c:49
 out_of_line_wait_on_bit+0x13c/0x190 kernel/sched/wait_bit.c:64
 wait_on_bit_io include/linux/wait_bit.h:101 [inline]
 do_get_write_access+0x5c9/0xe00 fs/jbd2/transaction.c:1096
 jbd2_journal_get_write_access+0x10c/0x140 fs/jbd2/transaction.c:1231
 __ext4_journal_get_write_access+0x208/0x6d0 fs/ext4/ext4_jbd2.c:241
 ext4_reserve_inode_write+0x205/0x2a0 fs/ext4/inode.c:5945
 __ext4_mark_inode_dirty+0x13f/0x720 fs/ext4/inode.c:6129
 ext4_dirty_inode+0xcb/0x110 fs/ext4/inode.c:6166
 __mark_inode_dirty+0x2cc/0xc90 fs/fs-writeback.c:2537
 generic_update_time fs/inode.c:1981 [inline]
 inode_update_time fs/inode.c:1994 [inline]
 __file_update_time fs/inode.c:2180 [inline]
 file_update_time+0x187/0x1a0 fs/inode.c:2210
 ext4_page_mkwrite+0x1f9/0x11a0 fs/ext4/inode.c:6284
 do_page_mkwrite+0x153/0x3f0 mm/memory.c:2951
 do_shared_fault mm/memory.c:4717 [inline]
 do_fault mm/memory.c:4779 [inline]
 do_pte_missing mm/memory.c:3689 [inline]
 handle_pte_fault mm/memory.c:5047 [inline]
 __handle_mm_fault mm/memory.c:5188 [inline]
 handle_mm_fault+0x1a2c/0x4a50 mm/memory.c:5353
 do_user_addr_fault+0x736/0x12d0 arch/x86/mm/fault.c:1371
 handle_page_fault arch/x86/mm/fault.c:1463 [inline]
 exc_page_fault+0x64/0x100 arch/x86/mm/fault.c:1516
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0033:0x7f2239e73332
RSP: 002b:00007ffff51ccd30 EFLAGS: 00010202
RAX: 0000000000004008 RBX: 00007f223ad55720 RCX: 0000000000000000
RDX: 0000001b2de20000 RSI: 0000000000000008 RDI: 00007f223ad55720
RBP: 0000000000000142 R08: 00007f223a210000 R09: 00007f223a226038
R10: 0000000000000003 R11: 0000000000000001 R12: ffffffff818b16bc
R13: 00007f223a226038 R14: 00000000000000d4 R15: ffffffffffffc000
 </TASK>
INFO: task syz.0.2241:11580 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.2241      state:D stack:27048 pid:11580 ppid:5777   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 io_schedule+0x80/0xd0 kernel/sched/core.c:9024
 bit_wait_io+0x11/0xd0 kernel/sched/wait_bit.c:209
 __wait_on_bit+0x9f/0x2c0 kernel/sched/wait_bit.c:49
 out_of_line_wait_on_bit+0x13c/0x190 kernel/sched/wait_bit.c:64
 wait_on_bit_io include/linux/wait_bit.h:101 [inline]
 do_get_write_access+0x5c9/0xe00 fs/jbd2/transaction.c:1096
 jbd2_journal_get_write_access+0x10c/0x140 fs/jbd2/transaction.c:1231
 __ext4_journal_get_write_access+0x208/0x6d0 fs/ext4/ext4_jbd2.c:241
 ext4_reserve_inode_write+0x205/0x2a0 fs/ext4/inode.c:5945
 __ext4_mark_inode_dirty+0x13f/0x720 fs/ext4/inode.c:6129
 ext4_dirty_inode+0xcb/0x110 fs/ext4/inode.c:6166
 __mark_inode_dirty+0x2cc/0xc90 fs/fs-writeback.c:2537
 generic_update_time fs/inode.c:1981 [inline]
 inode_update_time fs/inode.c:1994 [inline]
 __file_update_time fs/inode.c:2180 [inline]
 file_update_time+0x187/0x1a0 fs/inode.c:2210
 ext4_page_mkwrite+0x1f9/0x11a0 fs/ext4/inode.c:6284
 do_page_mkwrite+0x153/0x3f0 mm/memory.c:2951
 do_shared_fault mm/memory.c:4717 [inline]
 do_fault mm/memory.c:4779 [inline]
 do_pte_missing mm/memory.c:3689 [inline]
 handle_pte_fault mm/memory.c:5047 [inline]
 __handle_mm_fault mm/memory.c:5188 [inline]
 handle_mm_fault+0x1a2c/0x4a50 mm/memory.c:5353
 do_user_addr_fault+0x736/0x12d0 arch/x86/mm/fault.c:1371
 handle_page_fault arch/x86/mm/fault.c:1463 [inline]
 exc_page_fault+0x64/0x100 arch/x86/mm/fault.c:1516
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0033:0x7f8733073332
RSP: 002b:00007ffc81fd8360 EFLAGS: 00010202
RAX: 0000000000008008 RBX: 00007f8733f55720 RCX: 0000000000000000
RDX: 0000001b2dc1c000 RSI: 0000000000000008 RDI: 00007f8733f55720
RBP: 00000000000004f8 R08: 00007f8733410000 R09: 00007f8733426038
R10: 0000000000000003 R11: 0000000000000002 R12: ffffffff81f2a7c4
R13: 00007f8733426038 R14: 00000000000001a4 R15: ffffffffffff8000
 </TASK>
INFO: task syz.3.2240:11581 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.2240      state:D stack:27048 pid:11581 ppid:5776   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 io_schedule+0x80/0xd0 kernel/sched/core.c:9024
 bit_wait_io+0x11/0xd0 kernel/sched/wait_bit.c:209
 __wait_on_bit+0x9f/0x2c0 kernel/sched/wait_bit.c:49
 out_of_line_wait_on_bit+0x13c/0x190 kernel/sched/wait_bit.c:64
 wait_on_bit_io include/linux/wait_bit.h:101 [inline]
 do_get_write_access+0x5c9/0xe00 fs/jbd2/transaction.c:1096
 jbd2_journal_get_write_access+0x10c/0x140 fs/jbd2/transaction.c:1231
 __ext4_journal_get_write_access+0x208/0x6d0 fs/ext4/ext4_jbd2.c:241
 ext4_reserve_inode_write+0x205/0x2a0 fs/ext4/inode.c:5945
 __ext4_mark_inode_dirty+0x13f/0x720 fs/ext4/inode.c:6129
 ext4_dirty_inode+0xcb/0x110 fs/ext4/inode.c:6166
 __mark_inode_dirty+0x2cc/0xc90 fs/fs-writeback.c:2537
 generic_update_time fs/inode.c:1981 [inline]
 inode_update_time fs/inode.c:1994 [inline]
 __file_update_time fs/inode.c:2180 [inline]
 file_update_time+0x187/0x1a0 fs/inode.c:2210
 ext4_page_mkwrite+0x1f9/0x11a0 fs/ext4/inode.c:6284
 do_page_mkwrite+0x153/0x3f0 mm/memory.c:2951
 do_shared_fault mm/memory.c:4717 [inline]
 do_fault mm/memory.c:4779 [inline]
 do_pte_missing mm/memory.c:3689 [inline]
 handle_pte_fault mm/memory.c:5047 [inline]
 __handle_mm_fault mm/memory.c:5188 [inline]
 handle_mm_fault+0x1a2c/0x4a50 mm/memory.c:5353
 do_user_addr_fault+0x736/0x12d0 arch/x86/mm/fault.c:1371
 handle_page_fault arch/x86/mm/fault.c:1463 [inline]
 exc_page_fault+0x64/0x100 arch/x86/mm/fault.c:1516
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0033:0x7f97c1a72c09
RSP: 002b:00007ffc2a80b440 EFLAGS: 00010202
RAX: 0000001b2df24000 RBX: 0000000000000000 RCX: 00000000005ffde8
RDX: 0000001b2df23ffc RSI: 00000000005ffde8 RDI: 00007f97c2955700
RBP: 0000000000000000 R08: 0000000000000000 R09: 00007f97c1e12000
R10: 00007f97c2955700 R11: 0000000000000000 R12: 0000000000000000
R13: 00000000000027ad R14: ffffffff81322060 R15: 00007f97c2955720
 </TASK>
INFO: task syz.1.2242:11585 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.2242      state:D stack:27560 pid:11585 ppid:5775   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 io_schedule+0x80/0xd0 kernel/sched/core.c:9024
 bit_wait_io+0x11/0xd0 kernel/sched/wait_bit.c:209
 __wait_on_bit+0x9f/0x2c0 kernel/sched/wait_bit.c:49
 out_of_line_wait_on_bit+0x13c/0x190 kernel/sched/wait_bit.c:64
 wait_on_bit_io include/linux/wait_bit.h:101 [inline]
 do_get_write_access+0x5c9/0xe00 fs/jbd2/transaction.c:1096
 jbd2_journal_get_write_access+0x10c/0x140 fs/jbd2/transaction.c:1231
 __ext4_journal_get_write_access+0x208/0x6d0 fs/ext4/ext4_jbd2.c:241
 ext4_reserve_inode_write+0x205/0x2a0 fs/ext4/inode.c:5945
 __ext4_mark_inode_dirty+0x13f/0x720 fs/ext4/inode.c:6129
 ext4_dirty_inode+0xcb/0x110 fs/ext4/inode.c:6166
 __mark_inode_dirty+0x2cc/0xc90 fs/fs-writeback.c:2537
 generic_update_time fs/inode.c:1981 [inline]
 inode_update_time fs/inode.c:1994 [inline]
 __file_update_time fs/inode.c:2180 [inline]
 file_update_time+0x187/0x1a0 fs/inode.c:2210
 ext4_page_mkwrite+0x1f9/0x11a0 fs/ext4/inode.c:6284
 do_page_mkwrite+0x153/0x3f0 mm/memory.c:2951
 do_shared_fault mm/memory.c:4717 [inline]
 do_fault mm/memory.c:4779 [inline]
 do_pte_missing mm/memory.c:3689 [inline]
 handle_pte_fault mm/memory.c:5047 [inline]
 __handle_mm_fault mm/memory.c:5188 [inline]
 handle_mm_fault+0x1a2c/0x4a50 mm/memory.c:5353
 do_user_addr_fault+0x736/0x12d0 arch/x86/mm/fault.c:1371
 handle_page_fault arch/x86/mm/fault.c:1463 [inline]
 exc_page_fault+0x64/0x100 arch/x86/mm/fault.c:1516
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0033:0x7f2476e6bea3
RSP: 002b:00007ffdfb10d180 EFLAGS: 00010246
RAX: 00000000005ffde8 RBX: 0000000000000000 RCX: 0000001b2d764000
RDX: 0000001b2d724000 RSI: 0000000000600000 RDI: 00007f24771e3708
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 00007ffdfb10d410
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
 #0: ffffffff8df320e0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #0: ffffffff8df320e0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #0: ffffffff8df320e0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6669
1 lock held by khugepaged/35:
 #0: ffff88807dd6a7a0 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock include/linux/mmap_lock.h:108 [inline]
 #0: ffff88807dd6a7a0 (&mm->mmap_lock){++++}-{3:3}, at: collapse_huge_page mm/khugepaged.c:1133 [inline]
 #0: ffff88807dd6a7a0 (&mm->mmap_lock){++++}-{3:3}, at: hpage_collapse_scan_pmd+0x216a/0x4050 mm/khugepaged.c:1393
4 locks held by kworker/u4:4/59:
 #0: ffff88801da6b138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #0: ffff88801da6b138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #1: ffffc900015a7d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #1: ffffc900015a7d00 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #2: ffff88814d9160e0 (&type->s_umount_key#31){++++}-{3:3}, at: super_trylock_shared+0x20/0xf0 fs/super.c:607
 #3: ffff88814d918c58 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_read fs/ext4/ext4.h:1768 [inline]
 #3: ffff88814d918c58 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages+0x1a4/0x350 fs/ext4/inode.c:2821
2 locks held by getty/5527:
 #0: ffff88803308a0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc900032932f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x428/0x1370 drivers/tty/n_tty.c:2217
3 locks held by syz-executor/5762:
 #0: ffff88807f955720 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:165 [inline]
 #0: ffff88807f955720 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5380 [inline]
 #0: ffff88807f955720 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x32/0x2f0 mm/memory.c:5440
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: __sb_start_write include/linux/fs.h:1633 [inline]
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: sb_start_pagefault include/linux/fs.h:1737 [inline]
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: ext4_page_mkwrite+0x1e2/0x11a0 fs/ext4/inode.c:6283
 #2: ffff88814d91a990 (jbd2_handle){++++}-{0:0}, at: start_this_handle+0x1f3f/0x2170 fs/jbd2/transaction.c:448
3 locks held by syz.2.2232/11560:
 #0: ffff88807dd6a7a0 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:165 [inline]
 #0: ffff88807dd6a7a0 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5380 [inline]
 #0: ffff88807dd6a7a0 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x32/0x2f0 mm/memory.c:5440
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: __sb_start_write include/linux/fs.h:1633 [inline]
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: sb_start_pagefault include/linux/fs.h:1737 [inline]
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: ext4_page_mkwrite+0x1e2/0x11a0 fs/ext4/inode.c:6283
 #2: ffff88814d91a990 (jbd2_handle){++++}-{0:0}, at: start_this_handle+0x1f3f/0x2170 fs/jbd2/transaction.c:448
3 locks held by syz.0.2241/11580:
 #0: ffff8880782c4420 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:165 [inline]
 #0: ffff8880782c4420 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5380 [inline]
 #0: ffff8880782c4420 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x32/0x2f0 mm/memory.c:5440
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: __sb_start_write include/linux/fs.h:1633 [inline]
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: sb_start_pagefault include/linux/fs.h:1737 [inline]
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: ext4_page_mkwrite+0x1e2/0x11a0 fs/ext4/inode.c:6283
 #2: ffff88814d91a990 (jbd2_handle){++++}-{0:0}, at: start_this_handle+0x1f3f/0x2170 fs/jbd2/transaction.c:448
3 locks held by syz.3.2240/11581:
 #0: ffff888026463aa0 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:165 [inline]
 #0: ffff888026463aa0 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5380 [inline]
 #0: ffff888026463aa0 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x32/0x2f0 mm/memory.c:5440
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: __sb_start_write include/linux/fs.h:1633 [inline]
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: sb_start_pagefault include/linux/fs.h:1737 [inline]
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: ext4_page_mkwrite+0x1e2/0x11a0 fs/ext4/inode.c:6283
 #2: ffff88814d91a990 (jbd2_handle){++++}-{0:0}, at: start_this_handle+0x1f3f/0x2170 fs/jbd2/transaction.c:448
3 locks held by syz.1.2242/11585:
 #0: ffff8880330b3120 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:165 [inline]
 #0: ffff8880330b3120 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5380 [inline]
 #0: ffff8880330b3120 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x32/0x2f0 mm/memory.c:5440
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: __sb_start_write include/linux/fs.h:1633 [inline]
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: sb_start_pagefault include/linux/fs.h:1737 [inline]
 #1: ffff88814d916510 (sb_pagefaults){.+.+}-{0:0}, at: ext4_page_mkwrite+0x1e2/0x11a0 fs/ext4/inode.c:6283
 #2: ffff88814d91a990 (jbd2_handle){++++}-{0:0}, at: start_this_handle+0x1f3f/0x2170 fs/jbd2/transaction.c:448

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 29 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a6/0x3e0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x2f0 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
 watchdog+0xf59/0xfa0 kernel/hung_task.c:379
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 2929 Comm: kworker/u4:7 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Workqueue: events_unbound nsim_dev_trap_report_work
RIP: 0010:clear_page_erms+0xb/0x10 arch/x86/lib/clear_page_64.S:50
Code: 48 89 47 20 48 89 47 28 48 89 47 30 48 89 47 38 48 8d 7f 40 75 d9 90 c3 90 90 90 90 90 90 90 f3 0f 1e fa b9 00 10 00 00 31 c0 <f3> aa c3 90 90 f3 0f 1e fa 48 83 f9 40 73 36 83 f9 08 73 0f 85 c9
RSP: 0018:ffffc9000bc8f5c8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000340
RDX: ffff8880787b1000 RSI: 0000000000000007 RDI: ffff8880787b1cc0
RBP: ffff88813fffc310 R08: ffffea0001e1ec37 R09: 0000000000000000
R10: ffffed100f0f6000 R11: fffff940003c3d87 R12: 0000000000000000
R13: 0000000000000001 R14: ffffea0001e1ec00 R15: 0000000000000008
FS:  0000000000000000(0000) GS:ffff8880b8d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005558af088660 CR3: 000000000dd32000 CR4: 00000000003526e0
Call Trace:
 <TASK>
 clear_page arch/x86/include/asm/page_64.h:54 [inline]
 clear_highpage_kasan_tagged include/linux/highmem.h:248 [inline]
 kernel_init_pages mm/page_alloc.c:1101 [inline]
 post_alloc_hook+0xf3/0x200 mm/page_alloc.c:1580
 prep_new_page mm/page_alloc.c:1589 [inline]
 get_page_from_freelist+0x2181/0x22a0 mm/page_alloc.c:3221
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4501
 alloc_slab_page+0x5d/0x180 mm/slub.c:1881
 allocate_slab mm/slub.c:2028 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2081
 ___slab_alloc+0xc5c/0x12f0 mm/slub.c:3253
 __slab_alloc mm/slub.c:3339 [inline]
 __slab_alloc_node mm/slub.c:3392 [inline]
 slab_alloc_node mm/slub.c:3485 [inline]
 __kmem_cache_alloc_node+0x11f/0x250 mm/slub.c:3534
 __do_kmalloc_node mm/slab_common.c:1006 [inline]
 __kmalloc_node_track_caller+0xa4/0x230 mm/slab_common.c:1027
 kmalloc_reserve+0x116/0x240 net/core/skbuff.c:584
 __alloc_skb+0x138/0x2c0 net/core/skbuff.c:653
 alloc_skb include/linux/skbuff.h:1316 [inline]
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:748 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:805 [inline]
 nsim_dev_trap_report_work+0x253/0xa90 drivers/net/netdevsim/dev.c:851
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/16 13:37 linux-6.6.y cecd39af8a1a 4c840a2f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in hpage_collapse_scan_pmd
2026/10/16 13:24 linux-6.6.y cecd39af8a1a 4c840a2f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in hpage_collapse_scan_pmd
2026/10/15 03:23 linux-6.6.y a91a6aa9253c 8fb0ae89 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in hpage_collapse_scan_pmd
2026/10/02 03:42 linux-6.6.y 79643295eba1 6d32eb1f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in hpage_collapse_scan_pmd
2026/08/23 05:16 linux-6.6.y c610b395b0a5 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in hpage_collapse_scan_pmd
* Struck through repros no longer work on HEAD.