* [syzbot] [mm?] INFO: task hung in __rmap_walk_file
@ 2025-10-10 20:49 syzbot
2025-10-11 3:11 ` Lance Yang
0 siblings, 1 reply; 4+ messages in thread
From: syzbot @ 2025-10-10 20:49 UTC (permalink / raw)
To: Liam.Howlett, akpm, david, harry.yoo, jannh, linux-kernel,
linux-mm, lorenzo.stoakes, riel, syzkaller-bugs, vbabka
Hello,
syzbot found the following issue on:
HEAD commit: 5472d60c129f Merge tag 'trace-v6.18-2' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16d69304580000
kernel config: https://syzkaller.appspot.com/x/.config?x=5b213914b883d014
dashboard link: https://syzkaller.appspot.com/bug?extid=2d9c96466c978346b55f
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=133e89e2580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17f3ba7c580000
Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-5472d60c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/af61e8db8b22/vmlinux-5472d60c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a2c11e401d8a/bzImage-5472d60c.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2d9c96466c978346b55f@syzkaller.appspotmail.com
INFO: task syz.5.48:5749 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.5.48 state:D stack:27656 pid:5749 tgid:5747 ppid:5477 task_flags:0x400040 flags:0x00080002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5325 [inline]
__schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
__schedule_loop kernel/sched/core.c:7011 [inline]
schedule+0x165/0x360 kernel/sched/core.c:7026
schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7083
rwsem_down_read_slowpath+0x5fd/0x8f0 kernel/locking/rwsem.c:1086
__down_read_common kernel/locking/rwsem.c:1261 [inline]
__down_read kernel/locking/rwsem.c:1274 [inline]
down_read+0x98/0x2e0 kernel/locking/rwsem.c:1539
i_mmap_lock_read include/linux/fs.h:568 [inline]
__rmap_walk_file+0x227/0x620 mm/rmap.c:2905
remove_migration_ptes mm/migrate.c:471 [inline]
unmap_and_move_huge_page mm/migrate.c:1520 [inline]
migrate_hugetlbs mm/migrate.c:1641 [inline]
migrate_pages+0xc98/0x2930 mm/migrate.c:2080
do_mbind mm/mempolicy.c:1539 [inline]
kernel_mbind mm/mempolicy.c:1682 [inline]
__do_sys_mbind mm/mempolicy.c:1756 [inline]
__se_sys_mbind+0xa47/0xc40 mm/mempolicy.c:1752
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd36cd8eec9
RSP: 002b:00007fd36dccd038 EFLAGS: 00000246 ORIG_RAX: 00000000000000ed
RAX: ffffffffffffffda RBX: 00007fd36cfe5fa0 RCX: 00007fd36cd8eec9
RDX: 0000000000000000 RSI: 0000000000800000 RDI: 0000200000001000
RBP: 00007fd36ce11f91 R08: 0000000000000040 R09: 0000000000000002
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd36cfe6038 R14: 00007fd36cfe5fa0 R15: 00007ffec3386808
</TASK>
INFO: task syz.5.48:5754 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.5.48 state:D stack:26920 pid:5754 tgid:5747 ppid:5477 task_flags:0x400040 flags:0x00080002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5325 [inline]
__schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
__schedule_loop kernel/sched/core.c:7011 [inline]
schedule+0x165/0x360 kernel/sched/core.c:7026
io_schedule+0x80/0xd0 kernel/sched/core.c:7871
folio_wait_bit_common+0x6b0/0xb80 mm/filemap.c:1330
__folio_lock mm/filemap.c:1706 [inline]
folio_lock include/linux/pagemap.h:1141 [inline]
__filemap_get_folio+0x139/0xaf0 mm/filemap.c:1960
filemap_lock_folio include/linux/pagemap.h:820 [inline]
filemap_lock_hugetlb_folio include/linux/hugetlb.h:814 [inline]
hugetlbfs_zero_partial_page+0xae/0x610 fs/hugetlbfs/inode.c:654
hugetlbfs_punch_hole fs/hugetlbfs/inode.c:708 [inline]
hugetlbfs_fallocate+0xb91/0x1100 fs/hugetlbfs/inode.c:741
vfs_fallocate+0x666/0x7e0 fs/open.c:342
madvise_remove mm/madvise.c:1049 [inline]
madvise_vma_behavior+0x31b3/0x3a10 mm/madvise.c:1346
madvise_walk_vmas+0x51c/0xa30 mm/madvise.c:1669
madvise_do_behavior+0x38e/0x550 mm/madvise.c:1885
do_madvise+0x1bc/0x270 mm/madvise.c:1978
__do_sys_madvise mm/madvise.c:1987 [inline]
__se_sys_madvise mm/madvise.c:1985 [inline]
__x64_sys_madvise+0xa7/0xc0 mm/madvise.c:1985
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd36cd8eec9
RSP: 002b:00007fd36dcac038 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 00007fd36cfe6090 RCX: 00007fd36cd8eec9
RDX: 0000000000000009 RSI: 0000000000600002 RDI: 0000200000000000
RBP: 00007fd36ce11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd36cfe6128 R14: 00007fd36cfe6090 R15: 00007ffec3386808
</TASK>
Showing all locks held in the system:
3 locks held by kworker/u4:0/12:
#0: ffff88801a479948 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3238 [inline]
#0: ffff88801a479948 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3346
#1: ffffc900001e7ba0 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3239 [inline]
#1: ffffc900001e7ba0 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3346
#2: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:303
1 lock held by khungtaskd/26:
#0: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
#0: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
#0: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
5 locks held by kworker/u4:6/1041:
#0: ffff88801b6f8948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3238 [inline]
#0: ffff88801b6f8948 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3346
#1: ffffc900025b7ba0 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3239 [inline]
#1: ffffc900025b7ba0 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3346
#2: ffffffff8f4d4c50 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xf7/0x820 net/core/net_namespace.c:669
#3: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: default_device_exit_batch+0xdc/0x890 net/core/dev.c:12807
#4: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:311 [inline]
#4: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x2f6/0x730 kernel/rcu/tree_exp.h:957
1 lock held by dhcpcd/5017:
#0: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
#0: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: devinet_ioctl+0x323/0x1b50 net/ipv4/devinet.c:1120
2 locks held by getty/5110:
#0: ffff88803597c0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000018e2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400 drivers/tty/n_tty.c:2222
1 lock held by syz.5.48/5749:
#0: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: i_mmap_lock_read include/linux/fs.h:568 [inline]
#0: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: __rmap_walk_file+0x227/0x620 mm/rmap.c:2905
3 locks held by syz.5.48/5754:
#0: ffff88801ebe2420 (sb_writers#12){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3111 [inline]
#0: ffff88801ebe2420 (sb_writers#12){.+.+}-{0:0}, at: vfs_fallocate+0x5f0/0x7e0 fs/open.c:341
#1: ffff888011d3f348 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:980 [inline]
#1: ffff888011d3f348 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: hugetlbfs_punch_hole fs/hugetlbfs/inode.c:683 [inline]
#1: ffff888011d3f348 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: hugetlbfs_fallocate+0x3cc/0x1100 fs/hugetlbfs/inode.c:741
#2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: i_mmap_lock_write include/linux/fs.h:548 [inline]
#2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: hugetlbfs_punch_hole fs/hugetlbfs/inode.c:691 [inline]
#2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: hugetlbfs_fallocate+0x4b5/0x1100 fs/hugetlbfs/inode.c:741
2 locks held by syz-executor/20402:
#0: ffffffff8ec74400 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
#0: ffffffff8ec74400 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
#0: ffffffff8ec74400 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x23/0x250 net/core/rtnetlink.c:570
#1: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
#1: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
#1: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x8e9/0x1c80 net/core/rtnetlink.c:4064
1 lock held by syz.4.7446/21125:
#0: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:343 [inline]
#0: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x3b9/0x730 kernel/rcu/tree_exp.h:957
=============================================
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 26 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
nmi_cpu_backtrace+0x39e/0x3d0 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:332 [inline]
watchdog+0xf60/0xfa0 kernel/hung_task.c:495
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
---
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syzbot will keep track of this issue. See:
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If the report is already addressed, let syzbot know by replying with:
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [syzbot] [mm?] INFO: task hung in __rmap_walk_file
2025-10-10 20:49 [syzbot] [mm?] INFO: task hung in __rmap_walk_file syzbot
@ 2025-10-11 3:11 ` Lance Yang
2025-10-11 6:10 ` Lance Yang
0 siblings, 1 reply; 4+ messages in thread
From: Lance Yang @ 2025-10-11 3:11 UTC (permalink / raw)
To: syzbot
Cc: Liam.Howlett, akpm, david, harry.yoo, jannh, linux-kernel,
linux-mm, lorenzo.stoakes, riel, syzkaller-bugs, vbabka
On Sat, Oct 11, 2025 at 4:49 AM syzbot
<syzbot+2d9c96466c978346b55f@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 5472d60c129f Merge tag 'trace-v6.18-2' of git://git.kernel..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16d69304580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=5b213914b883d014
> dashboard link: https://syzkaller.appspot.com/bug?extid=2d9c96466c978346b55f
> compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=133e89e2580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17f3ba7c580000
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-5472d60c.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/af61e8db8b22/vmlinux-5472d60c.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/a2c11e401d8a/bzImage-5472d60c.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+2d9c96466c978346b55f@syzkaller.appspotmail.com
>
> INFO: task syz.5.48:5749 blocked for more than 143 seconds.
> Not tainted syzkaller #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz.5.48 state:D stack:27656 pid:5749 tgid:5747 ppid:5477 task_flags:0x400040 flags:0x00080002
> Call Trace:
> <TASK>
> context_switch kernel/sched/core.c:5325 [inline]
> __schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
> __schedule_loop kernel/sched/core.c:7011 [inline]
> schedule+0x165/0x360 kernel/sched/core.c:7026
> schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7083
> rwsem_down_read_slowpath+0x5fd/0x8f0 kernel/locking/rwsem.c:1086
It would be great if CONFIG_DETECT_HUNG_TASK_BLOCKER was set, as it could
point directly to the blocker. However, the lockdep output at the end of
the report already gives us the crucial clue :)
```
1 lock held by syz.5.48/5749:
#0: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
i_mmap_lock_read include/linux/fs.h:568 [inline]
#0: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
__rmap_walk_file+0x227/0x620 mm/rmap.c:2905
3 locks held by syz.5.48/5754:
...
#2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
i_mmap_lock_write include/linux/fs.h:548 [inline]
#2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
hugetlbfs_punch_hole fs/hugetlbfs/inode.c:691 [inline]
#2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
hugetlbfs_fallocate+0x4b5/0x1100
```
1) One task (5754) holds the i_mmap_rwsem write lock for hugetlbfs_fallocate.
2) While holding that lock, it blocks waiting for a folio_lock (according
to its call trace).
3) This starves the other task (5749), which is waiting for the i_mmap_rwsem
read lock to perform migrate_pages.
From the report, I cannot tell who originally held the folio_lock that
blocked task 5754. I hope this analysis is useful ...
Thanks,
Lance
> __down_read_common kernel/locking/rwsem.c:1261 [inline]
> __down_read kernel/locking/rwsem.c:1274 [inline]
> down_read+0x98/0x2e0 kernel/locking/rwsem.c:1539
> i_mmap_lock_read include/linux/fs.h:568 [inline]
> __rmap_walk_file+0x227/0x620 mm/rmap.c:2905
> remove_migration_ptes mm/migrate.c:471 [inline]
> unmap_and_move_huge_page mm/migrate.c:1520 [inline]
> migrate_hugetlbs mm/migrate.c:1641 [inline]
> migrate_pages+0xc98/0x2930 mm/migrate.c:2080
> do_mbind mm/mempolicy.c:1539 [inline]
> kernel_mbind mm/mempolicy.c:1682 [inline]
> __do_sys_mbind mm/mempolicy.c:1756 [inline]
> __se_sys_mbind+0xa47/0xc40 mm/mempolicy.c:1752
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fd36cd8eec9
> RSP: 002b:00007fd36dccd038 EFLAGS: 00000246 ORIG_RAX: 00000000000000ed
> RAX: ffffffffffffffda RBX: 00007fd36cfe5fa0 RCX: 00007fd36cd8eec9
> RDX: 0000000000000000 RSI: 0000000000800000 RDI: 0000200000001000
> RBP: 00007fd36ce11f91 R08: 0000000000000040 R09: 0000000000000002
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fd36cfe6038 R14: 00007fd36cfe5fa0 R15: 00007ffec3386808
> </TASK>
> INFO: task syz.5.48:5754 blocked for more than 143 seconds.
> Not tainted syzkaller #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz.5.48 state:D stack:26920 pid:5754 tgid:5747 ppid:5477 task_flags:0x400040 flags:0x00080002
> Call Trace:
> <TASK>
> context_switch kernel/sched/core.c:5325 [inline]
> __schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
> __schedule_loop kernel/sched/core.c:7011 [inline]
> schedule+0x165/0x360 kernel/sched/core.c:7026
> io_schedule+0x80/0xd0 kernel/sched/core.c:7871
> folio_wait_bit_common+0x6b0/0xb80 mm/filemap.c:1330
> __folio_lock mm/filemap.c:1706 [inline]
> folio_lock include/linux/pagemap.h:1141 [inline]
> __filemap_get_folio+0x139/0xaf0 mm/filemap.c:1960
> filemap_lock_folio include/linux/pagemap.h:820 [inline]
> filemap_lock_hugetlb_folio include/linux/hugetlb.h:814 [inline]
> hugetlbfs_zero_partial_page+0xae/0x610 fs/hugetlbfs/inode.c:654
> hugetlbfs_punch_hole fs/hugetlbfs/inode.c:708 [inline]
> hugetlbfs_fallocate+0xb91/0x1100 fs/hugetlbfs/inode.c:741
> vfs_fallocate+0x666/0x7e0 fs/open.c:342
> madvise_remove mm/madvise.c:1049 [inline]
> madvise_vma_behavior+0x31b3/0x3a10 mm/madvise.c:1346
> madvise_walk_vmas+0x51c/0xa30 mm/madvise.c:1669
> madvise_do_behavior+0x38e/0x550 mm/madvise.c:1885
> do_madvise+0x1bc/0x270 mm/madvise.c:1978
> __do_sys_madvise mm/madvise.c:1987 [inline]
> __se_sys_madvise mm/madvise.c:1985 [inline]
> __x64_sys_madvise+0xa7/0xc0 mm/madvise.c:1985
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fd36cd8eec9
> RSP: 002b:00007fd36dcac038 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
> RAX: ffffffffffffffda RBX: 00007fd36cfe6090 RCX: 00007fd36cd8eec9
> RDX: 0000000000000009 RSI: 0000000000600002 RDI: 0000200000000000
> RBP: 00007fd36ce11f91 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fd36cfe6128 R14: 00007fd36cfe6090 R15: 00007ffec3386808
> </TASK>
>
> Showing all locks held in the system:
> 3 locks held by kworker/u4:0/12:
> #0: ffff88801a479948 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3238 [inline]
> #0: ffff88801a479948 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3346
> #1: ffffc900001e7ba0 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3239 [inline]
> #1: ffffc900001e7ba0 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3346
> #2: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:303
> 1 lock held by khungtaskd/26:
> #0: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
> #0: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
> #0: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
> 5 locks held by kworker/u4:6/1041:
> #0: ffff88801b6f8948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3238 [inline]
> #0: ffff88801b6f8948 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3346
> #1: ffffc900025b7ba0 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3239 [inline]
> #1: ffffc900025b7ba0 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3346
> #2: ffffffff8f4d4c50 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xf7/0x820 net/core/net_namespace.c:669
> #3: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: default_device_exit_batch+0xdc/0x890 net/core/dev.c:12807
> #4: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:311 [inline]
> #4: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x2f6/0x730 kernel/rcu/tree_exp.h:957
> 1 lock held by dhcpcd/5017:
> #0: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
> #0: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: devinet_ioctl+0x323/0x1b50 net/ipv4/devinet.c:1120
> 2 locks held by getty/5110:
> #0: ffff88803597c0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
> #1: ffffc9000018e2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400 drivers/tty/n_tty.c:2222
> 1 lock held by syz.5.48/5749:
> #0: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: i_mmap_lock_read include/linux/fs.h:568 [inline]
> #0: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: __rmap_walk_file+0x227/0x620 mm/rmap.c:2905
> 3 locks held by syz.5.48/5754:
> #0: ffff88801ebe2420 (sb_writers#12){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3111 [inline]
> #0: ffff88801ebe2420 (sb_writers#12){.+.+}-{0:0}, at: vfs_fallocate+0x5f0/0x7e0 fs/open.c:341
> #1: ffff888011d3f348 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:980 [inline]
> #1: ffff888011d3f348 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: hugetlbfs_punch_hole fs/hugetlbfs/inode.c:683 [inline]
> #1: ffff888011d3f348 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: hugetlbfs_fallocate+0x3cc/0x1100 fs/hugetlbfs/inode.c:741
> #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: i_mmap_lock_write include/linux/fs.h:548 [inline]
> #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: hugetlbfs_punch_hole fs/hugetlbfs/inode.c:691 [inline]
> #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: hugetlbfs_fallocate+0x4b5/0x1100 fs/hugetlbfs/inode.c:741
> 2 locks held by syz-executor/20402:
> #0: ffffffff8ec74400 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
> #0: ffffffff8ec74400 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
> #0: ffffffff8ec74400 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x23/0x250 net/core/rtnetlink.c:570
> #1: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
> #1: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
> #1: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x8e9/0x1c80 net/core/rtnetlink.c:4064
> 1 lock held by syz.4.7446/21125:
> #0: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:343 [inline]
> #0: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x3b9/0x730 kernel/rcu/tree_exp.h:957
>
> =============================================
>
> NMI backtrace for cpu 0
> CPU: 0 UID: 0 PID: 26 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> Call Trace:
> <TASK>
> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
> nmi_cpu_backtrace+0x39e/0x3d0 lib/nmi_backtrace.c:113
> nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
> trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
> check_hung_uninterruptible_tasks kernel/hung_task.c:332 [inline]
> watchdog+0xf60/0xfa0 kernel/hung_task.c:495
> kthread+0x711/0x8a0 kernel/kthread.c:463
> ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> </TASK>
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
>
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> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
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>
> If you want to undo deduplication, reply with:
> #syz undup
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [syzbot] [mm?] INFO: task hung in __rmap_walk_file
2025-10-11 3:11 ` Lance Yang
@ 2025-10-11 6:10 ` Lance Yang
2025-10-13 11:23 ` Harry Yoo
0 siblings, 1 reply; 4+ messages in thread
From: Lance Yang @ 2025-10-11 6:10 UTC (permalink / raw)
To: syzbot
Cc: Liam.Howlett, akpm, david, harry.yoo, jannh, linux-kernel,
linux-mm, lorenzo.stoakes, riel, syzkaller-bugs, vbabka,
Lance Yang
On Sat, Oct 11, 2025 at 11:11 AM Lance Yang <lance.yang@linux.dev> wrote:
>
> On Sat, Oct 11, 2025 at 4:49 AM syzbot
> <syzbot+2d9c96466c978346b55f@syzkaller.appspotmail.com> wrote:
> >
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: 5472d60c129f Merge tag 'trace-v6.18-2' of git://git.kernel..
> > git tree: upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=16d69304580000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=5b213914b883d014
> > dashboard link: https://syzkaller.appspot.com/bug?extid=2d9c96466c978346b55f
> > compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=133e89e2580000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17f3ba7c580000
> >
> > Downloadable assets:
> > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-5472d60c.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/af61e8db8b22/vmlinux-5472d60c.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/a2c11e401d8a/bzImage-5472d60c.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+2d9c96466c978346b55f@syzkaller.appspotmail.com
> >
> > INFO: task syz.5.48:5749 blocked for more than 143 seconds.
> > Not tainted syzkaller #0
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > task:syz.5.48 state:D stack:27656 pid:5749 tgid:5747 ppid:5477 task_flags:0x400040 flags:0x00080002
> > Call Trace:
> > <TASK>
> > context_switch kernel/sched/core.c:5325 [inline]
> > __schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
> > __schedule_loop kernel/sched/core.c:7011 [inline]
> > schedule+0x165/0x360 kernel/sched/core.c:7026
> > schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7083
> > rwsem_down_read_slowpath+0x5fd/0x8f0 kernel/locking/rwsem.c:1086
>
> It would be great if CONFIG_DETECT_HUNG_TASK_BLOCKER was set, as it could
> point directly to the blocker. However, the lockdep output at the end of
> the report already gives us the crucial clue :)
>
> ```
> 1 lock held by syz.5.48/5749:
> #0: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
> i_mmap_lock_read include/linux/fs.h:568 [inline]
> #0: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
> __rmap_walk_file+0x227/0x620 mm/rmap.c:2905
>
> 3 locks held by syz.5.48/5754:
> ...
> #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
> i_mmap_lock_write include/linux/fs.h:548 [inline]
> #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
> hugetlbfs_punch_hole fs/hugetlbfs/inode.c:691 [inline]
> #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
> hugetlbfs_fallocate+0x4b5/0x1100
> ```
>
> 1) One task (5754) holds the i_mmap_rwsem write lock for hugetlbfs_fallocate.
> 2) While holding that lock, it blocks waiting for a folio_lock (according
> to its call trace).
> 3) This starves the other task (5749), which is waiting for the i_mmap_rwsem
> read lock to perform migrate_pages.
>
> From the report, I cannot tell who originally held the folio_lock that
> blocked task 5754. I hope this analysis is useful ...
I believe task (5749) is the one holding that folio_lock. IIUC, that's a
A-B-B-A deadlock:
1) Task (5749): Holds folio_lock, then tries to acquire i_mmap_rwsem(read lock).
2) Task (5754): Holds i_mmap_rwsem(write lock), then tries to acquire
folio_lock.
# Task (5749)
migrate_pages()
-> migrate_hugetlbs()
-> unmap_and_move_huge_page() <- Takes folio_lock!
-> remove_migration_ptes()
-> __rmap_walk_file()
-> i_mmap_lock_read() <- Waits for i_mmap_rwsem(read lock)!
# Task (5754)
hugetlbfs_fallocate()
-> hugetlbfs_punch_hole() <- Takes i_mmap_rwsem(write lock)!
-> hugetlbfs_zero_partial_page()
-> filemap_lock_hugetlb_folio()
-> filemap_lock_folio()
-> __filemap_get_folio <- Waits for folio_lock!
Thanks,
Lance
>
> Thanks,
> Lance
>
> > __down_read_common kernel/locking/rwsem.c:1261 [inline]
> > __down_read kernel/locking/rwsem.c:1274 [inline]
> > down_read+0x98/0x2e0 kernel/locking/rwsem.c:1539
> > i_mmap_lock_read include/linux/fs.h:568 [inline]
> > __rmap_walk_file+0x227/0x620 mm/rmap.c:2905
> > remove_migration_ptes mm/migrate.c:471 [inline]
> > unmap_and_move_huge_page mm/migrate.c:1520 [inline]
> > migrate_hugetlbs mm/migrate.c:1641 [inline]
> > migrate_pages+0xc98/0x2930 mm/migrate.c:2080
> > do_mbind mm/mempolicy.c:1539 [inline]
> > kernel_mbind mm/mempolicy.c:1682 [inline]
> > __do_sys_mbind mm/mempolicy.c:1756 [inline]
> > __se_sys_mbind+0xa47/0xc40 mm/mempolicy.c:1752
> > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> > do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
> > entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > RIP: 0033:0x7fd36cd8eec9
> > RSP: 002b:00007fd36dccd038 EFLAGS: 00000246 ORIG_RAX: 00000000000000ed
> > RAX: ffffffffffffffda RBX: 00007fd36cfe5fa0 RCX: 00007fd36cd8eec9
> > RDX: 0000000000000000 RSI: 0000000000800000 RDI: 0000200000001000
> > RBP: 00007fd36ce11f91 R08: 0000000000000040 R09: 0000000000000002
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> > R13: 00007fd36cfe6038 R14: 00007fd36cfe5fa0 R15: 00007ffec3386808
> > </TASK>
> > INFO: task syz.5.48:5754 blocked for more than 143 seconds.
> > Not tainted syzkaller #0
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > task:syz.5.48 state:D stack:26920 pid:5754 tgid:5747 ppid:5477 task_flags:0x400040 flags:0x00080002
> > Call Trace:
> > <TASK>
> > context_switch kernel/sched/core.c:5325 [inline]
> > __schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
> > __schedule_loop kernel/sched/core.c:7011 [inline]
> > schedule+0x165/0x360 kernel/sched/core.c:7026
> > io_schedule+0x80/0xd0 kernel/sched/core.c:7871
> > folio_wait_bit_common+0x6b0/0xb80 mm/filemap.c:1330
> > __folio_lock mm/filemap.c:1706 [inline]
> > folio_lock include/linux/pagemap.h:1141 [inline]
> > __filemap_get_folio+0x139/0xaf0 mm/filemap.c:1960
> > filemap_lock_folio include/linux/pagemap.h:820 [inline]
> > filemap_lock_hugetlb_folio include/linux/hugetlb.h:814 [inline]
> > hugetlbfs_zero_partial_page+0xae/0x610 fs/hugetlbfs/inode.c:654
> > hugetlbfs_punch_hole fs/hugetlbfs/inode.c:708 [inline]
> > hugetlbfs_fallocate+0xb91/0x1100 fs/hugetlbfs/inode.c:741
> > vfs_fallocate+0x666/0x7e0 fs/open.c:342
> > madvise_remove mm/madvise.c:1049 [inline]
> > madvise_vma_behavior+0x31b3/0x3a10 mm/madvise.c:1346
> > madvise_walk_vmas+0x51c/0xa30 mm/madvise.c:1669
> > madvise_do_behavior+0x38e/0x550 mm/madvise.c:1885
> > do_madvise+0x1bc/0x270 mm/madvise.c:1978
> > __do_sys_madvise mm/madvise.c:1987 [inline]
> > __se_sys_madvise mm/madvise.c:1985 [inline]
> > __x64_sys_madvise+0xa7/0xc0 mm/madvise.c:1985
> > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> > do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
> > entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > RIP: 0033:0x7fd36cd8eec9
> > RSP: 002b:00007fd36dcac038 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
> > RAX: ffffffffffffffda RBX: 00007fd36cfe6090 RCX: 00007fd36cd8eec9
> > RDX: 0000000000000009 RSI: 0000000000600002 RDI: 0000200000000000
> > RBP: 00007fd36ce11f91 R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> > R13: 00007fd36cfe6128 R14: 00007fd36cfe6090 R15: 00007ffec3386808
> > </TASK>
> >
> > Showing all locks held in the system:
> > 3 locks held by kworker/u4:0/12:
> > #0: ffff88801a479948 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3238 [inline]
> > #0: ffff88801a479948 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3346
> > #1: ffffc900001e7ba0 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3239 [inline]
> > #1: ffffc900001e7ba0 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3346
> > #2: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:303
> > 1 lock held by khungtaskd/26:
> > #0: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
> > #0: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
> > #0: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
> > 5 locks held by kworker/u4:6/1041:
> > #0: ffff88801b6f8948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3238 [inline]
> > #0: ffff88801b6f8948 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3346
> > #1: ffffc900025b7ba0 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3239 [inline]
> > #1: ffffc900025b7ba0 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3346
> > #2: ffffffff8f4d4c50 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xf7/0x820 net/core/net_namespace.c:669
> > #3: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: default_device_exit_batch+0xdc/0x890 net/core/dev.c:12807
> > #4: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:311 [inline]
> > #4: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x2f6/0x730 kernel/rcu/tree_exp.h:957
> > 1 lock held by dhcpcd/5017:
> > #0: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
> > #0: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: devinet_ioctl+0x323/0x1b50 net/ipv4/devinet.c:1120
> > 2 locks held by getty/5110:
> > #0: ffff88803597c0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
> > #1: ffffc9000018e2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400 drivers/tty/n_tty.c:2222
> > 1 lock held by syz.5.48/5749:
> > #0: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: i_mmap_lock_read include/linux/fs.h:568 [inline]
> > #0: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: __rmap_walk_file+0x227/0x620 mm/rmap.c:2905
> > 3 locks held by syz.5.48/5754:
> > #0: ffff88801ebe2420 (sb_writers#12){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3111 [inline]
> > #0: ffff88801ebe2420 (sb_writers#12){.+.+}-{0:0}, at: vfs_fallocate+0x5f0/0x7e0 fs/open.c:341
> > #1: ffff888011d3f348 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:980 [inline]
> > #1: ffff888011d3f348 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: hugetlbfs_punch_hole fs/hugetlbfs/inode.c:683 [inline]
> > #1: ffff888011d3f348 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: hugetlbfs_fallocate+0x3cc/0x1100 fs/hugetlbfs/inode.c:741
> > #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: i_mmap_lock_write include/linux/fs.h:548 [inline]
> > #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: hugetlbfs_punch_hole fs/hugetlbfs/inode.c:691 [inline]
> > #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: hugetlbfs_fallocate+0x4b5/0x1100 fs/hugetlbfs/inode.c:741
> > 2 locks held by syz-executor/20402:
> > #0: ffffffff8ec74400 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
> > #0: ffffffff8ec74400 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
> > #0: ffffffff8ec74400 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x23/0x250 net/core/rtnetlink.c:570
> > #1: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
> > #1: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
> > #1: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x8e9/0x1c80 net/core/rtnetlink.c:4064
> > 1 lock held by syz.4.7446/21125:
> > #0: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:343 [inline]
> > #0: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x3b9/0x730 kernel/rcu/tree_exp.h:957
> >
> > =============================================
> >
> > NMI backtrace for cpu 0
> > CPU: 0 UID: 0 PID: 26 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full)
> > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> > Call Trace:
> > <TASK>
> > dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
> > nmi_cpu_backtrace+0x39e/0x3d0 lib/nmi_backtrace.c:113
> > nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
> > trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
> > check_hung_uninterruptible_tasks kernel/hung_task.c:332 [inline]
> > watchdog+0xf60/0xfa0 kernel/hung_task.c:495
> > kthread+0x711/0x8a0 kernel/kthread.c:463
> > ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
> > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> > </TASK>
> >
> >
> > ---
> > This report is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@googlegroups.com.
> >
> > syzbot will keep track of this issue. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> >
> > If the report is already addressed, let syzbot know by replying with:
> > #syz fix: exact-commit-title
> >
> > If you want syzbot to run the reproducer, reply with:
> > #syz test: git://repo/address.git branch-or-commit-hash
> > If you attach or paste a git patch, syzbot will apply it before testing.
> >
> > If you want to overwrite report's subsystems, reply with:
> > #syz set subsystems: new-subsystem
> > (See the list of subsystem names on the web dashboard)
> >
> > If the report is a duplicate of another one, reply with:
> > #syz dup: exact-subject-of-another-report
> >
> > If you want to undo deduplication, reply with:
> > #syz undup
> >
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [syzbot] [mm?] INFO: task hung in __rmap_walk_file
2025-10-11 6:10 ` Lance Yang
@ 2025-10-13 11:23 ` Harry Yoo
0 siblings, 0 replies; 4+ messages in thread
From: Harry Yoo @ 2025-10-13 11:23 UTC (permalink / raw)
To: Lance Yang
Cc: syzbot, Liam.Howlett, akpm, david, jannh, linux-kernel, linux-mm,
lorenzo.stoakes, riel, syzkaller-bugs, vbabka, Muchun Song,
Oscar Salvador
On Sat, Oct 11, 2025 at 02:10:14PM +0800, Lance Yang wrote:
> On Sat, Oct 11, 2025 at 11:11 AM Lance Yang <lance.yang@linux.dev> wrote:
> >
> > On Sat, Oct 11, 2025 at 4:49 AM syzbot
> > <syzbot+2d9c96466c978346b55f@syzkaller.appspotmail.com> wrote:
> > >
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit: 5472d60c129f Merge tag 'trace-v6.18-2' of git://git.kernel..
> > > git tree: upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=16d69304580000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=5b213914b883d014
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=2d9c96466c978346b55f
> > > compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=133e89e2580000
> > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17f3ba7c580000
> > >
> > > Downloadable assets:
> > > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-5472d60c.raw.xz
> > > vmlinux: https://storage.googleapis.com/syzbot-assets/af61e8db8b22/vmlinux-5472d60c.xz
> > > kernel image: https://storage.googleapis.com/syzbot-assets/a2c11e401d8a/bzImage-5472d60c.xz
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+2d9c96466c978346b55f@syzkaller.appspotmail.com
> > >
> > > INFO: task syz.5.48:5749 blocked for more than 143 seconds.
> > > Not tainted syzkaller #0
> > > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > > task:syz.5.48 state:D stack:27656 pid:5749 tgid:5747 ppid:5477 task_flags:0x400040 flags:0x00080002
> > > Call Trace:
> > > <TASK>
> > > context_switch kernel/sched/core.c:5325 [inline]
> > > __schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
> > > __schedule_loop kernel/sched/core.c:7011 [inline]
> > > schedule+0x165/0x360 kernel/sched/core.c:7026
> > > schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7083
> > > rwsem_down_read_slowpath+0x5fd/0x8f0 kernel/locking/rwsem.c:1086
> >
> > It would be great if CONFIG_DETECT_HUNG_TASK_BLOCKER was set, as it could
> > point directly to the blocker. However, the lockdep output at the end of
> > the report already gives us the crucial clue :)
> >
> > ```
> > 1 lock held by syz.5.48/5749:
> > #0: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
> > i_mmap_lock_read include/linux/fs.h:568 [inline]
> > #0: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
> > __rmap_walk_file+0x227/0x620 mm/rmap.c:2905
> >
> > 3 locks held by syz.5.48/5754:
> > ...
> > #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
> > i_mmap_lock_write include/linux/fs.h:548 [inline]
> > #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
> > hugetlbfs_punch_hole fs/hugetlbfs/inode.c:691 [inline]
> > #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at:
> > hugetlbfs_fallocate+0x4b5/0x1100
> > ```
> >
> > 1) One task (5754) holds the i_mmap_rwsem write lock for hugetlbfs_fallocate.
> > 2) While holding that lock, it blocks waiting for a folio_lock (according
> > to its call trace).
> > 3) This starves the other task (5749), which is waiting for the i_mmap_rwsem
> > read lock to perform migrate_pages.
> >
> > From the report, I cannot tell who originally held the folio_lock that
> > blocked task 5754. I hope this analysis is useful ...
>
> I believe task (5749) is the one holding that folio_lock. IIUC, that's a
> A-B-B-A deadlock:
>
> 1) Task (5749): Holds folio_lock, then tries to acquire i_mmap_rwsem(read lock).
> 2) Task (5754): Holds i_mmap_rwsem(write lock), then tries to acquire
> folio_lock.
[+Cc HUGETLB SUBSYSTEM folks]
> # Task (5749)
> migrate_pages()
> -> migrate_hugetlbs()
> -> unmap_and_move_huge_page() <- Takes folio_lock!
> -> remove_migration_ptes()
> -> __rmap_walk_file()
> -> i_mmap_lock_read() <- Waits for i_mmap_rwsem(read lock)!
>
> # Task (5754)
> hugetlbfs_fallocate()
> -> hugetlbfs_punch_hole() <- Takes i_mmap_rwsem(write lock)!
> -> hugetlbfs_zero_partial_page()
> -> filemap_lock_hugetlb_folio()
> -> filemap_lock_folio()
> -> __filemap_get_folio <- Waits for folio_lock!
So this is against the locking order mentioned in mm/rmap.c?
The order should be mapping->i_mmap_rwsem -> folio_lock instead of
the other way around, or it should use trylock variant instead of folio_lock()?
--
Cheers,
Harry / Hyeonggon
> Thanks,
> Lance
>
>
> >
> > Thanks,
> > Lance
> >
> > > __down_read_common kernel/locking/rwsem.c:1261 [inline]
> > > __down_read kernel/locking/rwsem.c:1274 [inline]
> > > down_read+0x98/0x2e0 kernel/locking/rwsem.c:1539
> > > i_mmap_lock_read include/linux/fs.h:568 [inline]
> > > __rmap_walk_file+0x227/0x620 mm/rmap.c:2905
> > > remove_migration_ptes mm/migrate.c:471 [inline]
> > > unmap_and_move_huge_page mm/migrate.c:1520 [inline]
> > > migrate_hugetlbs mm/migrate.c:1641 [inline]
> > > migrate_pages+0xc98/0x2930 mm/migrate.c:2080
> > > do_mbind mm/mempolicy.c:1539 [inline]
> > > kernel_mbind mm/mempolicy.c:1682 [inline]
> > > __do_sys_mbind mm/mempolicy.c:1756 [inline]
> > > __se_sys_mbind+0xa47/0xc40 mm/mempolicy.c:1752
> > > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> > > do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
> > > entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > > RIP: 0033:0x7fd36cd8eec9
> > > RSP: 002b:00007fd36dccd038 EFLAGS: 00000246 ORIG_RAX: 00000000000000ed
> > > RAX: ffffffffffffffda RBX: 00007fd36cfe5fa0 RCX: 00007fd36cd8eec9
> > > RDX: 0000000000000000 RSI: 0000000000800000 RDI: 0000200000001000
> > > RBP: 00007fd36ce11f91 R08: 0000000000000040 R09: 0000000000000002
> > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> > > R13: 00007fd36cfe6038 R14: 00007fd36cfe5fa0 R15: 00007ffec3386808
> > > </TASK>
> > > INFO: task syz.5.48:5754 blocked for more than 143 seconds.
> > > Not tainted syzkaller #0
> > > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > > task:syz.5.48 state:D stack:26920 pid:5754 tgid:5747 ppid:5477 task_flags:0x400040 flags:0x00080002
> > > Call Trace:
> > > <TASK>
> > > context_switch kernel/sched/core.c:5325 [inline]
> > > __schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
> > > __schedule_loop kernel/sched/core.c:7011 [inline]
> > > schedule+0x165/0x360 kernel/sched/core.c:7026
> > > io_schedule+0x80/0xd0 kernel/sched/core.c:7871
> > > folio_wait_bit_common+0x6b0/0xb80 mm/filemap.c:1330
> > > __folio_lock mm/filemap.c:1706 [inline]
> > > folio_lock include/linux/pagemap.h:1141 [inline]
> > > __filemap_get_folio+0x139/0xaf0 mm/filemap.c:1960
> > > filemap_lock_folio include/linux/pagemap.h:820 [inline]
> > > filemap_lock_hugetlb_folio include/linux/hugetlb.h:814 [inline]
> > > hugetlbfs_zero_partial_page+0xae/0x610 fs/hugetlbfs/inode.c:654
> > > hugetlbfs_punch_hole fs/hugetlbfs/inode.c:708 [inline]
> > > hugetlbfs_fallocate+0xb91/0x1100 fs/hugetlbfs/inode.c:741
> > > vfs_fallocate+0x666/0x7e0 fs/open.c:342
> > > madvise_remove mm/madvise.c:1049 [inline]
> > > madvise_vma_behavior+0x31b3/0x3a10 mm/madvise.c:1346
> > > madvise_walk_vmas+0x51c/0xa30 mm/madvise.c:1669
> > > madvise_do_behavior+0x38e/0x550 mm/madvise.c:1885
> > > do_madvise+0x1bc/0x270 mm/madvise.c:1978
> > > __do_sys_madvise mm/madvise.c:1987 [inline]
> > > __se_sys_madvise mm/madvise.c:1985 [inline]
> > > __x64_sys_madvise+0xa7/0xc0 mm/madvise.c:1985
> > > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> > > do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
> > > entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > > RIP: 0033:0x7fd36cd8eec9
> > > RSP: 002b:00007fd36dcac038 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
> > > RAX: ffffffffffffffda RBX: 00007fd36cfe6090 RCX: 00007fd36cd8eec9
> > > RDX: 0000000000000009 RSI: 0000000000600002 RDI: 0000200000000000
> > > RBP: 00007fd36ce11f91 R08: 0000000000000000 R09: 0000000000000000
> > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> > > R13: 00007fd36cfe6128 R14: 00007fd36cfe6090 R15: 00007ffec3386808
> > > </TASK>
> > >
> > > Showing all locks held in the system:
> > > 3 locks held by kworker/u4:0/12:
> > > #0: ffff88801a479948 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3238 [inline]
> > > #0: ffff88801a479948 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3346
> > > #1: ffffc900001e7ba0 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3239 [inline]
> > > #1: ffffc900001e7ba0 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3346
> > > #2: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:303
> > > 1 lock held by khungtaskd/26:
> > > #0: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
> > > #0: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
> > > #0: ffffffff8e13d320 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
> > > 5 locks held by kworker/u4:6/1041:
> > > #0: ffff88801b6f8948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3238 [inline]
> > > #0: ffff88801b6f8948 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3346
> > > #1: ffffc900025b7ba0 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3239 [inline]
> > > #1: ffffc900025b7ba0 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3346
> > > #2: ffffffff8f4d4c50 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xf7/0x820 net/core/net_namespace.c:669
> > > #3: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: default_device_exit_batch+0xdc/0x890 net/core/dev.c:12807
> > > #4: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:311 [inline]
> > > #4: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x2f6/0x730 kernel/rcu/tree_exp.h:957
> > > 1 lock held by dhcpcd/5017:
> > > #0: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
> > > #0: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: devinet_ioctl+0x323/0x1b50 net/ipv4/devinet.c:1120
> > > 2 locks held by getty/5110:
> > > #0: ffff88803597c0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
> > > #1: ffffc9000018e2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400 drivers/tty/n_tty.c:2222
> > > 1 lock held by syz.5.48/5749:
> > > #0: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: i_mmap_lock_read include/linux/fs.h:568 [inline]
> > > #0: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: __rmap_walk_file+0x227/0x620 mm/rmap.c:2905
> > > 3 locks held by syz.5.48/5754:
> > > #0: ffff88801ebe2420 (sb_writers#12){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3111 [inline]
> > > #0: ffff88801ebe2420 (sb_writers#12){.+.+}-{0:0}, at: vfs_fallocate+0x5f0/0x7e0 fs/open.c:341
> > > #1: ffff888011d3f348 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:980 [inline]
> > > #1: ffff888011d3f348 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: hugetlbfs_punch_hole fs/hugetlbfs/inode.c:683 [inline]
> > > #1: ffff888011d3f348 (&sb->s_type->i_mutex_key#20){+.+.}-{4:4}, at: hugetlbfs_fallocate+0x3cc/0x1100 fs/hugetlbfs/inode.c:741
> > > #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: i_mmap_lock_write include/linux/fs.h:548 [inline]
> > > #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: hugetlbfs_punch_hole fs/hugetlbfs/inode.c:691 [inline]
> > > #2: ffff888011d3f618 (&hugetlbfs_i_mmap_rwsem_key){++++}-{4:4}, at: hugetlbfs_fallocate+0x4b5/0x1100 fs/hugetlbfs/inode.c:741
> > > 2 locks held by syz-executor/20402:
> > > #0: ffffffff8ec74400 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
> > > #0: ffffffff8ec74400 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
> > > #0: ffffffff8ec74400 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x23/0x250 net/core/rtnetlink.c:570
> > > #1: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
> > > #1: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
> > > #1: ffffffff8f4e1ac8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x8e9/0x1c80 net/core/rtnetlink.c:4064
> > > 1 lock held by syz.4.7446/21125:
> > > #0: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:343 [inline]
> > > #0: ffffffff8e142db8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x3b9/0x730 kernel/rcu/tree_exp.h:957
> > >
> > > =============================================
> > >
> > > NMI backtrace for cpu 0
> > > CPU: 0 UID: 0 PID: 26 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full)
> > > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> > > Call Trace:
> > > <TASK>
> > > dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
> > > nmi_cpu_backtrace+0x39e/0x3d0 lib/nmi_backtrace.c:113
> > > nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
> > > trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
> > > check_hung_uninterruptible_tasks kernel/hung_task.c:332 [inline]
> > > watchdog+0xf60/0xfa0 kernel/hung_task.c:495
> > > kthread+0x711/0x8a0 kernel/kthread.c:463
> > > ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
> > > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> > > </TASK>
> > >
> > >
> > > ---
> > > This report is generated by a bot. It may contain errors.
> > > See https://goo.gl/tpsmEJ for more information about syzbot.
> > > syzbot engineers can be reached at syzkaller@googlegroups.com.
> > >
> > > syzbot will keep track of this issue. See:
> > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > >
> > > If the report is already addressed, let syzbot know by replying with:
> > > #syz fix: exact-commit-title
> > >
> > > If you want syzbot to run the reproducer, reply with:
> > > #syz test: git://repo/address.git branch-or-commit-hash
> > > If you attach or paste a git patch, syzbot will apply it before testing.
> > >
> > > If you want to overwrite report's subsystems, reply with:
> > > #syz set subsystems: new-subsystem
> > > (See the list of subsystem names on the web dashboard)
> > >
> > > If the report is a duplicate of another one, reply with:
> > > #syz dup: exact-subject-of-another-report
> > >
> > > If you want to undo deduplication, reply with:
> > > #syz undup
> > >
>
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2025-10-13 11:24 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2025-10-10 20:49 [syzbot] [mm?] INFO: task hung in __rmap_walk_file syzbot
2025-10-11 3:11 ` Lance Yang
2025-10-11 6:10 ` Lance Yang
2025-10-13 11:23 ` Harry Yoo
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