syzbot

INFO: task syz-executor264:5867 blocked for more than 143 seconds.
      Not tainted 6.16.0-rc6-syzkaller-00253-g4871b7cb27f4 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor264 state:D stack:25128 pid:5867  tgid:5867  ppid:5864   task_flags:0x400100 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5397 [inline]
 __schedule+0x16f5/0x4d00 kernel/sched/core.c:6786
 __schedule_loop kernel/sched/core.c:6864 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6879
 netfs_wait_for_outstanding_io include/linux/netfs.h:552 [inline]
 v9fs_evict_inode+0x170/0x320 fs/9p/vfs_inode.c:348
 evict+0x504/0x9c0 fs/inode.c:810
 __dentry_kill+0x209/0x660 fs/dcache.c:669
 dput+0x19f/0x2b0 fs/dcache.c:911
 shrink_dcache_for_umount+0xa0/0x170 fs/dcache.c:1621
 generic_shutdown_super+0x67/0x2c0 fs/super.c:621
 kill_anon_super+0x3b/0x70 fs/super.c:1282
 v9fs_kill_super+0x4c/0x90 fs/9p/vfs_super.c:193
 deactivate_locked_super+0xbc/0x130 fs/super.c:474
 cleanup_mnt+0x425/0x4c0 fs/namespace.c:1417
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 ptrace_notify+0x281/0x2c0 kernel/signal.c:2520
 ptrace_report_syscall include/linux/ptrace.h:415 [inline]
 ptrace_report_syscall_exit include/linux/ptrace.h:477 [inline]
 syscall_exit_work+0xc6/0x1d0 kernel/entry/common.c:173
 syscall_exit_to_user_mode_work include/linux/entry-common.h:412 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
 do_syscall_64+0x2ad/0x3b0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9a7c809647
RSP: 002b:00007ffdc83e2bd8 EFLAGS: 00000206 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 000000000002165d RCX: 00007f9a7c809647
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffdc83e2c90
RBP: 00007ffdc83e2c90 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000206 R12: 00007ffdc83e3d00
R13: 000055558cc3e6c0 R14: 00007ffdc83e3d00 R15: 0000000000000001
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
 #0: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6770
1 lock held by klogd/5200:
 #0: ffff8880b8739f98 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:606
2 locks held by getty/5601:
 #0: ffff888030f7f0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000333b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400 drivers/tty/n_tty.c:2222
1 lock held by syz-executor264/5867:
 #0: ffff88807b61a0e0 (&type->s_umount_key#42){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
 #0: ffff88807b61a0e0 (&type->s_umount_key#42){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
 #0: ffff88807b61a0e0 (&type->s_umount_key#42){+.+.}-{4:4}, at: deactivate_super+0xa9/0xe0 fs/super.c:506

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Not tainted 6.16.0-rc6-syzkaller-00253-g4871b7cb27f4 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:307 [inline]
 watchdog+0xfee/0x1030 kernel/hung_task.c:470
 kthread+0x711/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted 6.16.0-rc6-syzkaller-00253-g4871b7cb27f4 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:can_migrate_task+0xd6/0xba0 kernel/sched/fair.c:9401
Code: 83 c7 18 4c 89 ff be ff ff ff ff e8 d4 86 d6 09 85 c0 0f 84 1a 07 00 00 4d 8d ae 8c 05 00 00 4c 89 ea 48 c1 ea 03 0f b6 04 1a <84> c0 0f 85 38 07 00 00 41 0f b6 6d 00 40 f6 c5 08 74 14 40 80 e5
RSP: 0018:ffffc90000a086f8 EFLAGS: 00000017
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: 3dd272d90763e000
RDX: 1ffff110037500b1 RSI: ffffffff8db83cac RDI: ffffffff8be28c00
RBP: ffffc90000a08c38 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff520001410d8 R12: ffffc90000a08b40
R13: ffff88801ba8058c R14: ffff88801ba80000 R15: ffff8880b8639f98
FS:  0000000000000000(0000) GS:ffff888125d23000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000561f24125660 CR3: 000000000df38000 CR4: 0000000000350ef0
Call Trace:
 <IRQ>
 detach_tasks kernel/sched/fair.c:9595 [inline]
 sched_balance_rq+0x35e3/0x57a0 kernel/sched/fair.c:11822
 sched_balance_domains+0x49f/0x9e0 kernel/sched/fair.c:12243
 _nohz_idle_balance+0x59d/0x810 kernel/sched/fair.c:12678
 handle_softirqs+0x286/0x870 kernel/softirq.c:579
 __do_softirq kernel/softirq.c:613 [inline]
 invoke_softirq kernel/softirq.c:453 [inline]
 __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
 instr_sysvec_call_function_single arch/x86/kernel/smp.c:266 [inline]
 sysvec_call_function_single+0xa3/0xc0 arch/x86/kernel/smp.c:266
 </IRQ>
 <TASK>
 asm_sysvec_call_function_single+0x1a/0x20 arch/x86/include/asm/idtentry.h:709
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:82
Code: 3e cc a2 f5 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d d3 bd 1a 00 f3 0f 1e fa fb f4 <e9> 13 cc a2 f5 cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90000197de0 EFLAGS: 000002c2
RAX: 3dd272d90763e000 RBX: ffffffff81976a48 RCX: 3dd272d90763e000
RDX: 0000000000000001 RSI: ffffffff8d9960e1 RDI: ffffffff8be28c00
RBP: ffffc90000197f20 R08: ffff8880b8732f5b R09: 1ffff110170e65eb
R10: dffffc0000000000 R11: ffffed10170e65ec R12: ffffffff8fa1d6f0
R13: 0000000000000001 R14: 0000000000000001 R15: 1ffff110039d2b40
 arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:749
 default_idle_call+0x74/0xb0 kernel/sched/idle.c:117
 cpuidle_idle_call kernel/sched/idle.c:185 [inline]
 do_idle+0x1e8/0x510 kernel/sched/idle.c:325
 cpu_startup_entry+0x44/0x60 kernel/sched/idle.c:423
 start_secondary+0x101/0x110 arch/x86/kernel/smpboot.c:315
 common_startup_64+0x13e/0x147
 </TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.811 msecs