syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	1-...!: (1 GPs behind) idle=1494/1/0x4000000000000000 softirq=29767/29774 fqs=1084
rcu: 	(detected by 0, t=10502 jiffies, g=32065, q=36210 ncpus=2)
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 8234 Comm: syz.8.446 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:__lock_acquire+0x1bdf/0x7c80 kernel/locking/lockdep.c:5168
Code: 20 01 00 00 0e 36 e0 45 48 8b 84 24 f0 00 00 00 42 c7 04 00 00 00 00 00 4a c7 44 00 0b 00 00 00 00 42 c7 44 00 17 00 00 00 00 <42> c6 44 00 1b 00 65 48 8b 04 25 28 00 00 00 48 3b 84 24 00 02 00
RSP: 0018:ffffc900001f07a0 EFLAGS: 00000097
RAX: 1ffff9200003e118 RBX: ffff88804b950ad8 RCX: 0000000000048000
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90d94500
RBP: ffffc900001f09e8 R08: dffffc0000000000 R09: 1ffffffff21b28a0
R10: dffffc0000000000 R11: fffffbfff21b28a1 R12: 798a1fc9a8163414
R13: ffff88804b950000 R14: 0000000000000001 R15: ffff88804b950b50
FS:  00007f1b46fb46c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1b46fb3f98 CR3: 000000004c424000 CR4: 00000000003506e0
Call Trace:
 <IRQ>
 lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
 debug_objects_fill_pool+0x92/0x6b0 lib/debugobjects.c:615
 debug_object_activate+0x36/0x4b0 lib/debugobjects.c:705
 debug_hrtimer_activate kernel/time/hrtimer.c:450 [inline]
 debug_activate kernel/time/hrtimer.c:505 [inline]
 enqueue_hrtimer+0x30/0x370 kernel/time/hrtimer.c:1108
 __run_hrtimer kernel/time/hrtimer.c:1767 [inline]
 __hrtimer_run_queues+0x637/0xc40 kernel/time/hrtimer.c:1814
 hrtimer_interrupt+0x3c9/0x9c0 kernel/time/hrtimer.c:1876
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
 __sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0x9f/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xa9/0x110 kernel/locking/spinlock.c:194
Code: 74 05 e8 0a d9 1a f7 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> e2 53 ea f6 65 8b 05 d3 9a 92 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc900037a7b60 EFLAGS: 00000206
RAX: 75c1cbbde1951e00 RBX: 0000000000000a06 RCX: 75c1cbbde1951e00
RDX: dffffc0000000000 RSI: ffffffff8aaabce0 RDI: 0000000000000001
RBP: ffffc900037a7bf0 R08: ffffffff90d94507 R09: 1ffffffff21b28a0
R10: dffffc0000000000 R11: fffffbfff21b28a1 R12: dffffc0000000000
R13: ffff8880b8e2b700 R14: ffff8880b8e2b700 R15: 1ffff920006f4f6c
 clock_was_set+0x64e/0x7d0 kernel/time/hrtimer.c:993
 do_settimeofday64+0x579/0x720 kernel/time/timekeeping.c:1345
 __do_sys_clock_settime kernel/time/posix-timers.c:1130 [inline]
 __se_sys_clock_settime kernel/time/posix-timers.c:1114 [inline]
 __x64_sys_clock_settime+0x227/0x270 kernel/time/posix-timers.c:1114
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f1b48d8f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1b46fb4038 EFLAGS: 00000246 ORIG_RAX: 00000000000000e3
RAX: ffffffffffffffda RBX: 00007f1b48fe6180 RCX: 00007f1b48d8f749
RDX: 0000000000000000 RSI: 0000200000000240 RDI: 0000000000000000
RBP: 00007f1b48e13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1b48fe6218 R14: 00007f1b48fe6180 R15: 00007fff3c601cc8
 </TASK>
rcu: rcu_preempt kthread starved for 8333 jiffies! g32065 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:26568 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
 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>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 PID: 6133 Comm: kworker/u4:9 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: writeback wb_workfn (flush-8:0)
RIP: 0010:csd_lock_wait kernel/smp.c:311 [inline]
RIP: 0010:smp_call_function_many_cond+0xddf/0x1130 kernel/smp.c:855
Code: 45 8b 2c 24 44 89 ee 83 e6 01 31 ff e8 6a d7 0a 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 a5 d3 0a 00 eb 38 f3 90 <42> 0f b6 04 2b 84 c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 89 d3
RSP: 0000:ffffc900039e6360 EFLAGS: 00000293
RAX: ffffffff817abd37 RBX: 1ffff110171e826d RCX: ffff88802b705a00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900039e64e0 R08: ffffc900039e62e7 R09: 1ffff9200073cc5c
R10: dffffc0000000000 R11: fffff5200073cc5d R12: ffff8880b8f41368
R13: dffffc0000000000 R14: ffff8880b8e3d148 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1141700ce0 CR3: 000000004df1c000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1022
 __flush_tlb_multi arch/x86/include/asm/paravirt.h:87 [inline]
 flush_tlb_multi arch/x86/mm/tlb.c:990 [inline]
 flush_tlb_mm_range+0x41e/0x690 arch/x86/mm/tlb.c:1078
 flush_tlb_page arch/x86/include/asm/tlbflush.h:255 [inline]
 ptep_clear_flush+0x120/0x170 mm/pgtable-generic.c:101
 page_vma_mkclean_one+0x413/0x720 mm/rmap.c:962
 page_mkclean_one+0x1ec/0x3b0 mm/rmap.c:1003
 rmap_walk_file+0x3f8/0x760 mm/rmap.c:2503
 rmap_walk mm/rmap.c:2521 [inline]
 folio_mkclean+0x1c8/0x330 mm/rmap.c:1035
 folio_clear_dirty_for_io+0x20e/0xc30 mm/page-writeback.c:2918
 mpage_submit_folio+0x7d/0x3c0 fs/ext4/inode.c:1889
 mpage_process_page_bufs+0x6e1/0x8f0 fs/ext4/inode.c:2021
 mpage_prepare_extent_to_map+0xde9/0x1c80 fs/ext4/inode.c:2529
 ext4_do_writepages+0xb19/0x38d0 fs/ext4/inode.c:2671
 ext4_writepages+0x1a8/0x2f0 fs/ext4/inode.c:2807
 do_writepages+0x3a2/0x600 mm/page-writeback.c:2575
 __writeback_single_inode+0x153/0xee0 fs/fs-writeback.c:1635
 writeback_sb_inodes+0x77c/0xef0 fs/fs-writeback.c:1926
 __writeback_inodes_wb+0x111/0x240 fs/fs-writeback.c:1997
 wb_writeback+0x464/0xba0 fs/fs-writeback.c:2107
 wb_check_old_data_flush fs/fs-writeback.c:2211 [inline]
 wb_do_writeback fs/fs-writeback.c:2264 [inline]
 wb_workfn+0xabc/0xe20 fs/fs-writeback.c:2292
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 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>