syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P20631/1:b..l P20644/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=96977, q=120 ncpus=2)
task:syz.2.4553      state:R  running task     stack:27592 pid:20644 ppid:14884  flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6867
 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6891
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
 __raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_unlock+0x3a/0x40 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 zap_pte_range mm/memory.c:1523 [inline]
 zap_pmd_range mm/memory.c:1571 [inline]
 zap_pud_range mm/memory.c:1600 [inline]
 zap_p4d_range mm/memory.c:1621 [inline]
 unmap_page_range+0x2315/0x3000 mm/memory.c:1642
 unmap_vmas+0x286/0x3f0 mm/memory.c:1732
 exit_mmap+0x238/0xb90 mm/mmap.c:3302
 __mmput+0x118/0x3c0 kernel/fork.c:1357
 exit_mm+0x24a/0x350 kernel/exit.c:570
 do_exit+0x8dd/0x2460 kernel/exit.c:871
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1026
 get_signal+0x12fc/0x13f0 kernel/signal.c:2902
 arch_do_signal_or_restart+0xc2/0x800 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
task:syz.0.4546      state:R  running task     stack:26696 pid:20631 ppid:14002  flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6867
 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6891
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
 __raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_unlock+0x3a/0x40 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 zap_pte_range mm/memory.c:1523 [inline]
 zap_pmd_range mm/memory.c:1571 [inline]
 zap_pud_range mm/memory.c:1600 [inline]
 zap_p4d_range mm/memory.c:1621 [inline]
 unmap_page_range+0x2315/0x3000 mm/memory.c:1642
 unmap_vmas+0x286/0x3f0 mm/memory.c:1732
 exit_mmap+0x238/0xb90 mm/mmap.c:3302
 __mmput+0x118/0x3c0 kernel/fork.c:1357
 copy_process+0x298f/0x3dc0 kernel/fork.c:2768
 kernel_clone+0x24b/0x8a0 kernel/fork.c:2917
 __do_sys_clone kernel/fork.c:3060 [inline]
 __se_sys_clone kernel/fork.c:3044 [inline]
 __x64_sys_clone+0x1b7/0x230 kernel/fork.c:3044
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd86c99ce59
RSP: 002b:00007fd86d849fd8 EFLAGS: 00000206 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007fd86cc16090 RCX: 00007fd86c99ce59
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020083400
RBP: 00007fd86ca32d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007fd86cc16128 R14: 00007fd86cc16090 R15: 00007ffed71971b8
 </TASK>
rcu: rcu_preempt kthread starved for 10511 jiffies! g96977 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
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:26920 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 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:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 20639 Comm: syz.3.4554 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:pv_native_safe_halt+0xf/0x10 arch/x86/kernel/paravirt.c:148
Code: 88 1f 02 c3 cc cc cc cc cc cc cc f3 0f 1e fa 0f 0b 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 66 90 0f 00 2d 43 e4 3f 00 fb f4 <c3> 66 0f 1f 00 55 41 57 41 56 41 54 53 50 8b 2f eb 2e 41 89 de 80
RSP: 0018:ffffc9000c78f878 EFLAGS: 000002d3
RAX: ffffffff813aa578 RBX: 0000000000000003 RCX: ffff888025f03c00
RDX: 0000000000000000 RSI: ffffffff8acacbe0 RDI: ffffffff8b1c9c20
RBP: ffffc9000c78f950 R08: ffffffff911cd5ff R09: 1ffffffff2239abf
R10: dffffc0000000000 R11: fffffbfff2239ac0 R12: dffffc0000000000
R13: 0000000000000200 R14: 0000000000000003 R15: 1ffff920018f1f14
FS:  000055557455c500(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2ef03ff8 CR3: 000000005c1fe000 CR4: 00000000003506e0
DR0: 0000200000000300 DR1: 0000200000000300 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
 kvm_wait+0x23d/0x2a0 arch/x86/kernel/kvm.c:1058
 pv_wait arch/x86/include/asm/paravirt.h:598 [inline]
 pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:470 [inline]
 __pv_queued_spin_lock_slowpath+0x61a/0x9d0 kernel/locking/qspinlock.c:511
 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:586 [inline]
 queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
 queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
 do_raw_spin_lock+0x23e/0x2c0 kernel/locking/spinlock_debug.c:115
 spin_lock include/linux/spinlock.h:351 [inline]
 futex_unqueue+0x4e/0xf0 kernel/futex/core.c:597
 futex_wait+0x1f4/0x5e0 kernel/futex/waitwake.c:660
 do_futex+0x2ff/0x3e0 kernel/futex/syscalls.c:134
 __do_sys_futex kernel/futex/syscalls.c:211 [inline]
 __se_sys_futex+0x3a9/0x440 kernel/futex/syscalls.c:192
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd714b9ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd02462a38 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 00000000000b8ea3 RCX: 00007fd714b9ce59
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fd714e15fac
RBP: 0000000000000032 R08: 0000000000745d1e R09: 0000000000000000
R10: 00007ffd02462b40 R11: 0000000000000246 R12: 00007ffd02462b60
R13: 00007fd714e15fac R14: 00000000000b8ed5 R15: 00007ffd02462b40
 </TASK>