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BUG: KCSAN: data-race in exit_signals / kthread_unpark

write to 0xffff8880695e4024 of 4 bytes by task 12810 on cpu 1:
 exit_signals+0x124/0x580 kernel/signal.c:2831
 do_exit+0x19a/0x16a0 kernel/exit.c:762
 kthread+0x215/0x230 kernel/kthread.c:294
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff8880695e4024 of 4 bytes by task 12794 on cpu 0:
 to_kthread kernel/kthread.c:83 [inline]
 kthread_unpark+0x1f/0x150 kernel/kthread.c:511
 kthread_stop+0xa3/0x310 kernel/kthread.c:594
 kthread_destroy_worker+0x9f/0x100 kernel/kthread.c:1224
 kvm_free_pit+0x108/0x140 arch/x86/kvm/i8254.c:744
 kvm_arch_sync_events+0x29/0x30 arch/x86/kvm/x86.c:9966
 kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:857 [inline]
 kvm_put_kvm+0x166/0xad0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:898
 kvm_vcpu_release+0x2c/0x30 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3042
 __fput+0x246/0x4d0 fs/file_table.c:281
 ____fput+0x11/0x20 fs/file_table.c:314
 task_work_run+0x8e/0x110 kernel/task_work.c:135
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:139 [inline]
 exit_to_user_mode_prepare+0x1b2/0x210 kernel/entry/common.c:166
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:241
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12794 Comm: syz-executor.5 Not tainted 5.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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