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BUG: KCSAN: data-race in free_kthread_struct / kthread_is_per_cpu

write to 0xffff8881234e5128 of 8 bytes by task 11850 on cpu 1:
 free_kthread_struct+0x6f/0xb0 kernel/kthread.c:143
 begin_new_exec+0xc3a/0x1060 fs/exec.c:1312
 load_elf_binary+0x62a/0x1970 fs/binfmt_elf.c:1002
 search_binary_handler fs/exec.c:1726 [inline]
 exec_binprm+0x1d9/0x800 fs/exec.c:1767
 bprm_execve+0x379/0x4e0 fs/exec.c:1836
 kernel_execve+0x62b/0x660 fs/exec.c:1997
 call_usermodehelper_exec_async+0x1a6/0x250 kernel/umh.c:112
 ret_from_fork+0x1f/0x30

read to 0xffff8881234e5128 of 8 bytes by task 1855 on cpu 0:
 __to_kthread kernel/kthread.c:92 [inline]
 kthread_is_per_cpu+0x18/0x80 kernel/kthread.c:606
 can_migrate_task+0x13/0x1b0 kernel/sched/fair.c:7807
 detach_tasks+0xab/0x380 kernel/sched/fair.c:7971
 load_balance+0x7c3/0xcd0 kernel/sched/fair.c:9960
 newidle_balance+0x168/0x340 kernel/sched/fair.c:10969
 pick_next_task_fair+0x37/0x260 kernel/sched/fair.c:7387
 __pick_next_task kernel/sched/core.c:5695 [inline]
 pick_next_task kernel/sched/core.c:6204 [inline]
 __schedule+0x270/0x6c0 kernel/sched/core.c:6352
 schedule+0x71/0xa0 kernel/sched/core.c:6460
 do_wait+0x51f/0x670 kernel/exit.c:1537
 kernel_wait+0x4e/0xc0 kernel/exit.c:1698
 call_usermodehelper_exec_sync kernel/umh.c:139 [inline]
 call_usermodehelper_exec_work+0x98/0x150 kernel/umh.c:166
 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289
 worker_thread+0x618/0xa70 kernel/workqueue.c:2436
 kthread+0x1a9/0x1e0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30

value changed: 0xffff888127c51380 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1855 Comm: kworker/u4:6 Not tainted 5.18.0-rc7-syzkaller-00048-gf993aed406ea-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_unbound call_usermodehelper_exec_work
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