syzbot

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BUG: KCSAN: data-race in io_wq_worker / kthread_is_per_cpu

write to 0xffff8881589f2768 of 8 bytes by task 25819 on cpu 0:
 io_worker_exit io_uring/io-wq.c:258 [inline]
 io_wq_worker+0x78f/0x870 io_uring/io-wq.c:740
 ret_from_fork+0x11f/0x1b0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff8881589f2768 of 8 bytes by task 25820 on cpu 1:
 __to_kthread kernel/kthread.c:100 [inline]
 kthread_is_per_cpu+0x1c/0x90 kernel/kthread.c:685
 can_migrate_task+0x49/0x200 kernel/sched/fair.c:9314
 detach_tasks kernel/sched/fair.c:9487 [inline]
 sched_balance_rq+0x14aa/0x1e20 kernel/sched/fair.c:11714
 sched_balance_newidle+0x16a/0x340 kernel/sched/fair.c:12762
 pick_next_task_fair+0x3d/0x2b0 kernel/sched/fair.c:8835
 __pick_next_task kernel/sched/core.c:6001 [inline]
 pick_next_task kernel/sched/core.c:6520 [inline]
 __schedule+0x2e5/0xb30 kernel/sched/core.c:6902
 do_task_dead+0x43/0xb0 kernel/sched/core.c:6982
 do_exit+0x113e/0x15c0 kernel/exit.c:1004
 call_usermodehelper_exec_async+0x247/0x250 kernel/umh.c:122
 ret_from_fork+0x11f/0x1b0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0xffff88815687f300 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 25820 Comm: kworker/u8:8 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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