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BUG: KCSAN: data-race in __percpu_ref_switch_mode / io_sq_thread

write to 0xffff88810a7b0c00 of 8 bytes by task 18482 on cpu 0:
 __percpu_ref_switch_to_atomic lib/percpu-refcount.c:216 [inline]
 __percpu_ref_switch_mode+0x19a/0x390 lib/percpu-refcount.c:273
 percpu_ref_kill_and_confirm+0x84/0x190 lib/percpu-refcount.c:387
 percpu_ref_kill include/linux/percpu-refcount.h:149 [inline]
 io_ring_ctx_wait_and_kill+0x31/0x370 fs/io_uring.c:8381
 io_uring_release+0x3e/0x50 fs/io_uring.c:8419
 __fput+0x243/0x4d0 fs/file_table.c:281
 ____fput+0x11/0x20 fs/file_table.c:314
 task_work_run+0x8e/0x110 kernel/task_work.c:151
 exit_task_work include/linux/task_work.h:30 [inline]
 do_exit+0x43d/0x1630 kernel/exit.c:809
 do_group_exit+0xc8/0x170 kernel/exit.c:906
 get_signal+0xf9b/0x1510 kernel/signal.c:2758
 arch_do_signal+0x25/0x260 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
 exit_to_user_mode_prepare+0xde/0x170 kernel/entry/common.c:191
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810a7b0c00 of 8 bytes by task 18486 on cpu 1:
 percpu_ref_is_dying include/linux/percpu-refcount.h:352 [inline]
 __io_sq_thread fs/io_uring.c:6700 [inline]
 io_sq_thread+0x50f/0xcd0 fs/io_uring.c:6793
 kthread+0x1fd/0x220 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 18486 Comm: io_uring-sq Not tainted 5.10.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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