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BUG: KCSAN: data-race in io_sq_thread / percpu_ref_kill_and_confirm

write to 0xffff8880b2e69408 of 8 bytes by task 16302 on cpu 1:
 percpu_ref_kill_and_confirm+0x7d/0x1d0 lib/percpu-refcount.c:349
 percpu_ref_kill include/linux/percpu-refcount.h:136 [inline]
 io_ring_ctx_wait_and_kill+0x50/0x3a0 fs/io_uring.c:7291
 io_uring_release+0x47/0x60 fs/io_uring.c:7324
 __fput+0x1e9/0x500 fs/file_table.c:280
 ____fput+0x1b/0x30 fs/file_table.c:313
 task_work_run+0xba/0x120 kernel/task_work.c:123
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2ae/0x2c0 arch/x86/entry/common.c:165
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:279 [inline]
 do_syscall_64+0x38b/0x3b0 arch/x86/entry/common.c:305
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880b2e69408 of 8 bytes by task 16311 on cpu 0:
 io_sq_thread+0x41d/0x7d0 fs/io_uring.c:5966
 kthread+0x203/0x230 kernel/kthread.c:268
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 16311 Comm: io_uring-sq Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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