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BUG: KCSAN: data-race in __io_cqring_fill_event / io_req_defer

write to 0xffff88800a5f0e00 of 4 bytes by task 9815 on cpu 0:
 io_get_cqring fs/io_uring.c:1707 [inline]
 __io_cqring_fill_event+0x135/0x410 fs/io_uring.c:1843
 io_cqring_add_event fs/io_uring.c:1882 [inline]
 __io_req_complete+0xd8/0x1a0 fs/io_uring.c:1926
 io_issue_sqe+0x1fa1/0x3f30 fs/io_uring.c:1206
 io_wq_submit_work+0x24c/0x4a0 fs/io_uring.c:6383
 io_worker_handle_work+0xd08/0x1070 fs/io-wq.c:565
 io_wqe_worker+0x211/0x880 fs/io-wq.c:607
 kthread+0x1fd/0x220 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffff88800a5f0e00 of 4 bytes by task 9810 on cpu 1:
 req_need_defer fs/io_uring.c:1342 [inline]
 io_req_defer+0x3e3/0x580 fs/io_uring.c:6125
 io_queue_sqe+0x23/0x2b0 fs/io_uring.c:6590
 io_submit_sqe+0x2fd/0x5b0 fs/io_uring.c:6684
 io_submit_sqes+0xa66/0x1250 fs/io_uring.c:6932
 __do_sys_io_uring_enter fs/io_uring.c:9326 [inline]
 __se_sys_io_uring_enter+0x21f/0xb70 fs/io_uring.c:9269
 __x64_sys_io_uring_enter+0x74/0x80 fs/io_uring.c:9269
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 9810 Comm: syz-executor.0 Not tainted 5.11.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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