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BUG: KCSAN: data-race in snd_seq_oss_readq_poll / snd_seq_oss_readq_put_event

write to 0xffff88810a307488 of 4 bytes by task 2048 on cpu 1:
 snd_seq_oss_readq_put_event+0xfa/0x150 sound/core/seq/oss/seq_oss_readq.c:153
 send_synth_event sound/core/seq/oss/seq_oss_midi.c:586 [inline]
 snd_seq_oss_midi_input+0x4ea/0x500 sound/core/seq/oss/seq_oss_midi.c:522
 snd_seq_oss_event_input+0xbc/0x100 sound/core/seq/oss/seq_oss_event.c:429
 snd_seq_deliver_single_event+0x31e/0x4f0 sound/core/seq/seq_clientmgr.c:637
 deliver_to_subscribers sound/core/seq/seq_clientmgr.c:692 [inline]
 snd_seq_deliver_event+0x38d/0x4a0 sound/core/seq/seq_clientmgr.c:827
 snd_seq_kernel_client_dispatch+0x16f/0x190 sound/core/seq/seq_clientmgr.c:2322
 snd_vmidi_output_work+0x16d/0x200 sound/core/seq/seq_virmidi.c:150
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2275
 worker_thread+0x616/0xa70 kernel/workqueue.c:2421
 kthread+0x20b/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffff88810a307488 of 4 bytes by task 19651 on cpu 0:
 snd_seq_oss_readq_poll+0x5d/0x70 sound/core/seq/oss/seq_oss_readq.c:209
 snd_seq_oss_poll+0x73/0x110 sound/core/seq/oss/seq_oss_rw.c:190
 odev_poll+0x3b/0x50 sound/core/seq/oss/seq_oss.c:203
 vfs_poll include/linux/poll.h:90 [inline]
 do_select+0x8b1/0xfc0 fs/select.c:534
 core_sys_select+0x408/0x690 fs/select.c:677
 do_pselect fs/select.c:759 [inline]
 __do_sys_pselect6+0x1bf/0x220 fs/select.c:800
 __se_sys_pselect6 fs/select.c:791 [inline]
 __x64_sys_pselect6+0x74/0x80 fs/select.c:791
 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: 0 PID: 19651 Comm: syz-executor.3 Not tainted 5.11.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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