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BUG: KCSAN: data-race in snd_seq_oss_readq_poll / snd_seq_oss_readq_put_event

read to 0xffff8880af007f08 of 4 bytes by task 16193 on cpu 1:
 snd_seq_oss_readq_poll+0x6c/0x90 sound/core/seq/oss/seq_oss_readq.c:209
 snd_seq_oss_poll+0x10c/0x130 sound/core/seq/oss/seq_oss_rw.c:190
 odev_poll+0x4b/0x80 sound/core/seq/oss/seq_oss.c:194
 vfs_poll include/linux/poll.h:90 [inline]
 do_pollfd fs/select.c:859 [inline]
 do_poll fs/select.c:907 [inline]
 do_sys_poll+0x4ac/0x990 fs/select.c:1001
 __do_sys_ppoll fs/select.c:1101 [inline]
 __se_sys_ppoll fs/select.c:1081 [inline]
 __x64_sys_ppoll+0x161/0x1a0 fs/select.c:1081
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8880af007f08 of 4 bytes by task 2501 on cpu 0:
 snd_seq_oss_readq_put_event+0x10c/0x170 sound/core/seq/oss/seq_oss_readq.c:153
 snd_seq_oss_readq_puts+0x97/0xf0 sound/core/seq/oss/seq_oss_readq.c:100
 send_midi_event sound/core/seq/oss/seq_oss_midi.c:608 [inline]
 snd_seq_oss_midi_input+0x1d0/0x4c0 sound/core/seq/oss/seq_oss_midi.c:524
 snd_seq_oss_event_input+0xf9/0x140 sound/core/seq/oss/seq_oss_event.c:429
 snd_seq_deliver_single_event.constprop.0+0x3e8/0x4d0 sound/core/seq/seq_clientmgr.c:638
 deliver_to_subscribers sound/core/seq/seq_clientmgr.c:693 [inline]
 snd_seq_deliver_event+0x1bc/0x4c0 sound/core/seq/seq_clientmgr.c:828
 snd_seq_kernel_client_dispatch+0xef/0x110 sound/core/seq/seq_clientmgr.c:2323
 snd_vmidi_output_work+0x156/0x200 sound/core/seq/seq_virmidi.c:149
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2264
 worker_thread+0xa0/0x800 kernel/workqueue.c:2410
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 2501 Comm: kworker/0:1H Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_highpri snd_vmidi_output_work
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