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BUG: KCSAN: data-race in __snd_rawmidi_transmit_ack / snd_rawmidi_drain_output

read to 0xffff8881240e33f8 of 8 bytes by task 8998 on cpu 0:
 snd_rawmidi_drain_output+0x1e3/0x300 sound/core/rawmidi.c:188
 close_substream.part.0+0x203/0x300 sound/core/rawmidi.c:476
 close_substream sound/core/rawmidi.c:462 [inline]
 rawmidi_release_priv+0x11f/0x180 sound/core/rawmidi.c:502
 snd_rawmidi_release+0x45/0x90 sound/core/rawmidi.c:533
 __fput+0x1e1/0x520 fs/file_table.c:280
 ____fput+0x1f/0x30 fs/file_table.c:313
 task_work_run+0xf6/0x130 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2b4/0x2c0 arch/x86/entry/common.c:163
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
 do_syscall_64+0x353/0x370 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8881240e33f8 of 8 bytes by task 2493 on cpu 1:
 __snd_rawmidi_transmit_ack+0xcf/0x1b0 sound/core/rawmidi.c:1160
 snd_rawmidi_transmit+0x9a/0xd0 sound/core/rawmidi.c:1219
 snd_vmidi_output_work+0xb3/0x200 sound/core/seq/seq_virmidi.c:143
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2269
 worker_thread+0xa0/0x800 kernel/workqueue.c:2415
 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: 1 PID: 2493 Comm: kworker/1:1H Not tainted 5.4.0-rc3+ #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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