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BUG: KCSAN: data-race in snd_rawmidi_drain_output / snd_rawmidi_transmit

write to 0xffff888090774308 of 1 bytes by task 17605 on cpu 1:
 snd_rawmidi_drain_output+0x5b/0x400 sound/core/rawmidi.c:221
 close_substream+0x14c/0x2e0 sound/core/rawmidi.c:510
 rawmidi_release_priv+0x96/0xf0 sound/core/rawmidi.c:536
 snd_rawmidi_release+0x33/0x80 sound/core/rawmidi.c:567
 __fput+0x246/0x4d0 fs/file_table.c:281
 ____fput+0x11/0x20 fs/file_table.c:314
 task_work_run+0x8e/0x110 kernel/task_work.c:141
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:165 [inline]
 exit_to_user_mode_prepare+0x1b2/0x210 kernel/entry/common.c:192
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:267
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888090774308 of 1 bytes by task 3258 on cpu 0:
 __snd_rawmidi_transmit_ack sound/core/rawmidi.c:1258 [inline]
 snd_rawmidi_transmit+0x316/0x410 sound/core/rawmidi.c:1314
 snd_vmidi_output_work+0xf1/0x200 sound/core/seq/seq_virmidi.c:144
 process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x20d/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 3258 Comm: kworker/0:1H Not tainted 5.9.0-rc7-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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