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BUG: KCSAN: data-race in snd_rawmidi_drain_output / snd_rawmidi_transmit

read-write to 0xffff8880639b3878 of 8 bytes by task 3190 on cpu 1:
 __snd_rawmidi_transmit_ack sound/core/rawmidi.c:1267 [inline]
 snd_rawmidi_transmit+0x2b0/0x390 sound/core/rawmidi.c:1326
 snd_vmidi_output_work+0xf1/0x200 sound/core/seq/seq_virmidi.c:144
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2275
 worker_thread+0x635/0xb90 kernel/workqueue.c:2421
 kthread+0x1fd/0x220 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffff8880639b3878 of 8 bytes by task 7310 on cpu 0:
 snd_rawmidi_drain_output+0x12d/0x420 sound/core/rawmidi.c:232
 close_substream+0x13a/0x2c0 sound/core/rawmidi.c:520
 rawmidi_release_priv+0x96/0xf0 sound/core/rawmidi.c:546
 snd_rawmidi_release+0x33/0x80 sound/core/rawmidi.c:577
 __fput+0x24b/0x4e0 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0x8e/0x110 kernel/task_work.c:140
 exit_task_work include/linux/task_work.h:30 [inline]
 do_exit+0x43d/0x1630 kernel/exit.c:823
 do_group_exit+0xc8/0x170 kernel/exit.c:920
 get_signal+0xd5e/0x1440 kernel/signal.c:2770
 arch_do_signal_or_restart+0x2a/0x270 arch/x86/kernel/signal.c:811
 handle_signal_work kernel/entry/common.c:147 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x109/0x1a0 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:302
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7310 Comm: syz-executor.2 Not tainted 5.11.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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