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BUG: KCSAN: data-race in snd_ctl_notify / snd_ctl_notify

read to 0xffff8882184ae858 of 4 bytes by task 15395 on cpu 0:
 snd_ctl_notify sound/core/control.c:154 [inline]
 snd_ctl_notify+0xd7/0x3b0 sound/core/control.c:141
 loopback_active_notify+0xcb/0xe0 sound/drivers/aloop.c:242
 loopback_trigger+0x59f/0x710 sound/drivers/aloop.c:296
 snd_pcm_do_start sound/core/pcm_native.c:1213 [inline]
 snd_pcm_do_start+0x6d/0x90 sound/core/pcm_native.c:1209
 snd_pcm_action_single+0x5a/0xc0 sound/core/pcm_native.c:1072
 snd_pcm_action+0x83/0x90 sound/core/pcm_native.c:1155
 snd_pcm_start+0x2b/0x40 sound/core/pcm_native.c:1252
 __snd_pcm_lib_xfer+0xd40/0x1176 sound/core/pcm_lib.c:2232
 snd_pcm_oss_write3+0x97/0x180 sound/core/oss/pcm_oss.c:1223
 io_playback_transfer+0x1c0/0x1f0 sound/core/oss/io.c:47
 snd_pcm_plug_write_transfer+0x21b/0x290 sound/core/oss/pcm_plugin.c:620
 snd_pcm_oss_write2+0x157/0x230 sound/core/oss/pcm_oss.c:1352
 snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1418 [inline]
 snd_pcm_oss_write+0x528/0x600 sound/core/oss/pcm_oss.c:2760
 __vfs_write+0x67/0xc0 fs/read_write.c:494
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8882184ae858 of 4 bytes by task 15400 on cpu 1:
 snd_ctl_notify sound/core/control.c:154 [inline]
 snd_ctl_notify+0xe9/0x3b0 sound/core/control.c:141
 loopback_active_notify+0xcb/0xe0 sound/drivers/aloop.c:242
 loopback_trigger+0x59f/0x710 sound/drivers/aloop.c:296
 snd_pcm_do_start sound/core/pcm_native.c:1213 [inline]
 snd_pcm_do_start+0x6d/0x90 sound/core/pcm_native.c:1209
 snd_pcm_action_single+0x5a/0xc0 sound/core/pcm_native.c:1072
 snd_pcm_action+0x83/0x90 sound/core/pcm_native.c:1155
 snd_pcm_start+0x2b/0x40 sound/core/pcm_native.c:1252
 __snd_pcm_lib_xfer+0xd40/0x1176 sound/core/pcm_lib.c:2232
 snd_pcm_oss_write3+0x97/0x180 sound/core/oss/pcm_oss.c:1223
 io_playback_transfer+0x1c0/0x1f0 sound/core/oss/io.c:47
 snd_pcm_plug_write_transfer+0x21b/0x290 sound/core/oss/pcm_plugin.c:620
 snd_pcm_oss_write2+0x157/0x230 sound/core/oss/pcm_oss.c:1352
 snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1418 [inline]
 snd_pcm_oss_write+0x528/0x600 sound/core/oss/pcm_oss.c:2760
 __vfs_write+0x67/0xc0 fs/read_write.c:494
 vfs_write fs/read_write.c:558 [inline]
 vfs_write+0x18a/0x390 fs/read_write.c:542
 ksys_write+0xd5/0x1b0 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x4c/0x60 fs/read_write.c:620
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15400 Comm: syz-executor.5 Not tainted 5.4.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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