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ALSA: rawmidi: Drop register_mutex in snd_rawmidi_free()

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commit a70aef7982 upstream.

The register_mutex taken around the dev_unregister callback call in
snd_rawmidi_free() may potentially lead to a mutex deadlock, when OSS
emulation and a hot unplug are involved.

Since the mutex doesn't protect the actual race (as the registration
itself is already protected by another means), let's drop it.

Link: https://lore.kernel.org/r/CAB7eexJP7w1B0mVgDF0dQ+gWor7UdkiwPczmL7pn91xx8xpzOA@mail.gmail.com
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20221011070147.7611-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Takashi Iwai 2022-10-11 09:01:46 +02:00 committed by Greg Kroah-Hartman
parent 45899fae65
commit 550ca3082e
1 changed files with 0 additions and 2 deletions
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2
sound/core/rawmidi.c
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@ -1835,10 +1835,8 @@ static int snd_rawmidi_free(struct snd_rawmidi *rmidi)
snd_info_free_entry(rmidi->proc_entry);
rmidi->proc_entry = NULL;
mutex_lock(&register_mutex);
if (rmidi->ops && rmidi->ops->dev_unregister)
rmidi->ops->dev_unregister(rmidi);
mutex_unlock(&register_mutex);
snd_rawmidi_free_substreams(&rmidi->streams[SNDRV_RAWMIDI_STREAM_INPUT]);
snd_rawmidi_free_substreams(&rmidi->streams[SNDRV_RAWMIDI_STREAM_OUTPUT]);