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From: Takashi Iwai <tiwai@suse.de>
To: alsa-devel@alsa-project.org
Subject: [PATCH 1/2] ALSA: rawmidi: Drop register_mutex in snd_rawmidi_free()
Date: Tue, 11 Oct 2022 09:01:46 +0200	[thread overview]
Message-ID: <20221011070147.7611-1-tiwai@suse.de> (raw)

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>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/core/rawmidi.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c
index 6963d5a487b3..d8edb6055072 100644
--- a/sound/core/rawmidi.c
+++ b/sound/core/rawmidi.c
@@ -1899,10 +1899,8 @@ 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]);
-- 
2.35.3


             reply	other threads:[~2022-10-11  7:03 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-11  7:01 Takashi Iwai [this message]
2022-10-11  7:01 ` [PATCH 2/2] ALSA: oss: Fix potential deadlock at unregistration Takashi Iwai

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