linux-kernel - [PATCH 3.12 024/100] ALSA: ctl: Stop notification after disconnection

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Date:   Fri, 19 Aug 2016 09:10:23 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Takashi Iwai <tiwai@...e.de>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 024/100] ALSA: ctl: Stop notification after disconnection

From: Takashi Iwai <tiwai@...e.de>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit f388cdcdd160687c6650833f286b9c89c50960ff upstream.

snd_ctl_remove() has a notification for the removal event.  It's
superfluous when done during the device got disconnected.  Although
the notification itself is mostly harmless, it may potentially be
harmful, and should be suppressed.  Actually some components PCM may
free ctl elements during the disconnect or free callbacks, thus it's
no theoretical issue.

This patch adds the check of card->shutdown flag for avoiding
unnecessary notifications after (or during) the disconnect.

Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 sound/core/control.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sound/core/control.c b/sound/core/control.c
index 3fcead61f0ef..251bc575f5c3 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -150,6 +150,8 @@ void snd_ctl_notify(struct snd_card *card, unsigned int mask,

 	if (snd_BUG_ON(!card || !id))
 		return;
+	if (card->shutdown)
+		return;
 	read_lock(&card->ctl_files_rwlock);
 #if defined(CONFIG_SND_MIXER_OSS) || defined(CONFIG_SND_MIXER_OSS_MODULE)
 	card->mixer_oss_change_count++;
-- 
2.9.3