linux-kernel - [PATCH 3.16 048/346] ALSA: ctl: Stop notification after disconnection

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Message-ID: <lsq.1479082460.315653551@decadent.org.uk>
Date:   Mon, 14 Nov 2016 00:14:20 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Takashi Iwai" <tiwai@...e.de>
Subject: [PATCH 3.16 048/346] ALSA: ctl: Stop notification after disconnection

3.16.39-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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

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: Ben Hutchings <ben@...adent.org.uk>
---
 sound/core/control.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -150,6 +150,8 @@ void snd_ctl_notify(struct snd_card *car

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