[PATCH 3/5] ALSA: control: Drop async signal support

From: Takashi Iwai <tiwai@suse.de>
To: alsa-devel@alsa-project.org
Subject: [PATCH 3/5] ALSA: control: Drop async signal support
Date: Fri, 15 Jul 2022 12:29:33 +0200	[thread overview]
Message-ID: <20220715102935.4695-4-tiwai@suse.de> (raw)
In-Reply-To: <20220715102935.4695-1-tiwai@suse.de>

The async signal (SIGIO) support for ALSA control API has been never
used by real applications, but yet it can be a cause of various
potential deadlocks (although there hasn't been a bug report in this
code path unlike timer and PCM).  Let's drop the feature as the
simplest solution to align with other APIs.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 include/sound/control.h |  1 -
 sound/core/control.c    | 11 -----------
 2 files changed, 12 deletions(-)

diff --git a/include/sound/control.h b/include/sound/control.h
index fcd3cce673ec..0390d4952dac 100644
--- a/include/sound/control.h
+++ b/include/sound/control.h
@@ -109,7 +109,6 @@ struct snd_ctl_file {
 	int preferred_subdevice[SND_CTL_SUBDEV_ITEMS];
 	wait_queue_head_t change_sleep;
 	spinlock_t read_lock;
-	struct fasync_struct *fasync;
 	int subscribed;			/* read interface is activated */
 	struct list_head events;	/* waiting events for read */
 };
diff --git a/sound/core/control.c b/sound/core/control.c
index 4dba3a342458..3d3b8bf93f80 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -181,7 +181,6 @@ void snd_ctl_notify(struct snd_card *card, unsigned int mask,
 	_found:
 		wake_up(&ctl->change_sleep);
 		spin_unlock(&ctl->read_lock);
-		kill_fasync(&ctl->fasync, SIGIO, POLL_IN);
 	}
 	read_unlock_irqrestore(&card->ctl_files_rwlock, flags);
 }
@@ -2129,14 +2128,6 @@ int snd_ctl_unregister_ioctl_compat(snd_kctl_ioctl_func_t fcn)
 EXPORT_SYMBOL(snd_ctl_unregister_ioctl_compat);
 #endif
 
-static int snd_ctl_fasync(int fd, struct file * file, int on)
-{
-	struct snd_ctl_file *ctl;
-
-	ctl = file->private_data;
-	return fasync_helper(fd, file, on, &ctl->fasync);
-}
-
 /* return the preferred subdevice number if already assigned;
  * otherwise return -1
  */
@@ -2264,7 +2255,6 @@ static const struct file_operations snd_ctl_f_ops =
 	.poll =		snd_ctl_poll,
 	.unlocked_ioctl =	snd_ctl_ioctl,
 	.compat_ioctl =	snd_ctl_ioctl_compat,
-	.fasync =	snd_ctl_fasync,
 };
 
 /*
@@ -2302,7 +2292,6 @@ static int snd_ctl_dev_disconnect(struct snd_device *device)
 	read_lock_irqsave(&card->ctl_files_rwlock, flags);
 	list_for_each_entry(ctl, &card->ctl_files, list) {
 		wake_up(&ctl->change_sleep);
-		kill_fasync(&ctl->fasync, SIGIO, POLL_ERR);
 	}
 	read_unlock_irqrestore(&card->ctl_files_rwlock, flags);
 
-- 
2.35.3

