ALSA: Add a reference counter to card instance

For more strict protection for wild disconnections, a refcount is introduced to the card instance, and let it up/down when an object is referred via snd_lookup_*() in the open ops. The free-after-last-close check is also changed to check this refcount instead of the empty list, too.

Takashi Iwai committed 14 years ago

Commit a0830db1 parent 888ea7d11 files · +86 −32Browse files

Unified · Split

11 files

include/sound/core.h +3 −0
sound/core/compress_offload.c +7 −2
sound/core/control.c +3 −0
sound/core/hwdep.c +4 −1
sound/core/init.c +30 −20
sound/core/oss/mixer_oss.c +8 −2
sound/core/oss/pcm_oss.c +2 −0
sound/core/pcm_native.c +7 −2
sound/core/rawmidi.c +5 −1
sound/core/sound.c +9 −2
sound/core/sound_oss.c +8 −2

include/sound/core.h+3−0

 	int shutdown;			/* this card is going down */
 	int free_on_last_close;		/* free in context of file_release */
 	wait_queue_head_t shutdown_sleep;
+	atomic_t refcount;		/* refcount for disconnection */
 	struct device *dev;		/* device assigned to this card */
 	struct device *card_dev;	/* cardX object for sysfs */
 	const struct file_operations *f_ops;	/* file operations */
 	void *private_data;		/* private data for f_ops->open */
 	struct device *dev;		/* device for sysfs */
+	struct snd_card *card_ptr;	/* assigned card instance */
 };
 /* return a device pointer linked to each sound device as a parent */
 int snd_component_add(struct snd_card *card, const char *component);
 int snd_card_file_add(struct snd_card *card, struct file *file);
 int snd_card_file_remove(struct snd_card *card, struct file *file);
+void snd_card_unref(struct snd_card *card);
 #define snd_card_set_dev(card, devptr) ((card)->dev = (devptr))

sound/core/compress_offload.c+7−2

 	if (dirn != compr->direction) {
 		pr_err("this device doesn't support this direction\n");
+		snd_card_unref(compr->card);
 		return -EINVAL;
 	}
 	data = kzalloc(sizeof(*data), GFP_KERNEL);
-	if (!data)
+	if (!data) {
+		snd_card_unref(compr->card);
 		return -ENOMEM;
+	}
 	data->stream.ops = compr->ops;
 	data->stream.direction = dirn;
 	data->stream.private_data = compr->private_data;
 	runtime = kzalloc(sizeof(*runtime), GFP_KERNEL);
 	if (!runtime) {
 		kfree(data);
+		snd_card_unref(compr->card);
 		return -ENOMEM;
 	}
 	runtime->state = SNDRV_PCM_STATE_OPEN;
 		kfree(runtime);
 		kfree(data);
 	}
-	return ret;
+	snd_card_unref(compr->card);
+	return 0;
 }
 static int snd_compr_free(struct inode *inode, struct file *f)

sound/core/control.c+3−0

 	write_lock_irqsave(&card->ctl_files_rwlock, flags);
 	list_add_tail(&ctl->list, &card->ctl_files);
 	write_unlock_irqrestore(&card->ctl_files_rwlock, flags);
+	snd_card_unref(card);
 	return 0;
       __error:
       __error2:
 	snd_card_file_remove(card, file);
       __error1:
+	if (card)
+		snd_card_unref(card);
       	return err;
 }

sound/core/hwdep.c+4−1

 	if (hw == NULL)
 		return -ENODEV;
-	if (!try_module_get(hw->card->module))
+	if (!try_module_get(hw->card->module)) {
+		snd_card_unref(hw->card);
 		return -EFAULT;
+	}
 	init_waitqueue_entry(&wait, current);
 	add_wait_queue(&hw->open_wait, &wait);
 	mutex_unlock(&hw->open_mutex);
 	if (err < 0)
 		module_put(hw->card->module);
+	snd_card_unref(hw->card);
 	return err;
 }

sound/core/init.c+30−20

 	spin_lock_init(&card->files_lock);
 	INIT_LIST_HEAD(&card->files_list);
 	init_waitqueue_head(&card->shutdown_sleep);
+	atomic_set(&card->refcount, 0);
 #ifdef CONFIG_PM
 	mutex_init(&card->power_lock);
 	init_waitqueue_head(&card->power_sleep);
 	return 0;
 }
+/**
+ * snd_card_unref - release the reference counter
+ * @card: the card instance
+ *
+ * Decrements the reference counter.  When it reaches to zero, wake up
+ * the sleeper and call the destructor if needed.
+ */
+void snd_card_unref(struct snd_card *card)
+{
+	if (atomic_dec_and_test(&card->refcount)) {
+		wake_up(&card->shutdown_sleep);
+		if (card->free_on_last_close)
+			snd_card_do_free(card);
+	}
+}
+EXPORT_SYMBOL(snd_card_unref);
 int snd_card_free_when_closed(struct snd_card *card)
 {
-	int free_now = 0;
+	int ret;
-	int ret = snd_card_disconnect(card);
-	if (ret)
-		return ret;
-	spin_lock(&card->files_lock);
+	atomic_inc(&card->refcount);
-	if (list_empty(&card->files_list))
+	ret = snd_card_disconnect(card);
-		free_now = 1;
+	if (ret) {
-	else
+		atomic_dec(&card->refcount);
-		card->free_on_last_close = 1;
+		return ret;
-	spin_unlock(&card->files_lock);
+	}
-	if (free_now)
+	card->free_on_last_close = 1;
+	if (atomic_dec_and_test(&card->refcount))
 		snd_card_do_free(card);
 	return 0;
 }
 		return ret;
 	/* wait, until all devices are ready for the free operation */
-	wait_event(card->shutdown_sleep, list_empty(&card->files_list));
+	wait_event(card->shutdown_sleep, !atomic_read(&card->refcount));
 	snd_card_do_free(card);
 	return 0;
 }
 		return -ENODEV;
 	}
 	list_add(&mfile->list, &card->files_list);
+	atomic_inc(&card->refcount);
 	spin_unlock(&card->files_lock);
 	return 0;
 }
 int snd_card_file_remove(struct snd_card *card, struct file *file)
 {
 	struct snd_monitor_file *mfile, *found = NULL;
-	int last_close = 0;
 	spin_lock(&card->files_lock);
 	list_for_each_entry(mfile, &card->files_list, list) {
 			break;
 		}
 	}
-	if (list_empty(&card->files_list))
-		last_close = 1;
 	spin_unlock(&card->files_lock);
-	if (last_close) {
-		wake_up(&card->shutdown_sleep);
-		if (card->free_on_last_close)
-			snd_card_do_free(card);
-	}
 	if (!found) {
 		snd_printk(KERN_ERR "ALSA card file remove problem (%p)\n", file);
 		return -ENOENT;
 	}
 	kfree(found);
+	snd_card_unref(card);
 	return 0;
 }

sound/core/oss/mixer_oss.c+8−2

 					 SNDRV_OSS_DEVICE_TYPE_MIXER);
 	if (card == NULL)
 		return -ENODEV;
-	if (card->mixer_oss == NULL)
+	if (card->mixer_oss == NULL) {
+		snd_card_unref(card);
 		return -ENODEV;
+	}
 	err = snd_card_file_add(card, file);
-	if (err < 0)
+	if (err < 0) {
+		snd_card_unref(card);
 		return err;
+	}
 	fmixer = kzalloc(sizeof(*fmixer), GFP_KERNEL);
 	if (fmixer == NULL) {
 		snd_card_file_remove(card, file);
+		snd_card_unref(card);
 		return -ENOMEM;
 	}
 	fmixer->card = card;
 	if (!try_module_get(card->module)) {
 		kfree(fmixer);
 		snd_card_file_remove(card, file);
+		snd_card_unref(card);
 		return -EFAULT;
 	}
 	return 0;

sound/core/oss/pcm_oss.c+2−0

@@ -2457,6 +2457,8 @@ static int snd_pcm_oss_open(struct inode inode, struct file file) · 2456 unmodified lines
2457	__error2:	2457	__error2:
2458	snd_card_file_remove(pcm->card, file);	2458	snd_card_file_remove(pcm->card, file);
2459	__error1:	2459	__error1:
		2460	if (pcm)
		2461	snd_card_unref(pcm->card);
2460	return err;	2462	return err;
2461	}	2463	}
2462		2464

sound/core/pcm_native.c+7−2

 	write_unlock_irq(&snd_pcm_link_rwlock);
 	up_write(&snd_pcm_link_rwsem);
  _nolock:
+	snd_card_unref(substream1->pcm->card);
 	fput_light(file, fput_needed);
 	if (res < 0)
 		kfree(group);
 		return err;
 	pcm = snd_lookup_minor_data(iminor(inode),
 				    SNDRV_DEVICE_TYPE_PCM_PLAYBACK);
-	return snd_pcm_open(file, pcm, SNDRV_PCM_STREAM_PLAYBACK);
+	err = snd_pcm_open(file, pcm, SNDRV_PCM_STREAM_PLAYBACK);
+	snd_card_unref(pcm->card);
+	return err;
 }
 static int snd_pcm_capture_open(struct inode *inode, struct file *file)
 		return err;
 	pcm = snd_lookup_minor_data(iminor(inode),
 				    SNDRV_DEVICE_TYPE_PCM_CAPTURE);
-	return snd_pcm_open(file, pcm, SNDRV_PCM_STREAM_CAPTURE);
+	err = snd_pcm_open(file, pcm, SNDRV_PCM_STREAM_CAPTURE);
+	snd_card_unref(pcm->card);
+	return err;
 }
 static int snd_pcm_open(struct file *file, struct snd_pcm *pcm, int stream)

sound/core/rawmidi.c+5−1

 	if (rmidi == NULL)
 		return -ENODEV;
-	if (!try_module_get(rmidi->card->module))
+	if (!try_module_get(rmidi->card->module)) {
+		snd_card_unref(rmidi->card);
 		return -ENXIO;
+	}
 	mutex_lock(&rmidi->open_mutex);
 	card = rmidi->card;
 #endif
 	file->private_data = rawmidi_file;
 	mutex_unlock(&rmidi->open_mutex);
+	snd_card_unref(rmidi->card);
 	return 0;
  __error:
  __error_card:
 	mutex_unlock(&rmidi->open_mutex);
 	module_put(rmidi->card->module);
+	snd_card_unref(rmidi->card);
 	return err;
 }

sound/core/sound.c+9−2

  *
  * Checks that a minor device with the specified type is registered, and returns
  * its user data pointer.
+ *
+ * This function increments the reference counter of the card instance
+ * if an associated instance with the given minor number and type is found.
+ * The caller must call snd_card_unref() appropriately later.
  */
 void *snd_lookup_minor_data(unsigned int minor, int type)
 {
 		return NULL;
 	mutex_lock(&sound_mutex);
 	mreg = snd_minors[minor];
-	if (mreg && mreg->type == type)
+	if (mreg && mreg->type == type) {
 		private_data = mreg->private_data;
-	else
+		if (mreg->card_ptr)
+			atomic_inc(&mreg->card_ptr->refcount);
+	} else
 		private_data = NULL;
 	mutex_unlock(&sound_mutex);
 	return private_data;
 	preg->device = dev;
 	preg->f_ops = f_ops;
 	preg->private_data = private_data;
+	preg->card_ptr = card;
 	mutex_lock(&sound_mutex);
 #ifdef CONFIG_SND_DYNAMIC_MINORS
 	minor = snd_find_free_minor(type);

sound/core/sound_oss.c+8−2

 static struct snd_minor *snd_oss_minors[SNDRV_OSS_MINORS];
 static DEFINE_MUTEX(sound_oss_mutex);
+/* NOTE: This function increments the refcount of the associated card like
+ * snd_lookup_minor_data(); the caller must call snd_card_unref() appropriately
+ */
 void *snd_lookup_oss_minor_data(unsigned int minor, int type)
 {
 	struct snd_minor *mreg;
 		return NULL;
 	mutex_lock(&sound_oss_mutex);
 	mreg = snd_oss_minors[minor];
-	if (mreg && mreg->type == type)
+	if (mreg && mreg->type == type) {
 		private_data = mreg->private_data;
-	else
+		if (mreg->card_ptr)
+			atomic_inc(&mreg->card_ptr->refcount);
+	} else
 		private_data = NULL;
 	mutex_unlock(&sound_oss_mutex);
 	return private_data;
 	preg->device = dev;
 	preg->f_ops = f_ops;
 	preg->private_data = private_data;
+	preg->card_ptr = card;
 	mutex_lock(&sound_oss_mutex);
 	snd_oss_minors[minor] = preg;
 	minor_unit = SNDRV_MINOR_OSS_DEVICE(minor);