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Commit a9edfc60 authored by Karsten Wiese's avatar Karsten Wiese Committed by Jaroslav Kysela
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[ALSA] Handle file operations during snd_card disconnects using static file->f_op 



Alsa used to kmalloc one file->f_op per file per disconnecting snd_card.
This led to oopses sometimes when file->f_op was freed before __fput()
finished.
Patch adds a virtual device for disconnect: VDD.
VDD consists of:
	LIST_HEAD(shutdown_files)
	    protected by DEFINE_SPINLOCK(shutdown_mutex)
	static struct file_operations snd_shutdown_f_ops
	    and functions assigned to it
	Additions to struct snd_monitor_file
	    to specify if instance is hidden by VDD or not.
A VDD's instance is
	created in snd_card_disconnect() under the card->files_lock.
	cleaned up in snd_card_file_remove() under the card->files_lock.

Signed-off-by: default avatarKarsten Wiese <fzu@wemgehoertderstaat.de>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
Signed-off-by: default avatarJaroslav Kysela <perex@suse.cz>
parent 4130d59b

include/sound/core.h

+2 −2
Original line number Diff line number Diff line
@@ -89,10 +89,10 @@ struct snd_device { 
struct snd_monitor_file {

	struct file *file;

	struct snd_monitor_file *next;

	const struct file_operations *disconnected_f_op;

	struct list_head shutdown_list;

};



struct snd_shutdown_f_ops;	/* define it later in init.c */



/* main structure for soundcard */



struct snd_card {

sound/core/init.c

+52 −40
Original line number Diff line number Diff line
@@ -33,10 +33,10 @@ 
#include <sound/control.h>

#include <sound/info.h>



struct snd_shutdown_f_ops {

	struct file_operations f_ops;

	struct snd_shutdown_f_ops *next;

};

static DEFINE_SPINLOCK(shutdown_lock);

static LIST_HEAD(shutdown_files);



static struct file_operations snd_shutdown_f_ops;



static unsigned int snd_cards_lock;	/* locked for registering/using */

struct snd_card *snd_cards[SNDRV_CARDS];
@@ -198,6 +198,25 @@ static ssize_t snd_disconnect_write(struct file *file, const char __user *buf, 
	return -ENODEV;

}



static int snd_disconnect_release(struct inode *inode, struct file *file)

{

	struct snd_monitor_file *df = NULL, *_df;



	spin_lock(&shutdown_lock);

	list_for_each_entry(_df, &shutdown_files, shutdown_list) {

		if (_df->file == file) {

			df = _df;

			break;

		}

	}

	spin_unlock(&shutdown_lock);



	if (likely(df))

		return df->disconnected_f_op->release(inode, file);



	panic("%s(%p, %p) failed!", __FUNCTION__, inode, file);

}



static unsigned int snd_disconnect_poll(struct file * file, poll_table * wait)

{

	return POLLERR | POLLNVAL;
@@ -219,6 +238,22 @@ static int snd_disconnect_fasync(int fd, struct file *file, int on) 
	return -ENODEV;

}



static struct file_operations snd_shutdown_f_ops =

{

	.owner = 	THIS_MODULE,

	.llseek =	snd_disconnect_llseek,

	.read = 	snd_disconnect_read,

	.write =	snd_disconnect_write,

	.release =	snd_disconnect_release,

	.poll =		snd_disconnect_poll,

	.unlocked_ioctl = snd_disconnect_ioctl,

#ifdef CONFIG_COMPAT

	.compat_ioctl = snd_disconnect_ioctl,

#endif

	.mmap =		snd_disconnect_mmap,

	.fasync =	snd_disconnect_fasync

};



/**

 *  snd_card_disconnect - disconnect all APIs from the file-operations (user space)

 *  @card: soundcard structure
@@ -234,9 +269,6 @@ int snd_card_disconnect(struct snd_card *card) 
{

	struct snd_monitor_file *mfile;

	struct file *file;

	struct snd_shutdown_f_ops *s_f_ops;

	struct file_operations *f_ops;

	const struct file_operations *old_f_ops;

	int err;



	spin_lock(&card->files_lock);
@@ -261,34 +293,14 @@ int snd_card_disconnect(struct snd_card *card) 


		/* it's critical part, use endless loop */

		/* we have no room to fail */

		s_f_ops = kmalloc(sizeof(struct snd_shutdown_f_ops), GFP_ATOMIC);

		if (s_f_ops == NULL)

			panic("Atomic allocation failed for snd_shutdown_f_ops!");



		f_ops = &s_f_ops->f_ops;



		memset(f_ops, 0, sizeof(*f_ops));

		f_ops->owner = file->f_op->owner;

		f_ops->release = file->f_op->release;

		f_ops->llseek = snd_disconnect_llseek;

		f_ops->read = snd_disconnect_read;

		f_ops->write = snd_disconnect_write;

		f_ops->poll = snd_disconnect_poll;

		f_ops->unlocked_ioctl = snd_disconnect_ioctl;

#ifdef CONFIG_COMPAT

		f_ops->compat_ioctl = snd_disconnect_ioctl;

#endif

		f_ops->mmap = snd_disconnect_mmap;

		f_ops->fasync = snd_disconnect_fasync;



		s_f_ops->next = card->s_f_ops;

		card->s_f_ops = s_f_ops;

		mfile->disconnected_f_op = mfile->file->f_op;



		f_ops = fops_get(f_ops);

		spin_lock(&shutdown_lock);

		list_add(&mfile->shutdown_list, &shutdown_files);

		spin_unlock(&shutdown_lock);



		old_f_ops = file->f_op;

		file->f_op = f_ops;	/* must be atomic */

		fops_put(old_f_ops);

		fops_get(&snd_shutdown_f_ops);

		mfile->file->f_op = &snd_shutdown_f_ops;

		

		mfile = mfile->next;

	}
@@ -326,8 +338,6 @@ EXPORT_SYMBOL(snd_card_disconnect); 
 */

static int snd_card_do_free(struct snd_card *card)

{

	struct snd_shutdown_f_ops *s_f_ops;



#if defined(CONFIG_SND_MIXER_OSS) || defined(CONFIG_SND_MIXER_OSS_MODULE)

	if (snd_mixer_oss_notify_callback)

		snd_mixer_oss_notify_callback(card, SND_MIXER_OSS_NOTIFY_FREE);
@@ -351,11 +361,6 @@ static int snd_card_do_free(struct snd_card *card) 
		snd_printk(KERN_WARNING "unable to free card info\n");

		/* Not fatal error */

	}

	while (card->s_f_ops) {

		s_f_ops = card->s_f_ops;

		card->s_f_ops = s_f_ops->next;

		kfree(s_f_ops);

	}

	kfree(card);

	return 0;

}
@@ -670,6 +675,7 @@ int snd_card_file_add(struct snd_card *card, struct file *file) 
	if (mfile == NULL)

		return -ENOMEM;

	mfile->file = file;

	mfile->disconnected_f_op = NULL;

	mfile->next = NULL;

	spin_lock(&card->files_lock);

	if (card->shutdown) {
@@ -716,6 +722,12 @@ int snd_card_file_remove(struct snd_card *card, struct file *file) 
		pfile = mfile;

		mfile = mfile->next;

	}

	if (mfile && mfile->disconnected_f_op) {

		fops_put(mfile->disconnected_f_op);

		spin_lock(&shutdown_lock);

		list_del(&mfile->shutdown_list);

		spin_unlock(&shutdown_lock);

	}

	if (card->files == NULL)

		last_close = 1;

	spin_unlock(&card->files_lock);