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Commit 9780ded3 authored by Takashi Iwai's avatar Takashi Iwai
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ALSA: hda: Avoid racy recreation of widget kobjects 

The refresh of HD-audio widget sysfs kobjects via
snd_hdac_refresh_widget_sysfs() is slightly racy.
The driver recreates the whole tree from scratch after deleting the
whole.  When CONFIG_DEBUG_KOBJECT_RELEASE option is used, kobject
release doesn't happen immediately but delayed, while the re-creation
of the same named kobject happens soon after invoking kobject_put().
This may end up with the conflicts of duplicated kobjects, as found in
the bug report below.

In this patch, we take another approach to refresh the tree: instead
of recreating the whole tree, just add the new nodes and delete the
non-existing nodes.  Since the refresh happens only once at
initialization, no longer race would happen.

Along with the code change, merge snd_hdac_refresh_widget_sysfs() with
the existing snd_hdac_refresh_widgets() with an additional bool flag
for simplifying the code.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=197307


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 28d1d6d2

include/sound/hdaudio.h

+1 −2
Original line number Diff line number Diff line
@@ -111,8 +111,7 @@ void snd_hdac_device_unregister(struct hdac_device *codec); 
int snd_hdac_device_set_chip_name(struct hdac_device *codec, const char *name);

int snd_hdac_codec_modalias(struct hdac_device *hdac, char *buf, size_t size);



int snd_hdac_refresh_widgets(struct hdac_device *codec);

int snd_hdac_refresh_widget_sysfs(struct hdac_device *codec);

int snd_hdac_refresh_widgets(struct hdac_device *codec, bool sysfs);



unsigned int snd_hdac_make_cmd(struct hdac_device *codec, hda_nid_t nid,

			       unsigned int verb, unsigned int parm);

sound/hda/hdac_device.c

+10 −33
Original line number Diff line number Diff line
@@ -87,7 +87,7 @@ int snd_hdac_device_init(struct hdac_device *codec, struct hdac_bus *bus, 


	fg = codec->afg ? codec->afg : codec->mfg;



	err = snd_hdac_refresh_widgets(codec);

	err = snd_hdac_refresh_widgets(codec, false);

	if (err < 0)

		goto error;
@@ -388,11 +388,12 @@ static void setup_fg_nodes(struct hdac_device *codec) 
/**

 * snd_hdac_refresh_widgets - Reset the widget start/end nodes

 * @codec: the codec object

 * @sysfs: re-initialize sysfs tree, too

 */

int snd_hdac_refresh_widgets(struct hdac_device *codec)

int snd_hdac_refresh_widgets(struct hdac_device *codec, bool sysfs)

{

	hda_nid_t start_nid;

	int nums;

	int nums, err;



	nums = snd_hdac_get_sub_nodes(codec, codec->afg, &start_nid);

	if (!start_nid || nums <= 0 || nums >= 0xff) {
@@ -401,6 +402,12 @@ int snd_hdac_refresh_widgets(struct hdac_device *codec) 
		return -EINVAL;

	}



	if (sysfs) {

		err = hda_widget_sysfs_reinit(codec, start_nid, nums);

		if (err < 0)

			return err;

	}



	codec->num_nodes = nums;

	codec->start_nid = start_nid;

	codec->end_nid = start_nid + nums;
@@ -408,36 +415,6 @@ int snd_hdac_refresh_widgets(struct hdac_device *codec) 
}

EXPORT_SYMBOL_GPL(snd_hdac_refresh_widgets);



/**

 * snd_hdac_refresh_widget_sysfs - Reset the codec widgets and reinit the

 * codec sysfs

 * @codec: the codec object

 *

 * first we need to remove sysfs, then refresh widgets and lastly

 * recreate it

 */

int snd_hdac_refresh_widget_sysfs(struct hdac_device *codec)

{

	int ret;



	if (device_is_registered(&codec->dev))

		hda_widget_sysfs_exit(codec);

	ret = snd_hdac_refresh_widgets(codec);

	if (ret) {

		dev_err(&codec->dev, "failed to refresh widget: %d\n", ret);

		return ret;

	}

	if (device_is_registered(&codec->dev)) {

		ret = hda_widget_sysfs_init(codec);

		if (ret) {

			dev_err(&codec->dev, "failed to init sysfs: %d\n", ret);

			return ret;

		}

	}

	return ret;

}

EXPORT_SYMBOL_GPL(snd_hdac_refresh_widget_sysfs);



/* return CONNLIST_LEN parameter of the given widget */

static unsigned int get_num_conns(struct hdac_device *codec, hda_nid_t nid)

{

sound/hda/hdac_sysfs.c

+47 −0
Original line number Diff line number Diff line
@@ -414,3 +414,50 @@ void hda_widget_sysfs_exit(struct hdac_device *codec) 
{

	widget_tree_free(codec);

}



int hda_widget_sysfs_reinit(struct hdac_device *codec,

			    hda_nid_t start_nid, int num_nodes)

{

	struct hdac_widget_tree *tree;

	hda_nid_t end_nid = start_nid + num_nodes;

	hda_nid_t nid;

	int i;



	if (!codec->widgets)

		return hda_widget_sysfs_init(codec);



	tree = kmemdup(codec->widgets, sizeof(*tree), GFP_KERNEL);

	if (!tree)

		return -ENOMEM;



	tree->nodes = kcalloc(num_nodes + 1, sizeof(*tree->nodes), GFP_KERNEL);

	if (!tree->nodes) {

		kfree(tree);

		return -ENOMEM;

	}



	/* prune non-existing nodes */

	for (i = 0, nid = codec->start_nid; i < codec->num_nodes; i++, nid++) {

		if (nid < start_nid || nid >= end_nid)

			free_widget_node(codec->widgets->nodes[i],

					 &widget_node_group);

	}



	/* add new nodes */

	for (i = 0, nid = start_nid; i < num_nodes; i++, nid++) {

		if (nid < codec->start_nid || nid >= codec->end_nid)

			add_widget_node(tree->root, nid, &widget_node_group,

					&tree->nodes[i]);

		else

			tree->nodes[i] =

				codec->widgets->nodes[nid - codec->start_nid];

	}



	/* replace with the new tree */

	kfree(codec->widgets->nodes);

	kfree(codec->widgets);

	codec->widgets = tree;



	kobject_uevent(tree->root, KOBJ_CHANGE);

	return 0;

}

sound/hda/local.h

+2 −0
Original line number Diff line number Diff line
@@ -28,6 +28,8 @@ static inline unsigned int get_wcaps_channels(u32 wcaps) 


extern const struct attribute_group *hdac_dev_attr_groups[];

int hda_widget_sysfs_init(struct hdac_device *codec);

int hda_widget_sysfs_reinit(struct hdac_device *codec, hda_nid_t start_nid,

			    int num_nodes);

void hda_widget_sysfs_exit(struct hdac_device *codec);



#endif /* __HDAC_LOCAL_H */

sound/pci/hda/hda_codec.c

+1 −1
Original line number Diff line number Diff line
@@ -977,7 +977,7 @@ int snd_hda_codec_update_widgets(struct hda_codec *codec) 
	hda_nid_t fg;

	int err;



	err = snd_hdac_refresh_widget_sysfs(&codec->core);

	err = snd_hdac_refresh_widgets(&codec->core, true);

	if (err < 0)

		return err;