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authorTakashi Iwai <tiwai@suse.de>2017-10-18 15:51:59 +0200
committerTakashi Iwai <tiwai@suse.de>2017-10-19 13:58:36 +0200
commit9780ded39bef5d22a84bdc39112df93f70a58bdd (patch)
tree312c860555df48fda2450d833a2cb1a7a7cd5b0e /sound/hda/hdac_sysfs.c
parent28d1d6d2f314ff395ff67565d1145742614b21c8 (diff)
downloadlinux-9780ded39bef5d22a84bdc39112df93f70a58bdd.tar.bz2
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: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/hda/hdac_sysfs.c')
-rw-r--r--sound/hda/hdac_sysfs.c47
1 files changed, 47 insertions, 0 deletions
diff --git a/sound/hda/hdac_sysfs.c b/sound/hda/hdac_sysfs.c
index 42d61bf41969..e123ba6b2e81 100644
--- a/sound/hda/hdac_sysfs.c
+++ b/sound/hda/hdac_sysfs.c
@@ -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;
+}