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ALSA: hda: Avoid racy recreation of widget kobjects

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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>
This commit is contained in:
Takashi Iwai
2017-10-18 15:51:59 +02:00
parent 28d1d6d2f3
commit 9780ded39b
5 changed files with 61 additions and 36 deletions
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2
sound/pci/hda/hda_codec.c
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@@ -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;