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| author |   Takashi Iwai <tiwai@suse.de> | 2022-09-10 16:25:50 +0200 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2022-09-10 16:26:19 +0200 |
| commit | ead3d3c5b54f76da79c079e61bacb4279ec56965 (patch) | |
| tree | e92e5050c3bd274c2a837e3aebd3a8a83b4b2d8a /sound/pci/hda/hda_bind.c | |
| parent | Merge tag 'asoc-fix-v6.0-rc4' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus (diff) | |
| download | linux-dev-ead3d3c5b54f76da79c079e61bacb4279ec56965.tar.xz linux-dev-ead3d3c5b54f76da79c079e61bacb4279ec56965.zip | |
ALSA: hda: Fix hang at HD-audio codec unbinding due to refcount saturation
We fixed the potential deadlock at dynamic unbinding the HD-audio
codec at the commit 7206998f578d ("ALSA: hda: Fix potential deadlock
at codec unbinding"), but ironically, this caused another potential
deadlock. The current code uses refcount_dec() and waits for the
pending task with wait_event for dropping the refcount to 0. This
works fine when PCMs are assigned and actually waiting for the
refcount drop.
Meanwhile, when there was no PCM assigned, the refcount_dec() call
itself was supposed to drop to zero -- alas, it doesn't in reality;
refcount_dec() complains, spews kernel warning and it saturates
instead of dropping to 0, due to the nature of refcount_dec()
implementation. This eventually blocks the wait_event() wakeup and
the code get stuck there.
For avoiding the problem, we call refcount_dec_and_test() and skips
the sync-wait if it already reaches to zero.
The patch does a slight code reshuffling to make sure to invoke other
disconnect calls before the sync-wait, too.
Fixes: 7206998f578d ("ALSA: hda: Fix potential deadlock at codec unbinding")
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/YxtflWQnslMHVlU7@intel.com
Link: https://lore.kernel.org/r/20220910142550.28494-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/pci/hda/hda_bind.c')
| -rw-r--r-- | sound/pci/hda/hda_bind.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/sound/pci/hda/hda_bind.c b/sound/pci/hda/hda_bind.c index cae9a975cbcc..1a868dd9dc4b 100644 --- a/sound/pci/hda/hda_bind.c +++ b/sound/pci/hda/hda_bind.c @@ -157,10 +157,10 @@ static int hda_codec_driver_remove(struct device *dev) return codec->bus->core.ext_ops->hdev_detach(&codec->core); } - refcount_dec(&codec->pcm_ref); snd_hda_codec_disconnect_pcms(codec); snd_hda_jack_tbl_disconnect(codec); - wait_event(codec->remove_sleep, !refcount_read(&codec->pcm_ref)); + if (!refcount_dec_and_test(&codec->pcm_ref)) + wait_event(codec->remove_sleep, !refcount_read(&codec->pcm_ref)); snd_power_sync_ref(codec->bus->card); if (codec->patch_ops.free) |