Re: [PATCH] staging: greybus: Add missing rwsem around snd_ctl_remove() calls

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On 11/16/21 1:20 AM, Takashi Iwai wrote:
snd_ctl_remove() has to be called with card->controls_rwsem held (when
called after the card instantiation).  This patch adds the missing
rwsem calls around it.

I see the comment above snd_ctl_remove() that says you must hold
the write lock.  And given that, this seems correct to me.

I understand why you want to take the lock just once, rather
than each time snd_ctl_remove() is called.

However I believe the acquisition and release of the lock
belongs inside gbaudio_remove_controls(), not in its caller.

If you disagree, can you please explain why?

Otherwise, will you please submit version two, taking the
lock inside gbaudio_remove_controls()?

Thanks.

					-Alex

Fixes: 510e340efe0c ("staging: greybus: audio: Add helper APIs for dynamic audio modules")
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
  drivers/staging/greybus/audio_helper.c | 8 ++++++--
  1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/greybus/audio_helper.c b/drivers/staging/greybus/audio_helper.c
index 1ed4772d2771..843760675876 100644
--- a/drivers/staging/greybus/audio_helper.c
+++ b/drivers/staging/greybus/audio_helper.c
@@ -192,7 +192,11 @@ int gbaudio_remove_component_controls(struct snd_soc_component *component,
  				      unsigned int num_controls)
  {
  	struct snd_card *card = component->card->snd_card;
+	int err;
- return gbaudio_remove_controls(card, component->dev, controls,
-				       num_controls, component->name_prefix);
+	down_write(&card->controls_rwsem);
+	err = gbaudio_remove_controls(card, component->dev, controls,
+				      num_controls, component->name_prefix);
+	up_write(&card->controls_rwsem);
+	return err;
  }


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