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SubjectRe: [greybus-dev] [PATCH] staging: greybus: Add missing rwsem around snd_ctl_remove() calls
On Wed, 17 Nov 2021 20:56:14 +0100,
Alex Elder wrote:
>
> 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?

In general if the function returns an error and has a loop inside,
taking a lock in the caller side avoids the forgotten unlock.


Takashi


> 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@suse.de>
> > ---
> > 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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