On Wed, 23 Mar 2022 09:08:25 +0100,
Amadeusz SX2awiX4ski wrote:
>
> On 3/22/2022 6:07 PM, Takashi Iwai wrote:
> > Like the previous fixes to hw_params and hw_free ioctl races, we need
> > to paper over the concurrent prepare ioctl calls against hw_params and
> > hw_free, too.
> >
> > This patch implements the locking with the existing
> > runtime->buffer_mutex for prepare ioctls. Unlike the previous case
> > for snd_pcm_hw_hw_params() and snd_pcm_hw_free(), snd_pcm_prepare() is
> > performed to the linked streams, hence the lock can't be applied
> > simply on the top. For tracking the lock in each linked substream, we
> > modify snd_pcm_action_group() slightly and apply the buffer_mutex for
> > the case stream_lock=false (formerly there was no lock applied)
> > there.
> >
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
> > ---
> > sound/core/pcm_native.c | 32 ++++++++++++++++++--------------
> > 1 file changed, 18 insertions(+), 14 deletions(-)
> >
> > diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> > index 266895374b83..0e4fbf5fd87b 100644
> > --- a/sound/core/pcm_native.c
> > +++ b/sound/core/pcm_native.c
> > @@ -1190,15 +1190,17 @@ struct action_ops {
> > static int snd_pcm_action_group(const struct action_ops *ops,
> > struct snd_pcm_substream *substream,
> > snd_pcm_state_t state,
> > - bool do_lock)
> > + bool stream_lock)
> > {
> > struct snd_pcm_substream *s = NULL;
> > struct snd_pcm_substream *s1;
> > int res = 0, depth = 1;
> > snd_pcm_group_for_each_entry(s, substream) {
> > - if (do_lock && s != substream) {
> > - if (s->pcm->nonatomic)
> > + if (s != substream) {
> > + if (!stream_lock)
> > + mutex_lock_nested(&s->runtime->buffer_mutex, depth);
> > + else if (s->pcm->nonatomic)
> > mutex_lock_nested(&s->self_group.mutex, depth);
> > else
> > spin_lock_nested(&s->self_group.lock, depth);
>
> Maybe
> if (!stream_lock)
> mutex_lock_nested(&s->runtime->buffer_mutex, depth);
> else
> snd_pcm_group_lock(&s->self_group, s->pcm->nonatomic);
> ?
No, it must be nested locks with the given subclass. That's why it
has been the open code beforehand, too.
> > @@ -1226,18 +1228,18 @@ static int snd_pcm_action_group(const struct action_ops *ops,
> > ops->post_action(s, state);
> > }
> > _unlock:
> > - if (do_lock) {
> > - /* unlock streams */
> > - snd_pcm_group_for_each_entry(s1, substream) {
> > - if (s1 != substream) {
> > - if (s1->pcm->nonatomic)
> > - mutex_unlock(&s1->self_group.mutex);
> > - else
> > - spin_unlock(&s1->self_group.lock);
> > - }
> > - if (s1 == s) /* end */
> > - break;
> > + /* unlock streams */
> > + snd_pcm_group_for_each_entry(s1, substream) {
> > + if (s1 != substream) {
> > + if (!stream_lock)
> > + mutex_unlock(&s1->runtime->buffer_mutex);
> > + else if (s1->pcm->nonatomic)
> > + mutex_unlock(&s1->self_group.mutex);
> > + else
> > + spin_unlock(&s1->self_group.lock);
>
> And similarly to above, use snd_pcm_group_unlock() here?
This side would be possible to use that macro but it's still better to
have the consistent call pattern.
thanks,
Takashi
