Re: [alsa-devel] [PATCH v2] soundwire: stream: fix bad unlock balance

[Srinivas Kandagatla]

On 06/06/2019 15:28, Pierre-Louis Bossart wrote:
> On 6/6/19 6:22 AM, Srinivas Kandagatla wrote:
> > multi bank switching code takes lock on condition but releases without
> > any check resulting in below warning.
> > This patch fixes this.
>
>
> Question to make sure we are talking about the same thing: multi-link 
> bank switching is a capability beyond the scope of the SoundWire spec 
> which requires hardware support to synchronize links and as Sanyog 
> hinted at in a previous email follow a different flow for bank switches.
>
> You would not use the multi-link mode if you have different links that 
> can operate independently and have no synchronization requirement. You 
> would conversely use the multi-link mode if you have two devices on the 
> same type on different links and want audio to be rendered at the same 
> time.
>
> Can you clarify if indeed you were using the full-blown multi-link mode 
> with hardware synchronization or a regular single-link operation? I am 
> not asking for details of your test hardware, just trying to reconstruct 
> the program flow leading to this problem.

Am testing on a regular single link, which hits this path.

> It could also be that your commit message was meant to say:
> "the msg lock is taken for multi-link cases only but released 
> unconditionally, leading to an unlock balance warning for single-link 
> usages"?
Yes.
Vinod can update comment while applying this patch?
If not I can respin with correct log.

thanks,
srini

> Thanks!
>
> > Â =====================================
> > Â WARNING: bad unlock balance detected!
> > Â 5.1.0-16506-gc1c383a6f0a2-dirty #1523 Tainted: GÂÂÂÂÂÂÂ W
> > Â -------------------------------------
> > Â aplay/2954 is trying to release lock (&bus->msg_lock) at:
> > Â do_bank_switch+0x21c/0x480
> > Â but there are no more locks to release!
> >
> > Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
> > ---
> > Â drivers/soundwire/stream.c | 3 ++-
> > Â 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
> > index ce9cb7fa4724..73c52cd4fec8 100644
> > --- a/drivers/soundwire/stream.c
> > +++ b/drivers/soundwire/stream.c
> > @@ -814,7 +814,8 @@ static int do_bank_switch(struct 
> > sdw_stream_runtime *stream)
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂ goto error;
> > ÂÂÂÂÂÂÂÂÂ }
> > -ÂÂÂÂÂÂÂ mutex_unlock(&bus->msg_lock);
> > +ÂÂÂÂÂÂÂ if (bus->multi_link)
> > +ÂÂÂÂÂÂÂÂÂÂÂ mutex_unlock(&bus->msg_lock);
> > ÂÂÂÂÂ }
> > ÂÂÂÂÂ return ret;