diff mbox series

soundwire: stream: fix bad unlock balance

Message ID 20190522162528.5892-1-srinivas.kandagatla@linaro.org (mailing list archive)
State New, archived
Headers show
Series soundwire: stream: fix bad unlock balance | expand

Commit Message

Srinivas Kandagatla May 22, 2019, 4:25 p.m. UTC
This patch fixes below warning due to unlocking without locking.

 =====================================
 WARNING: bad unlock balance detected!
 5.1.0-16506-gc1c383a6f0a2-dirty #1523 Tainted: G        W
 -------------------------------------
 aplay/2954 is trying to release lock (&bus->msg_lock) at:
 do_bank_switch+0x21c/0x480
 but there are no more locks to release!

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
---
 drivers/soundwire/stream.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Pierre-Louis Bossart May 22, 2019, 4:41 p.m. UTC | #1
On 5/22/19 11:25 AM, Srinivas Kandagatla wrote:
> This patch fixes below warning due to unlocking without locking.
> 
>   =====================================
>   WARNING: bad unlock balance detected!
>   5.1.0-16506-gc1c383a6f0a2-dirty #1523 Tainted: G        W
>   -------------------------------------
>   aplay/2954 is trying to release lock (&bus->msg_lock) at:
>   do_bank_switch+0x21c/0x480
>   but there are no more locks to release!
> 
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> ---
>   drivers/soundwire/stream.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
> index 544925ff0b40..d16268f30e4f 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)
>   			goto error;
>   		}
>   
> -		mutex_unlock(&bus->msg_lock);
> +		if (mutex_is_locked(&bus->msg_lock))
> +			utex_unlock(&bus->msg_lock);

Does this even compile? should be mutex_unlock, no?

We also may want to identify the issue in more details without pushing 
it under the rug. The locking mechanism is far from simple and it's 
likely there are a number of problems with it.

>   	}
>   
>   	return ret;
>
Srinivas Kandagatla May 22, 2019, 4:41 p.m. UTC | #2
On 22/05/2019 17:25, Srinivas Kandagatla wrote:
> This patch fixes below warning due to unlocking without locking.
> 
>   =====================================
>   WARNING: bad unlock balance detected!
>   5.1.0-16506-gc1c383a6f0a2-dirty #1523 Tainted: G        W
>   -------------------------------------
>   aplay/2954 is trying to release lock (&bus->msg_lock) at:
>   do_bank_switch+0x21c/0x480
>   but there are no more locks to release!
> 
> Signed-off-by: Srinivas Kandagatla<srinivas.kandagatla@linaro.org>
> ---
>   drivers/soundwire/stream.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
> index 544925ff0b40..d16268f30e4f 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)
>   			goto error;
>   		}
>   
> -		mutex_unlock(&bus->msg_lock);
> +		if (mutex_is_locked(&bus->msg_lock))
> +			utex_unlock(&bus->msg_lock);
Looks like I messed this up!

I will resend this one!

--srini
>   	}
Srinivas Kandagatla May 23, 2019, 8:43 a.m. UTC | #3
On 22/05/2019 17:41, Pierre-Louis Bossart wrote:
> 
> 
> On 5/22/19 11:25 AM, Srinivas Kandagatla wrote:
>> This patch fixes below warning due to unlocking without locking.
>>
>>   =====================================
>>   WARNING: bad unlock balance detected!
>>   5.1.0-16506-gc1c383a6f0a2-dirty #1523 Tainted: G        W
>>   -------------------------------------
>>   aplay/2954 is trying to release lock (&bus->msg_lock) at:
>>   do_bank_switch+0x21c/0x480
>>   but there are no more locks to release!
>>
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>> ---
>>   drivers/soundwire/stream.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
>> index 544925ff0b40..d16268f30e4f 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)
>>               goto error;
>>           }
>> -        mutex_unlock(&bus->msg_lock);
>> +        if (mutex_is_locked(&bus->msg_lock))
>> +            utex_unlock(&bus->msg_lock);
> 
> Does this even compile? should be mutex_unlock, no?
> 
> We also may want to identify the issue in more details without pushing 
> it under the rug. The locking mechanism is far from simple and it's 
> likely there are a number of problems with it.
> 
msg_lock is taken conditionally during multi link bank switch cases, 
however the unlock is done unconditionally leading to this warning.

Having a closer look show that there could be a dead lock in this path 
while executing sdw_transfer(). And infact there is no need to take 
msg_lock in  multi link switch cases as sdw_transfer should take care of 
this.

Vinod/Sanyog any reason why msg_lock is really required in this path?

--srini

>>       }
>>       return ret;
>>
Sanyog Kale May 23, 2019, 9:20 a.m. UTC | #4
On Thu, May 23, 2019 at 09:43:14AM +0100, Srinivas Kandagatla wrote:
> 
> 
> On 22/05/2019 17:41, Pierre-Louis Bossart wrote:
> > 
> > 
> > On 5/22/19 11:25 AM, Srinivas Kandagatla wrote:
> > > This patch fixes below warning due to unlocking without locking.
> > > 
> > > ?? =====================================
> > > ?? WARNING: bad unlock balance detected!
> > > ?? 5.1.0-16506-gc1c383a6f0a2-dirty #1523 Tainted: G?????????????? W
> > > ?? -------------------------------------
> > > ?? aplay/2954 is trying to release lock (&bus->msg_lock) at:
> > > ?? do_bank_switch+0x21c/0x480
> > > ?? but there are no more locks to release!
> > > 
> > > Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> > > ---
> > > ?? drivers/soundwire/stream.c | 3 ++-
> > > ?? 1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
> > > index 544925ff0b40..d16268f30e4f 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)
> > > ?????????????????????????? goto error;
> > > ?????????????????? }
> > > -?????????????? mutex_unlock(&bus->msg_lock);
> > > +?????????????? if (mutex_is_locked(&bus->msg_lock))
> > > +?????????????????????? utex_unlock(&bus->msg_lock);
> > 
> > Does this even compile? should be mutex_unlock, no?
> > 
> > We also may want to identify the issue in more details without pushing
> > it under the rug. The locking mechanism is far from simple and it's
> > likely there are a number of problems with it.
> > 
> msg_lock is taken conditionally during multi link bank switch cases, however
> the unlock is done unconditionally leading to this warning.
> 
> Having a closer look show that there could be a dead lock in this path while
> executing sdw_transfer(). And infact there is no need to take msg_lock in
> multi link switch cases as sdw_transfer should take care of this.
> 
> Vinod/Sanyog any reason why msg_lock is really required in this path?
>

In case of multi link we use sdw_transfer_defer instead of sdw_transfer
where lock is not acquired, hence lock is acquired in do_bank_switch for
multi link. we should add same check of multi link to release lock in
do_bank_switch.

> --srini
> 
> > > ?????????? }
> > > ?????????? return ret;
> > >
Srinivas Kandagatla May 23, 2019, 9:30 a.m. UTC | #5
On 23/05/2019 10:20, Sanyog Kale wrote:
> On Thu, May 23, 2019 at 09:43:14AM +0100, Srinivas Kandagatla wrote:
>>
>>
>> On 22/05/2019 17:41, Pierre-Louis Bossart wrote:
>>>
>>>
>>> On 5/22/19 11:25 AM, Srinivas Kandagatla wrote:
>>>> This patch fixes below warning due to unlocking without locking.
>>>>
>>>> ?? =====================================
>>>> ?? WARNING: bad unlock balance detected!
>>>> ?? 5.1.0-16506-gc1c383a6f0a2-dirty #1523 Tainted: G?????????????? W
>>>> ?? -------------------------------------
>>>> ?? aplay/2954 is trying to release lock (&bus->msg_lock) at:
>>>> ?? do_bank_switch+0x21c/0x480
>>>> ?? but there are no more locks to release!
>>>>
>>>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>>>> ---
>>>> ?? drivers/soundwire/stream.c | 3 ++-
>>>> ?? 1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
>>>> index 544925ff0b40..d16268f30e4f 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)
>>>> ?????????????????????????? goto error;
>>>> ?????????????????? }
>>>> -?????????????? mutex_unlock(&bus->msg_lock);
>>>> +?????????????? if (mutex_is_locked(&bus->msg_lock))
>>>> +?????????????????????? utex_unlock(&bus->msg_lock);
>>>
>>> Does this even compile? should be mutex_unlock, no?
>>>
>>> We also may want to identify the issue in more details without pushing
>>> it under the rug. The locking mechanism is far from simple and it's
>>> likely there are a number of problems with it.
>>>
>> msg_lock is taken conditionally during multi link bank switch cases, however
>> the unlock is done unconditionally leading to this warning.
>>
>> Having a closer look show that there could be a dead lock in this path while
>> executing sdw_transfer(). And infact there is no need to take msg_lock in
>> multi link switch cases as sdw_transfer should take care of this.
>>
>> Vinod/Sanyog any reason why msg_lock is really required in this path?
>>
> 
> In case of multi link we use sdw_transfer_defer instead of sdw_transfer
> where lock is not acquired, hence lock is acquired in do_bank_switch for
> multi link. we should add same check of multi link to release lock in
> do_bank_switch.

probably we should just add the lock around the sdw_transfer_defer call 
in sdw_bank_switch()?
This should cleanup the code a bit too.

something like:

------------------------------------>cut<-----------------------------
diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
index d01060dbee96..f455af5b8151 100644
--- a/drivers/soundwire/stream.c
+++ b/drivers/soundwire/stream.c
@@ -676,10 +676,13 @@ static int sdw_bank_switch(struct sdw_bus *bus, 
int m_rt_count)
          */
         multi_link = bus->multi_link && (m_rt_count > 1);

-       if (multi_link)
+       if (multi_link) {
+               mutex_lock(&bus->msg_lock);
                 ret = sdw_transfer_defer(bus, wr_msg, &bus->defer_msg);
-       else
+               mutex_unlock(&bus->msg_lock);
+       } else {
                 ret = sdw_transfer(bus, wr_msg);
+       }

         if (ret < 0) {
                 dev_err(bus->dev, "Slave frame_ctrl reg write failed\n");
@@ -742,25 +745,19 @@ static int do_bank_switch(struct 
sdw_stream_runtime *stream)
         struct sdw_master_runtime *m_rt = NULL;
         const struct sdw_master_ops *ops;
         struct sdw_bus *bus = NULL;
-       bool multi_link = false;
         int ret = 0;

         list_for_each_entry(m_rt, &stream->master_list, stream_node) {
                 bus = m_rt->bus;
                 ops = bus->ops;

-               if (bus->multi_link) {
-                       multi_link = true;
-                       mutex_lock(&bus->msg_lock);
-               }
-
                 /* Pre-bank switch */
                 if (ops->pre_bank_switch) {
                         ret = ops->pre_bank_switch(bus);
                         if (ret < 0) {
                                 dev_err(bus->dev,
                                         "Pre bank switch op failed: 
%d\n", ret);
-                               goto msg_unlock;
+                               return ret;
                         }
                 }

@@ -814,7 +811,6 @@ static int do_bank_switch(struct sdw_stream_runtime 
*stream)
                         goto error;
                 }

-               mutex_unlock(&bus->msg_lock);
         }

         return ret;
@@ -827,16 +823,6 @@ static int do_bank_switch(struct sdw_stream_runtime 
*stream)
                 kfree(bus->defer_msg.msg);
         }

-msg_unlock:
-
-       if (multi_link) {
-               list_for_each_entry(m_rt, &stream->master_list, 
stream_node) {
-                       bus = m_rt->bus;
-                       if (mutex_is_locked(&bus->msg_lock))
-                               mutex_unlock(&bus->msg_lock);
-               }
-       }
-
         return ret;
  }

------------------------------------>cut<-----------------------------
> 
>> --srini
>>
>>>> ?????????? }
>>>> ?????????? return ret;
>>>>
>
Sanyog Kale May 23, 2019, 9:41 a.m. UTC | #6
On Thu, May 23, 2019 at 10:30:20AM +0100, Srinivas Kandagatla wrote:
> 
> 
> On 23/05/2019 10:20, Sanyog Kale wrote:
> > On Thu, May 23, 2019 at 09:43:14AM +0100, Srinivas Kandagatla wrote:
> > > 
> > > 
> > > On 22/05/2019 17:41, Pierre-Louis Bossart wrote:
> > > > 
> > > > 
> > > > On 5/22/19 11:25 AM, Srinivas Kandagatla wrote:
> > > > > This patch fixes below warning due to unlocking without locking.
> > > > > 
> > > > > ?? =====================================
> > > > > ?? WARNING: bad unlock balance detected!
> > > > > ?? 5.1.0-16506-gc1c383a6f0a2-dirty #1523 Tainted: G?????????????? W
> > > > > ?? -------------------------------------
> > > > > ?? aplay/2954 is trying to release lock (&bus->msg_lock) at:
> > > > > ?? do_bank_switch+0x21c/0x480
> > > > > ?? but there are no more locks to release!
> > > > > 
> > > > > Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> > > > > ---
> > > > > ?? drivers/soundwire/stream.c | 3 ++-
> > > > > ?? 1 file changed, 2 insertions(+), 1 deletion(-)
> > > > > 
> > > > > diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
> > > > > index 544925ff0b40..d16268f30e4f 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)
> > > > > ?????????????????????????? goto error;
> > > > > ?????????????????? }
> > > > > -?????????????? mutex_unlock(&bus->msg_lock);
> > > > > +?????????????? if (mutex_is_locked(&bus->msg_lock))
> > > > > +?????????????????????? utex_unlock(&bus->msg_lock);
> > > > 
> > > > Does this even compile? should be mutex_unlock, no?
> > > > 
> > > > We also may want to identify the issue in more details without pushing
> > > > it under the rug. The locking mechanism is far from simple and it's
> > > > likely there are a number of problems with it.
> > > > 
> > > msg_lock is taken conditionally during multi link bank switch cases, however
> > > the unlock is done unconditionally leading to this warning.
> > > 
> > > Having a closer look show that there could be a dead lock in this path while
> > > executing sdw_transfer(). And infact there is no need to take msg_lock in
> > > multi link switch cases as sdw_transfer should take care of this.
> > > 
> > > Vinod/Sanyog any reason why msg_lock is really required in this path?
> > > 
> > 
> > In case of multi link we use sdw_transfer_defer instead of sdw_transfer
> > where lock is not acquired, hence lock is acquired in do_bank_switch for
> > multi link. we should add same check of multi link to release lock in
> > do_bank_switch.
> 
> probably we should just add the lock around the sdw_transfer_defer call in
> sdw_bank_switch()?
> This should cleanup the code a bit too.
> 
> something like:
> 
> ------------------------------------>cut<-----------------------------
> diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
> index d01060dbee96..f455af5b8151 100644
> --- a/drivers/soundwire/stream.c
> +++ b/drivers/soundwire/stream.c
> @@ -676,10 +676,13 @@ static int sdw_bank_switch(struct sdw_bus *bus, int
> m_rt_count)
>          */
>         multi_link = bus->multi_link && (m_rt_count > 1);
> 
> -       if (multi_link)
> +       if (multi_link) {
> +               mutex_lock(&bus->msg_lock);
>                 ret = sdw_transfer_defer(bus, wr_msg, &bus->defer_msg);
> -       else
> +               mutex_unlock(&bus->msg_lock);

you cant release bus_lock here since message is not yet transferred.
we can only release bus_lock after sdw_ml_sync_bank_switch function where
we confirm that message transfer is completed.

> +       } else {
>                 ret = sdw_transfer(bus, wr_msg);
> +       }
> 
>         if (ret < 0) {
>                 dev_err(bus->dev, "Slave frame_ctrl reg write failed\n");
> @@ -742,25 +745,19 @@ static int do_bank_switch(struct sdw_stream_runtime
> *stream)
>         struct sdw_master_runtime *m_rt = NULL;
>         const struct sdw_master_ops *ops;
>         struct sdw_bus *bus = NULL;
> -       bool multi_link = false;
>         int ret = 0;
> 
>         list_for_each_entry(m_rt, &stream->master_list, stream_node) {
>                 bus = m_rt->bus;
>                 ops = bus->ops;
> 
> -               if (bus->multi_link) {
> -                       multi_link = true;
> -                       mutex_lock(&bus->msg_lock);
> -               }
> -
>                 /* Pre-bank switch */
>                 if (ops->pre_bank_switch) {
>                         ret = ops->pre_bank_switch(bus);
>                         if (ret < 0) {
>                                 dev_err(bus->dev,
>                                         "Pre bank switch op failed: %d\n",
> ret);
> -                               goto msg_unlock;
> +                               return ret;
>                         }
>                 }
> 
> @@ -814,7 +811,6 @@ static int do_bank_switch(struct sdw_stream_runtime
> *stream)
>                         goto error;
>                 }
> 
> -               mutex_unlock(&bus->msg_lock);
>         }
> 
>         return ret;
> @@ -827,16 +823,6 @@ static int do_bank_switch(struct sdw_stream_runtime
> *stream)
>                 kfree(bus->defer_msg.msg);
>         }
> 
> -msg_unlock:
> -
> -       if (multi_link) {
> -               list_for_each_entry(m_rt, &stream->master_list, stream_node)
> {
> -                       bus = m_rt->bus;
> -                       if (mutex_is_locked(&bus->msg_lock))
> -                               mutex_unlock(&bus->msg_lock);
> -               }
> -       }
> -
>         return ret;
>  }
> 
> ------------------------------------>cut<-----------------------------
> > 
> > > --srini
> > > 
> > > > > ?????????? }
> > > > > ?????????? return ret;
> > > > > 
> >
diff mbox series

Patch

diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c
index 544925ff0b40..d16268f30e4f 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)
 			goto error;
 		}
 
-		mutex_unlock(&bus->msg_lock);
+		if (mutex_is_locked(&bus->msg_lock))
+			utex_unlock(&bus->msg_lock);
 	}
 
 	return ret;