On Thu, May 23, 2019 at 09:43:14AM +0100, Srinivas Kandagatla wrote:

On 22/05/2019 17:41, Pierre-Louis Bossart wrote:

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On 5/22/19 11:25 AM, Srinivas Kandagatla wrote:

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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

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?????????? } ?????????? return ret;

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On Thu, May 23, 2019 at 10:30:20AM +0100, Srinivas Kandagatla wrote:

On 23/05/2019 10:20, Sanyog Kale wrote:

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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<-----------------------------

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--srini

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?????????? } ?????????? return ret;

--