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;