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@xxxxxxxxxx>
---
?? 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;
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