bt_gatt_notify() blocks thread nrf Connect SDK v2.4

Question

Hi, 
 We're using nrf Connect SDK v2.4 and have issues when calling bt_gatt_notify() from our main thread. The bt_gatt_notify() function blocks even though we have the CONFIG_BT_L2CAP_TX_BUF_COUNT parameter set to 20. What is the earliest version of the SDK which will not block when calling bt_gatt_notify() if one exists? Is there a function we can call to determine how many notifications are pending in the transmit queue?

helpfulchicken · Answer

I ended up "solving" this issue by tracking in the application level whether notification requests had resolved or not. bt_gatt_notify_cb lets me use a callback to catch when it sends successfully, and a disconnect event handler lets me catch when the queue gets cleared as a result of disconnection - either means that one or more items are no longer in the tx queue which means it is safe to do one more notify attempt.