parameters: new parameter server backend

- parameter backend is now running in a wq and accessible over pub/sub
 - parameters library can call into backend directly (with locking), but operations will gradually start moving to pub/sub
 - majority of parameters migrated as is, only small changes to parameter autosave and parameter notification that are now performed from the WQ thread

platforms/common/include/px4_platform_common/param.h

@@ -118,7 +118,6 @@ public:
 
 	Param()
 	{
-		param_set_used(handle());
 		update();
 	}
 
@@ -164,7 +163,6 @@ public:
 	Param(float &external_val)
 		: _val(external_val)
 	{
-		param_set_used(handle());
 		update();
 	}
 
@@ -208,7 +206,6 @@ public:
 
 	Param()
 	{
-		param_set_used(handle());
 		update();
 	}
 
@@ -254,7 +251,6 @@ public:
 	Param(int32_t &external_val)
 		: _val(external_val)
 	{
-		param_set_used(handle());
 		update();
 	}
 
@@ -298,7 +294,6 @@ public:
 
 	Param()
 	{
-		param_set_used(handle());
 		update();
 	}
 

platforms/common/include/px4_platform_common/px4_work_queue/WorkQueueManager.hpp

@@ -1,6 +1,6 @@
 /****************************************************************************
  *
- *   Copyright (c) 2019-2021 PX4 Development Team. All rights reserved.
+ *   Copyright (c) 2019-2022 PX4 Development Team. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -76,6 +76,8 @@ static constexpr wq_config_t hp_default{"wq:hp_default", 1900, -18};
 
 static constexpr wq_config_t uavcan{"wq:uavcan", 3624, -19};
 
+static constexpr wq_config_t parameter_server{"wq:parameter_server", 4096, -20};
+
 static constexpr wq_config_t ttyS0{"wq:ttyS0", 1632, -21};
 static constexpr wq_config_t ttyS1{"wq:ttyS1", 1632, -22};
 static constexpr wq_config_t ttyS2{"wq:ttyS2", 1632, -23};

platforms/common/uORB/SubscriptionBlocking.hpp

@@ -85,6 +85,7 @@ public:
 
 	virtual ~SubscriptionBlocking()
 	{
+		unregisterCallback();
 		pthread_mutex_destroy(&_mutex);
 		pthread_cond_destroy(&_cv);
 	}

platforms/common/uORB/uORBDeviceNode.cpp

@@ -514,7 +514,7 @@ uORB::DeviceNode::register_callback(uORB::SubscriptionCallback *callback_sub)
 		ATOMIC_ENTER;
 
 		// prevent duplicate registrations
-		for (auto existing_callbacks : _callbacks) {
+		for (const auto &existing_callbacks : _callbacks) {
 			if (callback_sub == existing_callbacks) {
 				ATOMIC_LEAVE;
 				return true;