diff --git a/src/drivers/device/vdev_posix.cpp b/src/drivers/device/vdev_posix.cpp
index 165c60d6ea..b00536f0f6 100644
--- a/src/drivers/device/vdev_posix.cpp
+++ b/src/drivers/device/vdev_posix.cpp
@@ -278,8 +278,12 @@ extern "C" {
 		}
 
 		PX4_DEBUG("Called px4_poll timeout = %d", timeout);
+
 		px4_sem_init(&sem, 0, 0);
 
+		// sem use case is a signal
+		px4_sem_setprotocol(&sem, SEM_PRIO_NONE);
+
 		// Go through all fds and check them for a pollable state
 		bool fd_pollable = false;
 
@@ -409,6 +413,11 @@ extern "C" {
 	void px4_enable_sim_lockstep()
 	{
 		px4_sem_init(&lockstep_sem, 0, 0);
+
+		// lockstep_sem use case is a signal
+
+		px4_sem_setprotocol(&lockstep_sem, SEM_PRIO_NONE);
+
 		sim_lockstep = true;
 		sim_delay = false;
 	}
diff --git a/src/drivers/px4io/px4io_serial.cpp b/src/drivers/px4io/px4io_serial.cpp
index f5a08d8545..ac50d81fc5 100644
--- a/src/drivers/px4io/px4io_serial.cpp
+++ b/src/drivers/px4io/px4io_serial.cpp
@@ -231,6 +231,9 @@ PX4IO_serial::~PX4IO_serial()
 	px4_arch_unconfiggpio(PX4IO_SERIAL_TX_GPIO);
 	px4_arch_unconfiggpio(PX4IO_SERIAL_RX_GPIO);
 
+	/* Disable APB clock for the USART peripheral */
+	modifyreg32(STM32_RCC_APB2ENR, RCC_APB2ENR_USART6EN, 0);
+
 	/* and kill our semaphores */
 	px4_sem_destroy(&_completion_semaphore);
 	px4_sem_destroy(&_bus_semaphore);
@@ -263,6 +266,10 @@ PX4IO_serial::init()
 		return -1;
 	}
 
+
+	/* Enable the APB clock for the USART peripheral */
+	modifyreg32(STM32_RCC_APB2ENR, 0, RCC_APB2ENR_USART6EN);
+
 	/* configure pins for serial use */
 	px4_arch_configgpio(PX4IO_SERIAL_TX_GPIO);
 	px4_arch_configgpio(PX4IO_SERIAL_RX_GPIO);
@@ -294,6 +301,11 @@ PX4IO_serial::init()
 
 	/* create semaphores */
 	px4_sem_init(&_completion_semaphore, 0, 0);
+
+	/* _completion_semaphore use case is a signal */
+
+	px4_sem_setprotocol(&_completion_semaphore, SEM_PRIO_NONE);
+
 	px4_sem_init(&_bus_semaphore, 0, 1);
 
 
@@ -311,7 +323,7 @@ PX4IO_serial::ioctl(unsigned operation, unsigned &arg)
 	case 1:		/* XXX magic number - test operation */
 		switch (arg) {
 		case 0:
-			lowsyslog("test 0\n");
+			syslog(LOG_INFO, "test 0\n");
 
 			/* kill DMA, this is a PIO test */
 			stm32_dmastop(_tx_dma);
@@ -338,7 +350,7 @@ PX4IO_serial::ioctl(unsigned operation, unsigned &arg)
 					}
 
 					if (count >= 5000) {
-						lowsyslog("==== test 1 : %u failures ====\n", fails);
+						syslog(LOG_INFO, "==== test 1 : %u failures ====\n", fails);
 						perf_print_counter(_pc_txns);
 						perf_print_counter(_pc_dmasetup);
 						perf_print_counter(_pc_retries);
@@ -357,7 +369,7 @@ PX4IO_serial::ioctl(unsigned operation, unsigned &arg)
 			}
 
 		case 2:
-			lowsyslog("test 2\n");
+			syslog(LOG_INFO, "test 2\n");
 			return 0;
 		}
 
@@ -597,7 +609,7 @@ PX4IO_serial::_wait_complete()
 		}
 
 		/* we might? see this for EINTR */
-		lowsyslog("unexpected ret %d/%d\n", ret, errno);
+		syslog(LOG_ERR, "unexpected ret %d/%d\n", ret, errno);
 	}
 
 	/* reset DMA status */
diff --git a/src/modules/dataman/dataman.c b/src/modules/dataman/dataman.c
index da8ef8ffb9..9992f4cbfc 100644
--- a/src/modules/dataman/dataman.c
+++ b/src/modules/dataman/dataman.c
@@ -274,6 +274,10 @@ create_work_item(void)
 	/* If we got one then lock the item*/
 	if (item) {
 		px4_sem_init(&item->wait_sem, 1, 0);        /* Caller will wait on this... initially locked */
+
+		/* item->wait_sem use case is a signal */
+
+		px4_sem_setprotocol(&item->wait_sem, SEM_PRIO_NONE);
 	}
 
 	/* return the item pointer, or NULL if all failed */
@@ -922,6 +926,10 @@ task_main(int argc, char *argv[])
 
 	px4_sem_init(&g_work_queued_sema, 1, 0);
 
+	/* g_work_queued_sema use case is a signal */
+
+	px4_sem_setprotocol(&g_work_queued_sema, SEM_PRIO_NONE);
+
 	if (!on_disk) {
 
 		/* In memory */
@@ -1135,6 +1143,10 @@ start(void)
 
 	px4_sem_init(&g_init_sema, 1, 0);
 
+	/* g_init_sema use case is a signal */
+
+	px4_sem_setprotocol(&g_init_sema, SEM_PRIO_NONE);
+
 	/* start the worker thread with low priority for disk IO */
 	if ((task = px4_task_spawn_cmd("dataman", SCHED_DEFAULT, SCHED_PRIORITY_DEFAULT - 10, 1200, task_main, NULL)) <= 0) {
 		warn("task start failed");
diff --git a/src/modules/logger/logger.cpp b/src/modules/logger/logger.cpp
index 0e06cf46ad..efd3e1ac1d 100644
--- a/src/modules/logger/logger.cpp
+++ b/src/modules/logger/logger.cpp
@@ -723,6 +723,12 @@ void Logger::run()
 	memset(&timer_call, 0, sizeof(hrt_call));
 	px4_sem_t timer_semaphore;
 	px4_sem_init(&timer_semaphore, 0, 0);
+
+	/* timer_semaphore use case is a signal */
+
+	px4_sem_setprotocol(&timer_semaphore, SEM_PRIO_NONE);
+
+
 	hrt_call_every(&timer_call, _log_interval, _log_interval, timer_callback, &timer_semaphore);
 
 	// check for new subscription data
diff --git a/src/modules/muorb/adsp/uORBFastRpcChannel.hpp b/src/modules/muorb/adsp/uORBFastRpcChannel.hpp
index 37955603fd..2355040cb0 100644
--- a/src/modules/muorb/adsp/uORBFastRpcChannel.hpp
+++ b/src/modules/muorb/adsp/uORBFastRpcChannel.hpp
@@ -222,6 +222,8 @@ private: // data members
 		Semaphore()
 		{
 			sem_init(&_Sem, 0, 0);
+			/* _Sem use case is a signal */
+			px4_sem_setprotocol(&_Sem, SEM_PRIO_NONE);
 		}
 		~Semaphore()
 		{
diff --git a/src/modules/syslink/syslink_main.cpp b/src/modules/syslink/syslink_main.cpp
index d0a41fc504..a161b7aea8 100644
--- a/src/modules/syslink/syslink_main.cpp
+++ b/src/modules/syslink/syslink_main.cpp
@@ -107,6 +107,8 @@ Syslink::Syslink() :
 	_bstate(BAT_DISCHARGING)
 {
 	px4_sem_init(&memory_sem, 0, 0);
+	/* memory_sem use case is a signal */
+	px4_sem_setprotocol(&memory_sem, SEM_PRIO_NONE);
 }
 
 
diff --git a/src/modules/uavcan/uavcan_main.cpp b/src/modules/uavcan/uavcan_main.cpp
index ba16a2aff1..7816a3125f 100644
--- a/src/modules/uavcan/uavcan_main.cpp
+++ b/src/modules/uavcan/uavcan_main.cpp
@@ -110,6 +110,8 @@ UavcanNode::UavcanNode(uavcan::ICanDriver &can_driver, uavcan::ISystemClock &sys
 	if (res < 0) {
 		std::abort();
 	}
+	/* _server_command_sem use case is a signal */
+	px4_sem_setprotocol(&_server_command_sem, SEM_PRIO_NONE);
 
 	if (_perfcnt_node_spin_elapsed == nullptr) {
 		errx(1, "uavcan: couldn't allocate _perfcnt_node_spin_elapsed");
diff --git a/src/modules/uavcan/uavcan_virtual_can_driver.hpp b/src/modules/uavcan/uavcan_virtual_can_driver.hpp
index d395f2b76c..bdd7a4ded8 100644
--- a/src/modules/uavcan/uavcan_virtual_can_driver.hpp
+++ b/src/modules/uavcan/uavcan_virtual_can_driver.hpp
@@ -345,19 +345,23 @@ class VirtualCanDriver : public uavcan::ICanDriver,
 {
 	class Event
 	{
-		FAR sem_t sem;
+		FAR px4_sem_t sem;
 
 
 	public:
 
 		int init()
 		{
-			return sem_init(&sem, 0, 0);
+			int rv = px4_sem_init(&sem, 0, 0);
+			if (rv == 0) {
+				px4_sem_setprotocol(&sem, SEM_PRIO_NONE);
+			}
+			return rv;
 		}
 
 		int deinit()
 		{
-			return sem_destroy(&sem);
+			return px4_sem_destroy(&sem);
 		}
 
 
@@ -388,7 +392,7 @@ class VirtualCanDriver : public uavcan::ICanDriver,
 						abstime.tv_nsec -= NsPerSec;
 					}
 
-					(void)sem_timedwait(&sem, &abstime);
+					(void)px4_sem_timedwait(&sem, &abstime);
 				}
 			}
 		}
@@ -396,7 +400,7 @@ class VirtualCanDriver : public uavcan::ICanDriver,
 		void signal()
 		{
 			int count;
-			int rv = sem_getvalue(&sem, &count);
+			int rv = px4_sem_getvalue(&sem, &count);
 
 			if (rv > 0 && count <= 0) {
 				px4_sem_post(&sem);
diff --git a/src/platforms/posix/px4_layer/px4_sem.cpp b/src/platforms/posix/px4_layer/px4_sem.cpp
index 67e59bc8fd..e09e6ccc7a 100644
--- a/src/platforms/posix/px4_layer/px4_sem.cpp
+++ b/src/platforms/posix/px4_layer/px4_sem.cpp
@@ -60,6 +60,11 @@ int px4_sem_init(px4_sem_t *s, int pshared, unsigned value)
 	return 0;
 }
 
+int px4_sem_setprotocol(px4_sem_t *s, int protocol)
+{
+	return 0;
+}
+
 int px4_sem_wait(px4_sem_t *s)
 {
 	int ret = pthread_mutex_lock(&(s->lock));
diff --git a/src/platforms/px4_sem.h b/src/platforms/px4_sem.h
index 00b4f5db4e..c880e88c89 100644
--- a/src/platforms/px4_sem.h
+++ b/src/platforms/px4_sem.h
@@ -41,6 +41,14 @@
 
 #include <semaphore.h>
 
+#if !defined(__PX4_NUTTX)
+/* Values for protocol attribute */
+
+#define SEM_PRIO_NONE             0
+#define SEM_PRIO_INHERIT          1
+#define SEM_PRIO_PROTECT          2
+#define sem_setprotocol(s,p)
+#endif
 
 #ifdef __PX4_DARWIN
 
@@ -53,6 +61,7 @@ typedef struct {
 } px4_sem_t;
 
 __EXPORT int		px4_sem_init(px4_sem_t *s, int pshared, unsigned value);
+__EXPORT int		px4_sem_setprotocol(px4_sem_t *s, int protocol);
 __EXPORT int		px4_sem_wait(px4_sem_t *s);
 __EXPORT int		px4_sem_timedwait(px4_sem_t *sem, const struct timespec *abstime);
 __EXPORT int		px4_sem_post(px4_sem_t *s);
@@ -67,11 +76,12 @@ __BEGIN_DECLS
 
 typedef sem_t px4_sem_t;
 
-#define px4_sem_init	 sem_init
-#define px4_sem_wait	 sem_wait
-#define px4_sem_post	 sem_post
-#define px4_sem_getvalue sem_getvalue
-#define px4_sem_destroy	 sem_destroy
+#define px4_sem_init		sem_init
+#define px4_sem_setprotocol sem_setprotocol
+#define px4_sem_wait		sem_wait
+#define px4_sem_post		sem_post
+#define px4_sem_getvalue	sem_getvalue
+#define px4_sem_destroy		sem_destroy
 
 #ifdef __PX4_QURT
 __EXPORT int		px4_sem_timedwait(px4_sem_t *sem, const struct timespec *abstime);
diff --git a/src/systemcmds/tests/test_dataman.c b/src/systemcmds/tests/test_dataman.c
index c7ae811f1e..0d7a95dac9 100644
--- a/src/systemcmds/tests/test_dataman.c
+++ b/src/systemcmds/tests/test_dataman.c
@@ -171,6 +171,8 @@ int test_dataman(int argc, char *argv[])
 		av[0] = a;
 		av[1] = 0;
 		px4_sem_init(sems + i, 1, 0);
+		/* sems use case is a signal */
+		px4_sem_setprotocol(&sems, SEM_PRIO_NONE);
 
 		/* start the task */
 		if ((task = px4_task_spawn_cmd("dataman", SCHED_DEFAULT, SCHED_PRIORITY_MAX - 5, 2048, task_main, (void *)av)) <= 0) {