AP_Airspeed: protect sample timestamp while get data

libraries/AP_Airspeed/AP_Airspeed_DLVR.cpp

@@ -98,18 +98,17 @@ void AP_Airspeed_DLVR::timer()
 // return the current differential_pressure in Pascal
 bool AP_Airspeed_DLVR::get_differential_pressure(float &_pressure)
 {
+    WITH_SEMAPHORE(sem);
+
     if ((AP_HAL::millis() - last_sample_time_ms) > 100) {
         return false;
     }
 
-    {
-        WITH_SEMAPHORE(sem);
     if (press_count > 0) {
         pressure = pressure_sum / press_count;
         press_count = 0;
         pressure_sum = 0;
     }
-    }
 
     _pressure = pressure;
     return true;
@@ -118,12 +117,12 @@ bool AP_Airspeed_DLVR::get_differential_pressure(float &_pressure)
 // return the current temperature in degrees C, if available
 bool AP_Airspeed_DLVR::get_temperature(float &_temperature)
 {
+    WITH_SEMAPHORE(sem);
+
     if ((AP_HAL::millis() - last_sample_time_ms) > 100) {
         return false;
     }
 
-    WITH_SEMAPHORE(sem);
-
     if (temp_count > 0) {
         temperature = temperature_sum / temp_count;
         temp_count = 0;

libraries/AP_Airspeed/AP_Airspeed_MS4525.cpp

@@ -223,12 +223,12 @@ void AP_Airspeed_MS4525::_timer()
 // return the current differential_pressure in Pascal
 bool AP_Airspeed_MS4525::get_differential_pressure(float &pressure)
 {
+    WITH_SEMAPHORE(sem);
+
     if ((AP_HAL::millis() - _last_sample_time_ms) > 100) {
         return false;
     }
 
-    WITH_SEMAPHORE(sem);
-
     if (_press_count > 0) {
         _pressure = _press_sum / _press_count;
         _press_count = 0;
@@ -242,12 +242,12 @@ bool AP_Airspeed_MS4525::get_differential_pressure(float &pressure)
 // return the current temperature in degrees C, if available
 bool AP_Airspeed_MS4525::get_temperature(float &temperature)
 {
+    WITH_SEMAPHORE(sem);
+
     if ((AP_HAL::millis() - _last_sample_time_ms) > 100) {
         return false;
     }
 
-    WITH_SEMAPHORE(sem);
-
     if (_temp_count > 0) {
         _temperature = _temp_sum / _temp_count;
         _temp_count = 0;

libraries/AP_Airspeed/AP_Airspeed_MS5525.cpp

@@ -264,12 +264,12 @@ void AP_Airspeed_MS5525::timer()
 // return the current differential_pressure in Pascal
 bool AP_Airspeed_MS5525::get_differential_pressure(float &_pressure)
 {
+    WITH_SEMAPHORE(sem);
+
     if ((AP_HAL::millis() - last_sample_time_ms) > 100) {
         return false;
     }
 
-    WITH_SEMAPHORE(sem);
-
     if (press_count > 0) {
         pressure = pressure_sum / press_count;
         press_count = 0;
@@ -283,12 +283,12 @@ bool AP_Airspeed_MS5525::get_differential_pressure(float &_pressure)
 // return the current temperature in degrees C, if available
 bool AP_Airspeed_MS5525::get_temperature(float &_temperature)
 {
+    WITH_SEMAPHORE(sem);
+
     if ((AP_HAL::millis() - last_sample_time_ms) > 100) {
         return false;
     }
 
-    WITH_SEMAPHORE(sem);
-
     if (temp_count > 0) {
         temperature = temperature_sum / temp_count;
         temp_count = 0;

libraries/AP_Airspeed/AP_Airspeed_SDP3X.cpp

@@ -278,19 +278,17 @@ float AP_Airspeed_SDP3X::_correct_pressure(float press)
 // return the current differential_pressure in Pascal
 bool AP_Airspeed_SDP3X::get_differential_pressure(float &pressure)
 {
-    uint32_t now = AP_HAL::millis();
+    WITH_SEMAPHORE(sem);
-    if (now - _last_sample_time_ms > 100) {
+
+    if (AP_HAL::millis() - _last_sample_time_ms > 100) {
         return false;
     }
 
-    {
-        WITH_SEMAPHORE(sem);
     if (_press_count > 0) {
         _press = _press_sum / _press_count;
         _press_count = 0;
         _press_sum = 0;
     }
-    }
 
     pressure = _correct_pressure(_press);
     return true;
@@ -299,12 +297,12 @@ bool AP_Airspeed_SDP3X::get_differential_pressure(float &pressure)
 // return the current temperature in degrees C, if available
 bool AP_Airspeed_SDP3X::get_temperature(float &temperature)
 {
+    WITH_SEMAPHORE(sem);
+
     if ((AP_HAL::millis() - _last_sample_time_ms) > 100) {
         return false;
     }
 
-    WITH_SEMAPHORE(sem);
-
     if (_temp_count > 0) {
         _temp = _temp_sum / _temp_count;
         _temp_count = 0;