fix possible race condition

Author: hathach

cores/nRF5/HardwarePWM.cpp

@@ -289,10 +289,13 @@ bool HardwarePWM::takeOwnership(uintptr_t token)
 
   // This function must not be called within ISR
   taskENTER_CRITICAL();
-  _owner_token = token;
+  if ( this->_owner_token == 0 )
+  {
+    _owner_token = token;
+  }
   taskEXIT_CRITICAL();
 
-  return true;
+  return _owner_token == token;
 }
 
 // returns true ONLY when (1) no PWM channel has a pin attached, and (2) the owner token matches
@@ -320,8 +323,11 @@ bool HardwarePWM::releaseOwnership(uintptr_t token)
 
   // This function must not be called within ISR
   taskENTER_CRITICAL();
-  _owner_token = 0;
+  if ( this->_owner_token == token )
+  {
+    _owner_token = 0;
+  }
   taskEXIT_CRITICAL();
 
-  return true;
+  return _owner_token == 0;
 }

libraries/Servo/src/nrf52/Servo.cpp

@@ -48,11 +48,19 @@ uint8_t Servo::attach(int pin, int min, int max)
   }
   bool succeeded = false;
 
-  if (min < MIN_PULSE_WIDTH) min = MIN_PULSE_WIDTH;
-  if (max > MAX_PULSE_WIDTH) max = MAX_PULSE_WIDTH;
+  if (min < MIN_PULSE_WIDTH)
+  {
+    min = MIN_PULSE_WIDTH;
+  }
+
+  if (max > MAX_PULSE_WIDTH)
+  {
+    max = MAX_PULSE_WIDTH;
+  }
 
   //fix min if conversion to pulse cycle value is too low
-  if ( (min/DUTY_CYCLE_RESOLUTION) * DUTY_CYCLE_RESOLUTION < min) {
+  if ( (min / DUTY_CYCLE_RESOLUTION) * DUTY_CYCLE_RESOLUTION < min )
+  {
     min += DUTY_CYCLE_RESOLUTION;
   }