Watchdog: use get_instance to access watchdog hw

drivers/VirtualWatchdog.cpp

@@ -17,11 +17,11 @@
 #ifdef DEVICE_VIRTUAL_WATCHDOG
 
 #include "VirtualWatchdog.h"
+#include "Watchdog.h"
 
 namespace mbed {
 
 VirtualWatchdog *VirtualWatchdog::_first = NULL;
-Watchdog VirtualWatchdog::*_watchdog = NULL;
 
 VirtualWatchdog::VirtualWatchdog(uint32_t timeout, const char *const str): _name(str)
 {
@@ -29,23 +29,16 @@ VirtualWatchdog::VirtualWatchdog(uint32_t timeout, const char *const str): _name
     _is_initialized = false;
     _next = NULL;
     _max_timeout = timeout;
-    // initialize watchdog, just once (driver Watchdog takes care of only one instance there)
-    if (_watchdog == NULL) {
-        _watchdog = new Watchdog();
-        _watchdog.start();
-    }
+    // start watchdog
+     Watchdog& watchdog = Watchdog::get_instance();
+     watchdog.start();
 }
 
 VirtualWatchdog::~VirtualWatchdog()
 {
     if (_is_initialized) {
         stop();
-        // if we are the last VirtualWatchdog in the system, make sure to turn off hw watchdog
-        if (_first == NULL) {
-            _watchdog.stop();
-            delete _watchdog;
-            _watchdog = NULL;
-        }
+        // we do not need to stop hw watchdog, it's ticking by itself
     }
 }
 

drivers/VirtualWatchdog.h

@@ -26,8 +26,6 @@
 #include "platform/mbed_power_mgmt.h"
 #include "mbed_assert.h"
 
-class Watchdog;
-
 namespace mbed {
 
 /** \addtogroup drivers */
@@ -116,7 +114,6 @@ private:
     bool _is_initialized; //To control start and stop functionality
     static VirtualWatchdog *_first; //List to store the user/threads who called start
     VirtualWatchdog *_next;
-    static Watchdog *_watchdog;
 };
 
 } // namespace mbed

drivers/Watchdog.cpp

@@ -36,30 +36,6 @@ namespace mbed {
 bool Watchdog::_running = false;
 static const uint32_t elapsed_ms = MBED_CONF_TARGET_WATCHDOG_TIMEOUT / 2;
 
-Watchdog::Watchdog()
-{
-    core_util_critical_section_enter();
-    if (_running) {
-        // error function does not return thus exit critical section and print an error
-        core_util_critical_section_exit();
-        MBED_ERROR(MBED_MAKE_ERROR(MBED_MODULE_DRIVER, MBED_ERROR_CODE_OUT_OF_RESOURCES), "There's already watchdog in the system");
-    }
-    core_util_critical_section_exit();
-}
-
-Watchdog::~Watchdog()
-{
-    core_util_critical_section_enter();
-    if (_running) {
-        if (stop()) {
-            // some targets might not support stop, thus keep running true in that case
-            _running = false;
-        }
-    }
-    core_util_critical_section_exit();
-}
-
-
 bool Watchdog::start()
 {
     watchdog_status_t sts;
@@ -121,12 +97,12 @@ bool Watchdog::is_running() const
     return _running;
 }
 
-uint32_t Watchdog::get_timeout()
+uint32_t Watchdog::get_timeout() const
 {
     return hal_watchdog_get_reload_value();
 }
 
-uint32_t Watchdog::get_max_timeout()
+uint32_t Watchdog::get_max_timeout() const
 {
     const watchdog_features_t features = hal_watchdog_get_platform_features();
     return features.max_timeout;

drivers/Watchdog.h

@@ -33,12 +33,12 @@ namespace mbed {
 
 /** \addtogroup drivers */
 /** Hardware system timer that will reset the system in the case of system failures or
- *  malfunctions.
+ *  malfunctions. There is only one instance in the system.
  *
  * Example:
  * @code
  *
- * Watchdog watchdog();
+ * Watchdog& watchdog = Watchdog::get_instance();
  * watchdog.start();
  *
  * while (true) {
@@ -50,12 +50,17 @@ namespace mbed {
 class Watchdog : private NonCopyable<Watchdog>  {
 public:
 
-    /** Constructor configured with timeout
-     *
-     */
-    Watchdog();
-    ~Watchdog();
-public:
+    /** As Watchdog might not stop ever, there is just one instance - we use single instance.
+      * This ensures we keep Watchdog alive. To operate watchdog, use start/stop methods.
+    */ 
+    static Watchdog &get_instance()
+    {
+        // Use this implementation of singleton (Meyer's) rather than the one that allocates
+        // the instance on the heap because it ensures destruction at program end (preventing warnings
+        // from memory checking tools, such as valgrind).
+        static Watchdog instance;
+        return instance;
+    }
 
     /** Start the watchdog timer
      *
@@ -100,6 +105,9 @@ public:
     bool is_running() const;
 
 private:
+    Watchdog();
+    ~Watchdog();
+
     static void kick();
     static uint32_t _elapsed_ms;
     static bool _running;