Implement a RecursiveMutex class which is an explicit Recursive Mutex. Change the db mutex to a recursive Mutex

src/zm_db.cpp

@@ -24,7 +24,7 @@
 #include "zm_db.h"
 
 MYSQL dbconn;
-Mutex db_mutex;
+RecursiveMutex db_mutex;
 
 bool zmDbConnected = false;
 
@@ -91,15 +91,15 @@ void zmDbClose() {
 }
 
 MYSQL_RES * zmDbFetch(const char * query) {
-  if ( ! zmDbConnected ) {
+  if ( !zmDbConnected ) {
     Error("Not connected.");
     return NULL;
   }
   db_mutex.lock();
 
   if ( mysql_query(&dbconn, query) ) {
-    Error("Can't run query: %s", mysql_error(&dbconn));
     db_mutex.unlock();
+    Error("Can't run query: %s", mysql_error(&dbconn));
     return NULL;
   }
   Debug(4, "Success running query: %s", query);

src/zm_db.h

@@ -41,7 +41,7 @@ class zmDbRow {
 };
 
 extern MYSQL dbconn;
-extern Mutex db_mutex;
+extern RecursiveMutex db_mutex;
 
 bool zmDbConnect();
 void zmDbClose();

src/zm_thread.cpp

@@ -95,6 +95,15 @@ bool Mutex::locked() {
   return( state == EBUSY );
 }
 
+RecursiveMutex::RecursiveMutex() {
+  pthread_mutexattr_t attr;
+  pthread_mutexattr_init(&attr);
+  pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
+
+  if ( pthread_mutex_init(&mMutex, &attr) < 0 )
+    Error("Unable to create pthread mutex: %s", strerror(errno));
+}
+
 Condition::Condition( Mutex &mutex ) : mMutex( mutex ) {
   if ( pthread_cond_init( &mCondition, NULL ) < 0 )
     throw ThreadException( stringtf( "Unable to create pthread condition: %s", strerror(errno) ) );

src/zm_thread.h

@@ -59,27 +59,34 @@ public:
 };
 
 class Mutex {
-friend class Condition;
+  friend class Condition;
 
-private:
-  pthread_mutex_t mMutex;
+  private:
+    pthread_mutex_t mMutex;
 
-public:
-  Mutex();
-  ~Mutex();
+  public:
+    Mutex();
+    ~Mutex();
 
-private:
-  pthread_mutex_t *getMutex() {
-    return( &mMutex );
-  }
+  private:
+    pthread_mutex_t *getMutex() {
+      return &mMutex;
+    }
 
-public:
-  int trylock();
-  void lock();
-  void lock( int secs );
-  void lock( double secs );
-  void unlock();
-  bool locked();
+  public:
+    int trylock();
+    void lock();
+    void lock( int secs );
+    void lock( double secs );
+    void unlock();
+    bool locked();
+};
+
+class RecursiveMutex : public Mutex {
+  private:
+    pthread_mutex_t mMutex;
+  public:
+    RecursiveMutex();
 };
 
 class ScopedMutex {