ITS#9181 Fix race on Windows mutex init

include/ldap_int_thread.h

@@ -152,10 +152,13 @@ typedef HANDLE	ldap_int_thread_mutex_t;
 typedef HANDLE	ldap_int_thread_cond_t;
 typedef DWORD	ldap_int_thread_key_t;
 
+LDAP_F( int )
+ldap_pvt_thread_mutex_init_first LDAP_P(( ldap_pvt_thread_mutex_t *mutex ));
+
 #ifndef LDAP_INT_MUTEX_NULL
 #define LDAP_INT_MUTEX_NULL		((HANDLE)0)
 #define LDAP_INT_MUTEX_FIRSTCREATE(m) \
-		((void) ((m) || ldap_pvt_thread_mutex_init(&(m))))
+		ldap_pvt_thread_mutex_init_first(&(m))
 #endif
 
 LDAP_END_DECL

libraries/libldap_r/thr_nt.c

@@ -161,6 +161,17 @@ ldap_pvt_thread_mutex_init( ldap_pvt_thread_mutex_t *mutex )
 	return ( 0 );
 }
 
+int
+ldap_pvt_thread_mutex_init_first( ldap_pvt_thread_mutex_t *mutex )
+{
+	if ( *mutex == NULL ) {
+		HANDLE p = CreateMutex( NULL, 0, NULL );
+		if ( InterlockedCompareExchangePointer((PVOID*)mutex, (PVOID)p, NULL) != NULL)
+			CloseHandle( p );
+	}
+	return ( 0 );
+}
+
 int
 ldap_pvt_thread_mutex_recursive_init( ldap_pvt_thread_mutex_t *mutex )
 {