Merge pull request OpenMathLib#5350 from martin-frbg/issue5341

Declare the server_lock mutex volatile in addition to static

Author: martin-frbg

driver/others/blas_server.c

@@ -119,11 +119,11 @@ static void * blas_thread_buffer[MAX_CPU_NUMBER];
 
 /* Local Variables */
 #if   defined(USE_PTHREAD_LOCK)
-static pthread_mutex_t  server_lock    = PTHREAD_MUTEX_INITIALIZER;
+volatile static pthread_mutex_t  server_lock    = PTHREAD_MUTEX_INITIALIZER;
 #elif defined(USE_PTHREAD_SPINLOCK)
-static pthread_spinlock_t  server_lock = 0;
+volatile static pthread_spinlock_t  server_lock = 0;
 #else
-static unsigned long server_lock       = 0;
+volatile static unsigned long server_lock       = 0;
 #endif
 
 #define THREAD_STATUS_SLEEP		2