Quiet spurious pthread_unlock warnings

A message is output in debug builds when pthread_unlock
returns an error. However, in most cases, it should return
EPERM. In fact, if it doesn't return EPERM, it is an
indication of a problem. This commit adjusts accordingly.

Change-Id: Ia5cad89aa6e68e79c1291ea21adffb0fa68f2300

src/rocm_smi.cc

@@ -460,11 +460,19 @@ rsmi_shut_down(void) {
 #if DEBUG
   int ret = 0;
 #endif
-  for (int i = 0; i < smi.monitor_devices().size(); ++i) {
+  for (uint32_t i = 0; i < smi.monitor_devices().size(); ++i) {
 #if DEBUG
     ret = pthread_mutex_unlock(smi.monitor_devices()[i]->mutex());
-    std::cout << "pthread_mutex_unlock() returned " << ret <<
+    if (ret != EPERM) {  // We expect to get EPERM if the lock has already
+                         // been released
+      if (ret == 0) {
+        std::cout << "WARNING: Unlocked monitor_devices lock; " <<
+                    "it should have already been unlocked." << std::endl;
+      } else {
+      std::cout << "WARNING: pthread_mutex_unlock() returned " << ret <<
                    " for device " << i << " in rsmi_shut_down()" << std::endl;
+      }
+    }
 #else
     (void)pthread_mutex_unlock(smi.monitor_devices()[i]->mutex());
 #endif