Fix potential deadlock in setBinLabel.

This one only triggers in the error path, because getFullname tries to
take a lock that we already hold.

However, there is another opportunity for a deadlock via edm::Log*
(which probably takes a lock), and the per ME-locks which could be taken
before or after edm::Log* is called. I reviewed all usages of edm::Log*
in DQMServices/Core and did not see anything problematic.

Note that this is the only usage of edm::Log* in MonitorElement, and it
now avoids taking multiple locks at the same time, so there should not
be any more problems of this type.

DQMServices/Core/src/MonitorElement.cc

@@ -721,18 +721,24 @@ namespace dqm::impl {
 
   /// set bin label for x, y or z axis (axis=1, 2, 3 respectively)
   void MonitorElement::setBinLabel(int bin, const std::string &label, int axis /* = 1 */) {
-    auto access = this->accessMut();
-    update();
-    if (getAxis(access, __PRETTY_FUNCTION__, axis)->GetNbins() >= bin) {
-      getAxis(access, __PRETTY_FUNCTION__, axis)->SetBinLabel(bin, label.c_str());
-    } else {
-#if WITHOUT_CMS_FRAMEWORK
-      std::cout
-#else
-      edm::LogWarning("MonitorElement")
-#endif
-          << "*** MonitorElement: WARNING:"
-          << "setBinLabel: attempting to set label of non-existent bin number for ME: " << getFullname() << " \n";
+    bool fail = false;
+    {
+      auto access = this->accessMut();
+      update();
+      if (getAxis(access, __PRETTY_FUNCTION__, axis)->GetNbins() >= bin) {
+        getAxis(access, __PRETTY_FUNCTION__, axis)->SetBinLabel(bin, label.c_str());
+      } else {
+        fail = true;
+      }
+    }
+    // do this with the ME lock released to prevent a deadlock
+    if (fail) {
+      // this also takes the lock, make sure to release it before going to edm
+      // (which might take more locks)
+      auto name = getFullname();
+      edm::LogWarning("MonitorElement") << "*** MonitorElement: WARNING:"
+                                        << "setBinLabel: attempting to set label of non-existent bin number for ME: "
+                                        << name << " \n";
     }
   }