Make O2DatabasePDG::Instance() thread-safe and remove duplicate PDG warnings

Author: jackal1-66

DataFormats/simulation/include/SimulationDataFormat/O2DatabasePDG.h

@@ -34,12 +34,13 @@ class O2DatabasePDG
  public:
   static TDatabasePDG* Instance()
   {
-    static bool initialized = false; // initialize this --> adds particles to TDatabasePDG;
-    auto db = TDatabasePDG::Instance();
-    if (!initialized) {
+    // adds the ALICE particles to TDatabasePDG on first use.
+    // Initialisation is done through a local static database to make the Instance() function thread-safe
+    static TDatabasePDG* db = [] {
+      auto db = TDatabasePDG::Instance();
       addALICEParticles(db);
-      initialized = true;
-    }
+      return db;
+    }();
     return db;
   }
 

Detectors/gconfig/data/extra_ions_pdg_table.dat

@@ -706,7 +706,6 @@
  1352 W174                  1000741740 1 100 Ion  222 1.61992e+02 0.00000e+00 0 0 0 -1 0 0
  1353 Hg198                 1000801980 1 100 Ion  240 1.84365e+02 0.00000e+00 0 0 0 -1 0 0
  1354 Pd115                 1000461150 1 100 Ion  138 1.07018e+02 0.00000e+00 0 0 0 -1 0 0
- 1355 Li4                   1000030040 1 100 Ion  9 3.74977e+00 0.00000e+00 0 0 0 -1 0 0
  1356 Lu170                 1000711700 1 100 Ion  213 1.58261e+02 0.00000e+00 0 0 0 -1 0 0
  1357 Ho163                 1000671630 1 100 Ion  201 1.51733e+02 0.00000e+00 0 0 0 -1 0 0
  1358 Tm153                 1000691530 1 100 Ion  207 1.42430e+02 0.00000e+00 0 0 0 -1 0 0

Generators/src/GeneratorFactory.cxx

@@ -140,7 +140,7 @@ void GeneratorFactory::setPrimaryGenerator(o2::conf::SimConfig const& conf, Fair
 
   /** generators **/
 
-  o2::O2DatabasePDG::addALICEParticles(TDatabasePDG::Instance());
+  o2::O2DatabasePDG::Instance(); //--> ALICE particles are added once in this call
   auto genconfig = conf.getGenerator();
 #if defined(GENERATORS_WITH_PYTHIA8) && defined(GENERATORS_WITH_HEPMC3)
   std::string hyperloopExtHybridConfigFile; // set when IS_HYPERLOOP is defined

macro/o2sim.C

@@ -177,8 +177,8 @@ FairRunSim* o2sim_init(bool asservice, bool evalmat = false)
   // run init
   run->Init();
 
-  // add ALICE particles to TDatabasePDG singleton
-  o2::O2DatabasePDG::addALICEParticles(TDatabasePDG::Instance());
+  // ensure ALICE particles are in the TDatabasePDG singleton (added once, thread-safely)
+  o2::O2DatabasePDG::Instance();
 
   long runStart = timestamp;
   {