Made statics in NuclearInteractionFTFSimulator thread safe

[Dr15Jones]

The static analyzer identified a thread-safety issue with the static class members of NuclearInteractionFTFSimulator. Using an std::call_once makes sure the array is safely initialized.

NOTE: Someone should check that the Geant 4 classes used in this code can safely be called on different threads.

[cmsbuild]

A new Pull Request was created by @Dr15Jones (Chris Jones) for CMSSW_7_5_X.

Made statics in NuclearInteractionFTFSimulator thread safe

It involves the following packages:

FastSimulation/MaterialEffects

@ssekmen, @nclopezo, @lveldere, @civanch, @mdhildreth, @cmsbuild can you please review it and eventually sign? Thanks.
@Martin-Grunewald, @matt-komm this is something you requested to watch as well.
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[Dr15Jones]

please test

[cmsbuild]

The tests are being triggered in jenkins.

[civanch]

@Dr15Jones , thank you for the fix. FastSim is not yet MT capable, so this this fix will be useful for future.

Concerning Geant4 : all public versions are not yet c++11, however, code is safe, because initialisation of shared data is done in the master thread; if it is not guaranteed that initialisation is done by the master then a mutex lock is set locally in the initialisation method.

I would also agree, that in the case of FastSim we need double check that the code used for FastSim is safe itself and not only in Geant4 context.

[civanch]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_5_X IBs unless changes or unless it breaks tests. This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @nclopezo, @smuzaffar

[cmsbuild]

+1
Tested at: caf9430
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-9064/16/summary.html

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_5_X IBs unless changes (tests are also fine). This pull request requires discussion in the ORP meeting before it's merged. @davidlange6, @nclopezo, @smuzaffar

[davidlange6]

+1