TDatabasePDG is not thread safe

[c-dilks]

Environment: (where does this bug occur, have you tried other environments)

• Which branch (often main for latest released): main
• Which version (or HEAD for the most recent on git):
• Any specific OS or system where the issue occurs?
• Any special versions of ROOT or Geant4?

Steps to reproduce: (give a step by step account of how to trigger the bug)

See root-project/root#11580

We use this in the following:

src/algorithms/tracking/TruthTrackSeeding.h
src/algorithms/tracking/TruthTrackSeeding.cc
src/algorithms/tracking/TrackParamTruthInit.h
src/algorithms/tracking/TrackParamTruthInit.cc
src/algorithms/pid/IrtCherenkovParticleID.h    (in dev branch `irt-algo`)
src/algorithms/pid/IrtCherenkovParticleID.cc   (in dev branch `irt-algo`)

Thanks to @wdconinc for pointing this out in #416.

Potential Solutions

• Use a mutex
• Contribute a PR to root to fix the issue there for all
• Port Juggler's particle service

[wdconinc]

Port Juggler's particle service

I wouldn't necessarily simply port the service from juggler: it was quick to replicate the particle table, but would have been better to use an external reference for that, in particular if more info will be needed in the future.

I'd probably suggest a service that initializes its table based on TDatabasePDG and then continues to serve it in a thread safe way.

[DraTeots]

Agree with @wdconinc