Fix for multiprocessing in RecoTrack Validation script

[lecriste]

PR description:

This PR fixes a race condition introduced with the multiprocessing package.
No change is expected in the output as this concerns a plotting script.

PR validation:

The errors reported in #35827 are gone.

[cmsbuild]

+code-checks

Logs: https://cmssdt.cern.ch/SDT/code-checks/cms-sw-PR-35884/26281

• This PR adds an extra 52KB to repository

[cmsbuild]

A new Pull Request was created by @lecriste (Leonardo Cristella) for master.

It involves the following packages:

• Validation/RecoTrack (dqm)

@emanueleusai, @ahmad3213, @cmsbuild, @jfernan2, @pmandrik, @pbo0, @rvenditti can you please review it and eventually sign? Thanks.
@felicepantaleo, @GiacomoSguazzoni, @JanFSchulte, @rovere, @VinInn, @ebrondol, @wmtford, @mmusich, @mtosi, @dgulhan this is something you requested to watch as well.
@perrotta, @dpiparo, @qliphy you are the release manager for this.

cms-bot commands are listed here

[mmusich]

please test

[VinInn]

It did not crash and produced plots

[mmusich]

@lecriste would you mind changing the PR title by making it a little more self-explanatory (again for the sake of being able to read the release notes)

[cmsbuild]

-1

Failed Tests: UnitTests RelVals-INPUT
Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-d9b3da/20024/summary.html
COMMIT: 337ef45
CMSSW: CMSSW_12_1_X_2021-10-27-2300/slc7_amd64_gcc900
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmssw/35884/20024/install.sh to create a dev area with all the needed externals and cmssw changes.

Unit Tests

I found errors in the following unit tests:

---> test TestDQMServicesDemo had ERRORS

RelVals-INPUT

• 138.3138.3_RunMinimumBias2021Splash+RunMinimumBias2021Splash+RECODR3Splash+HARVESTDR3/step2_RunMinimumBias2021Splash+RunMinimumBias2021Splash+RECODR3Splash+HARVESTDR3.log

Comparison Summary

Summary:

• No significant changes to the logs found
• Reco comparison results: 2 differences found in the comparisons
• DQMHistoTests: Total files compared: 42
• DQMHistoTests: Total histograms compared: 2901440
• DQMHistoTests: Total failures: 6
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 2901412
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 41 files compared)
• Checked 177 log files, 37 edm output root files, 42 DQM output files
• TriggerResults: no differences found

[mmusich]

failures are unrelated.

[jfernan2]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next master IBs (but tests are reportedly failing). This pull request will now be reviewed by the release team before it's merged. @perrotta, @dpiparo, @qliphy (and backports should be raised in the release meeting by the corresponding L2)

[qliphy]

+1
failure is unrelated and will be fixed by #35905

[qliphy]

merge