Release the Python GIL when running PythonEventProcessor.

[jpivarski]

The .run() method is blocking, so one might want to put it into a Python threading.Thread. However, the Python interpreter would still block because of the GIL. This correction releases the GIL so that CMSSW can run while Python is running.

Tested on a simple example: observed concurrent execution and no segmentation faults.

[cmsbuild]

A new Pull Request was created by @jpivarski (Jim Pivarski) for master.

It involves the following packages:

FWCore/PythonFramework

@cmsbuild, @smuzaffar, @Dr15Jones, @davidlange6 can you please review it and eventually sign? Thanks.
@Martin-Grunewald, @wddgit this is something you requested to watch as well.
@davidlange6 you are the release manager for this.

cms-bot commands are listed here

[Dr15Jones]

please test

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-any-integration/19740/console Started: 2017/05/10 23:01

[cmsbuild]

+1
Tested at: 988178c
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-18683/19740/summary.html

[cmsbuild]

Comparison job queued.

[Dr15Jones]

+1

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-18683/19740/summary.html

Comparison Summary:

• No significant changes to the logs found
• Reco comparison results: 0 differences found in the comparisons
• DQMHistoTests: Total files compared: 24
• DQMHistoTests: Total histograms compared: 1829453
• DQMHistoTests: Total failures: 32085
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 1797188
• DQMHistoTests: Total skipped: 180
• DQMHistoTests: Total Missing objects: 0
• Checked 98 log files, 14 edm output root files, 24 DQM output files

[cmsbuild]

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

[davidlange6]

+1