[DAQ] fix DAQSource race condition (15_0_X)

[smorovic]

PR description:

Buffer offset pointers were getting used by main loop while reader threads could still be using them for file reading, creating a race. This does not affect production HLT, but can affect SuperFragmentBuilder test and Phase2 development kit that will use DAQSource.
It does not affect current production HLT input source, FEDRawDataCollection.

PR validation:

Debugged and fixed on a HLT setup in daq3val.

If this PR is a backport please specify the original PR and why you need to backport that PR. If this PR will be backported please specify to which release cycle the backport is meant for:

Backport of #47767

[cmsbuild]

A new Pull Request was created by @smorovic for CMSSW_15_0_X.

It involves the following packages:

• EventFilter/Utilities (daq)

@cmsbuild, @emeschi, @smorovic can you please review it and eventually sign? Thanks.
@Martin-Grunewald, @missirol this is something you requested to watch as well.
@antoniovilela, @mandrenguyen, @rappoccio, @sextonkennedy you are the release manager for this.

cms-bot commands are listed here

• Backported from [DAQ] fix DAQSource race condition (15_1_X) #47767

[cmsbuild]

cms-bot internal usage

[smorovic]

type bug-fix

[smorovic]

backport of #47767

[smorovic]

@cmsbuild please test

[cmsbuild]

+1

Size: This PR adds an extra 32KB to repository
Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-af8cd7/45351/summary.html
COMMIT: 2f0f57a
CMSSW: CMSSW_15_0_X_2025-04-02-1100/el8_amd64_gcc12
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week1/cms-sw/cmssw/47768/45351/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• No significant changes to the logs found
• Reco comparison results: 14 differences found in the comparisons
• DQMHistoTests: Total files compared: 50
• DQMHistoTests: Total histograms compared: 3999716
• DQMHistoTests: Total failures: 57
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3999639
• DQMHistoTests: Total skipped: 20
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 49 files compared)
• Checked 218 log files, 189 edm output root files, 50 DQM output files
• TriggerResults: no differences found

[smorovic]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_15_0_X IBs (tests are also fine) and once validation in the development release cycle CMSSW_15_1_X is complete. This pull request will now be reviewed by the release team before it's merged. @sextonkennedy, @rappoccio, @antoniovilela, @mandrenguyen (and backports should be raised in the release meeting by the corresponding L2)