[23822] Protect PDPStatelessWriter attributes (backport #6100)

[mergify]

Description

This PR attempts to solve the data race produced when a thread clears the attributes of PDPStatelssWriter at mark_all_readers_interested (called in announceParticipantState from events thread, for example), while the values are read from another thread (send_to_fixed_locators called, for example, from the asynchronous send thread → LocatorSelectorSender::send → StatelessWriter::send_nts → PDPStatelessWriter::send_to_fixed_locators).

@Mergifyio backport 3.3.x 3.2.x 2.14.x

Contributor Checklist

• Commit messages follow the project guidelines.

• The code follows the style guidelines of this project.

• Tests that thoroughly check the new feature have been added/Regression tests checking the bug and its fix have been added; the added tests pass locally

• N/A Any new/modified methods have been properly documented using Doxygen.

• N/A Any new configuration API has an equivalent XML API (with the corresponding XSD extension)

• Changes are backport compatible: they do NOT break ABI nor change library core behavior.

• Changes are API compatible.

• N/A New feature has been added to the versions.md file (if applicable).

• N/A New feature has been documented/Current behavior is correctly described in the documentation.

• Applicable backports have been included in the description.

Reviewer Checklist

• The PR has a milestone assigned.
• The title and description correctly express the PR's purpose.
• Check contributor checklist is correct.
• If this is a critical bug fix, backports to the critical-only supported branches have been requested.
• Check CI results: changes do not issue any warning.
• Check CI results: failing tests are unrelated with the changes.

---

This is an automatic backport of pull request #6100 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 6ca678b has failed:

On branch mergify/bp/2.14.x/pr-6100
Your branch is up to date with 'origin/2.14.x'.

You are currently cherry-picking commit 6ca678b4.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   src/cpp/rtps/builtin/discovery/participant/simple/PDPStatelessWriter.hpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   src/cpp/rtps/builtin/discovery/participant/simple/PDPStatelessWriter.cpp
	both modified:   test/blackbox/common/RTPSWithRegistrationWriter.hpp

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[emiliocuestaf]

@mergify rebase, please

[mergify]

rebase , please

✅ Branch has been successfully rebased

[mergify]

🧪 CI Insights

Here's what we observed from your CI run for 0e59726.

❌ Job Failures

Pipeline	Job	Health on 2.14.x	Retries	🔍 CI Insights	📄 Logs
Fast-DDS MacOS CI	mac-ci / fastdds_test ()		0	View	View

[emiliocuestaf]

@mergify rebase

[mergify]

rebase

✅ Branch has been successfully rebased