Add Userspace RCU recipe.

[szmyd]

Specify library name and version: userspace-rcu/0.11.4

Userspace RCU implements a library around the Linux Kernel RCU interface. It is used by benchmarking and metrics gathering libraries at eBay Inc. and a dependency for many of our Open Source projects.

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[prince-chrismc]

👋 thanks for opening this PR and contributing this recipe

I had two small nits and two questsions, I am not familiar with this project so hopefully you can fill in the gaps

[prince-chrismc]

Is there as reason that only on lib at a time is linked again but all of them are copied?

[szmyd]

I'm not sure I follow; this is the package() function so while all library variants are built, only the one selected with the model option is copied into the package (and thus added to the cpp_info linker flags). Am I missing something?

[prince-chrismc]

We try to respect the original projects layout as closely as possible this way existing users of the project can continue what they are doing and new consumers can just follow the upstream docs without Conan getting in the way.

Looking of the project what we'd ideally have is the the projects install and model the pkg_config targets https://github.com/urcu/userspace-rcu/blob/7c40d7f5b2139ec9151daf8410b6b934234220d5/configure.ac#L310-L316

This was, as the original author intended, consumers can pick which libs they link against

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My suggestion is

• deleting the model option
• call the upstream install method (noted Add Userspace RCU recipe. #11595 (comment))
• add components (should be a one to one with the libs) how to docs

[szmyd]

Ah, I see. Thanks for the clarification!

[jgsogo]

I added some suggestions, but they are just suggestions.

[prince-chrismc]

Please do not force push 🙏 GitHub forces us to restart the review which is not fun!

[conan-center-bot]

All green in build 24 (6b29a540f09469da289c5f79f3676327c686629b):

• userspace-rcu/0.11.4@:
  All packages built successfully! (All logs)

  🔸 Informative: This recipe is not ready for Conan v2

  _{We have started the migration process to Conan v2 and exporting recipes successfully will be required in the future.
  This is just an informative note to gain awareness about the process, no need to take any action. The plan is to enforce smaller steps that are easier to fix and, eventually, this conan export step will work.
  See the recipe migration guide to know more about the changes required.}

  ERROR: Error loading conanfile at '/home/conan/w/prod_cci_PR-11595/recipes/userspace-rcu/all/conanfile.py': Unable to load conanfile in /home/conan/w/prod_cci_PR-11595/recipes/userspace-rcu/all/conanfile.py
    File "<frozen importlib._bootstrap_external>", line 728, in exec_module
    File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
    File "/home/conan/w/prod_cci_PR-11595/recipes/userspace-rcu/all/conanfile.py", line 3, in <module>
      from conans import ConanFile, AutoToolsBuildEnvironment, tools
  ImportError: cannot import name 'ConanFile' from 'conans' (/opt/pyenv/versions/3.7.13/lib/python3.7/site-packages/conans/__init__.py)
  

[prince-chrismc]

Looks really good!

[SSE4]

would be nice to reduce it, calling one function (e.g. rcu_register_thread) is enough to test we can compile and link against the library