precompile: respect and report cache pidlocking

[IanButterworth]

Follow-up to JuliaLang/julia#49052

Depends on

• Tweak cache pidlocking julia#50214
• add Base.isprecompiled(pkg::PkgId) julia#50218
• Tweak cache pidlocking pt. 2 julia#50254

[KristofferC]

Is it really the package version that is locked on? It's the filename no (which doesn't include the version) but has a mix of other things like the project, sysimage, etc.

[IanButterworth]

Specifically it's the sourcepath.

[KristofferC]

Okay so that means that two julias with e.g. different sysimage that are precompiling will wait on each other even if they would produce a different precompile file in the end and there wouldn't really be a need for a lock, or?

With preferences, I don't think you even know what the end resulting file name will be until the process is done :/

[IanButterworth]

Right. I don't think we can be specific to the cachefile because of all that

[IanButterworth]

xref JuliaLang/julia#50206

[vchuravy]

I will also raise my earlier point again. We need to make this robust against user-interuption. Or at least make it obvious to the user how to cleanup after interruptions.

pacman as an example tells me which file it tried to acquire and if I think the other process was interrupted that I should remove it

[IanButterworth]

Do you mean in addition to the stale detection stuff that mkpidlock does automatically?

[IanButterworth]

Turns out that was disabled by accident. Fixed in JuliaLang/julia#50214

[IanButterworth]

This has addressed feedback and has tests, and I want to work on Pkg.precompile stuff after this so I'm going to merge and bump the stdlib, and then add the news to base NEWS