Add function reinit_task

[efaulhaber]

JuliaSIMD/Polyester.jl#154 caused Trixi.jl CI to freeze sometimes.
I don't have a MWE for this, but the solution is to only re-initialize failed tasks.

To summarize the previous developments:

• ThreadingUtilities.checktask did not throw an error, which means that threads with errors just failed silently (Threads fail silently on error Polyester.jl#153).
• Throw an error in checktask when a task failed #54 changed this behavior to throw an error.
• Polyester.reset_threads! also used checktask, which now throws errors, so #154 changed this to call ThreadingUtilities.initialize_task instead of checktask. However, this initializes all tasks, not just the failed ones like before all of these PRs. Apparently, this can cause freezing.
• This PR adds reinit_task, which is the same as the old checktask and Reset only failed tasks in reset_threads! Polyester.jl#160 uses this in reset_threads!.

[efaulhaber]

CC @oscardssmith

[ranocha]

Thanks! This looks good to me.

[oscardssmith]

rerunning ci

[efaulhaber]

Looks like everything is passing except nightly macOS.

[oscardssmith]

The segfault is somewhat concerning (as is the use of deprecated LLVM code). We really should replace the hand-rolled LLVM with Julia equivalents since LLVM has absolutely no stability.

[efaulhaber]

I had several segfaults when I ran the tests locally, all from the "ThreadingUtilities" testset. Which deprecated LLVM code are you talking about?

[oscardssmith]

If you look at the CI logs, there's a bunch of

WARNING: llvmcall with integer pointers is deprecated.
Use actual pointers instead, replacing i32 or i64 with i8* or ptr
in _all(Any, Any, Base.Colon) at anyall.jl
WARNING: llvmcall with integer pointers is deprecated.
Use actual pointers instead, replacing i32 or i64 with i8* or ptr
in test_copy(Any, Any) at /Users/runner/work/ThreadingUtilities.jl/ThreadingUtilities.jl/test/threadingutilities.jl

but really the whole https://github.com/JuliaSIMD/ThreadingUtilities.jl/blob/main/src/atomics.jl should be written in Julia rather than LLVM.

[oscardssmith]

I wonder if the problem is

ThreadingUtilities.jl/src/threadtasks.jl

Line 2 in 54bdc4e

p::Ptr{UInt}

(specifically the fact that there doesn't appear to be anything here to ensure alignment)

[efaulhaber]

This stuff is unfortunately way out of the scope of my expertise.

[ranocha]

Since this PR doesn't change the code with deprecated LLVM features, I would prefer merging it, as it represents a strict improvement and is required to fix some issues with Polyester.jl.
The other issues should be handled in another PR.