Ungraceful exit error

[krynju]

This showed up on process exit and looks pretty weird
This is on Julia 1.6.5 with 2 threads and this /Downloads/src/Curl/Multi.jl:98 line corresponds to this close here

Downloads.jl/src/Curl/Multi.jl

Line 102 in 78255d4

close(easy.output)

It's very likely Downloads.jl is being used on both threads here, so it might be just a result of thread safety issues, but I haven't seen this error mentioned anywhere, so it may be something new

ERROR: LoadError: val already in a list
Stacktrace:
  [1] error(s::String)
    @ Base ./error.jl:33
  [2] push!
    @ ./linked_list.jl:53 [inlined]
  [3] wait(c::Base.GenericCondition{Base.Threads.SpinLock})
    @ Base ./condition.jl:103
  [4] lock(rl::ReentrantLock)
    @ Base ./lock.jl:100
  [5] lock
    @ ./condition.jl:73 [inlined]
  [6] lock
    @ ./channels.jl:424 [inlined]
  [7] close(c::Channel{Vector{UInt8}}, excp::InvalidStateException) (repeats 2 times)
    @ Base ./channels.jl:183
  [8] check_multi_info(multi::Downloads.Curl.Multi)
    @ Downloads.Curl /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Downloads/src/Curl/Multi.jl:98
  [9] (::Downloads.Curl.var"#39#41"{Int32, Downloads.Curl.Multi})()
    @ Downloads.Curl /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Downloads/src/Curl/Multi.jl:122
 [10] lock(f::Downloads.Curl.var"#39#41"{Int32, Downloads.Curl.Multi}, l::ReentrantLock)
    @ Base ./lock.jl:187
 [11] event_callback(uv_poll_p::Ptr{Nothing}, status::Int32, events::Int32)
    @ Downloads.Curl /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.6/Downloads/src/Curl/Multi.jl:120
 [12] poptask(W::Base.InvasiveLinkedListSynchronized{Task})
    @ Base ./task.jl:760
 [13] wait()
    @ Base ./task.jl:769
 [14] wait(c::Base.GenericCondition{Base.Threads.SpinLock})
    @ Base ./condition.jl:106
 [15] _wait(t::Task)
    @ Base ./task.jl:293
 [16] sync_end(c::Channel{Any})
    @ Base ./task.jl:349
 [17] macro expansion
    @ ./task.jl:388 [inlined]

[ericphanson]

This is an error I've seen a lot with Downloads pre-1.7.3 or 1.8 (both of which include a bunch of thread safety fixes from #157 and others). We backported these to 1.7.3 in #175 but we should also backport them to 1.6. Though while they are bugfixes they are pretty complicated and someone already hinted at an issue on 1.7.3: https://discourse.julialang.org/t/julia-v1-7-3-has-been-released/81683/3. So maybe the 1.6 backport should wait until it's been tested in the wild on 1.7.3 a bit more? not sure

[StefanKarpinski]

Has anyone seen this error on a more recent Julia?