Fix task switch in GC finalizer

[Octogonapus]

I encountered this error:

error in running finalizer: ErrorException("task switch not allowed from inside gc finalizer")
ijl_error at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/rtutils.c:41
ijl_switch at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/task.c:636
try_yieldto at ./task.jl:921
wait at ./task.jl:995
#wait#645 at ./condition.jl:130
wait at ./condition.jl:125 [inlined]
close at ./asyncevent.jl:180
#4 at /home/runner/.julia/packages/ForeignCallbacks/fneAK/src/ForeignCallbacks.jl:117
unknown function (ip: 0x7f2a34baa335)
_jl_invoke at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/gf.c:2894 [inlined]
ijl_apply_generic at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/gf.c:3076
run_finalizer at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/gc.c:318
jl_gc_run_finalizers_in_list at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/gc.c:408
run_finalizers at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/gc.c:454
jl_mutex_unlock at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/julia_locks.h:80 [inlined]
jl_generate_fptr_impl at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/jitlayers.cpp:525
jl_compile_method_internal at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/gf.c:2480 [inlined]
jl_compile_method_internal at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/gf.c:2368
_jl_invoke at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/gf.c:2886 [inlined]
ijl_apply_generic at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/gf.c:3076
_fire_post_update_callback at /home/runner/.julia/packages/AWSCRT/P0HMS/src/ShadowFramework.jl:352
_do_local_shadow_update! at /home/runner/.julia/packages/AWSCRT/P0HMS/src/ShadowFramework.jl:337
unknown function (ip: 0x7f2a34ba22d9)
_jl_invoke at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/gf.c:2894 [inlined]
ijl_apply_generic at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/gf.c:3076
_update_local_shadow_from_delta! at /home/runner/.julia/packages/AWSCRT/P0HMS/src/ShadowFramework.jl:309
shadow_callback at /home/runner/.julia/packages/AWSCRT/P0HMS/src/ShadowFramework.jl:256
#71 at /home/runner/.julia/packages/AWSCRT/P0HMS/src/IOTShadow.jl:74 [inlined]
#51 at /home/runner/.julia/packages/AWSCRT/P0HMS/src/AWSMQTT.jl:595
#3 at /home/runner/.julia/packages/ForeignCallbacks/fneAK/src/ForeignCallbacks.jl:110
unknown function (ip: 0x7f2a34b9d8d2)
_jl_invoke at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/gf.c:2894 [inlined]
ijl_apply_generic at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/gf.c:3076
jl_apply at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/julia.h:1982 [inlined]
start_task at /cache/build/builder-amdci4-6/julialang/julia-release-1-dot-10/src/task.c:1238

It looks like this task switch is caused by the close call in the finalizer here.
This makes sense to me; close is IO after all.

My solution is to wrap close in a new task to defer any potential task switch.

[vchuravy]

Thanks for the PR. I am not currently planning on maintaining this package since it is no longer useful (since Julia 1.9), but I will happily take your PR and release a version.

[Octogonapus]

since it is no longer useful (since Julia 1.9)

Really? How else could I implement something like this: https://github.com/Octogonapus/AWSCRT.jl/blob/main/src/AWSMQTT.jl#L185-L190

Thanks for taking this PR though

[vchuravy]

On Julia 1.9+ (JuliaLang/julia#46609) you can execute full Julia functions on foreign threads. So you could use a Channel or any other concurrent-safe datastructure.

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