Make the Julia GC threadsafe when used from GAP.jl #4071
Merged
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When running from multi-threaded Julia, we have to consider the case
that GAP can be called from more than one thread. In those cases, the
variable JuliaTLS may be incorrect. We therefore update it in NewBag(),
where it is depended upon for allocations. It had already been set when
a GC was called from a separate thread.
In order to avoid unnecessary overhead in the single-threaded case, we
do not change JuliaTLS for allocations when there is only one thread, as
determining the current thread-local state pointer can be somewhat
costly (which is why we cache it in JuliaTLS in the first place).