Pre-allocated, thread-save buffer arrays

In my program, I have a loop where I need a buffer array. The required size of the buffer changes only a few times during the run. Also, I am using multithreading. So, the buffer should be thread-safe.

The following script is what I came up with. A const array _buffer is declared. Function _get_buffer returns the buffer, resizing the array if needed. Is there any problem with this method?

Also, is there a better way, or a package for pre-allocating and changing buffer sizes?

using Base.Threads

# Preallocated buffer array
const _buffer = [Array{Float64, 2}(undef, 0, 0)]

"""Get preallocated buffer in a thread-safe way.
Resize buffer if the size is different from the needed size"""
function _get_buffer(buffer::Vector{Array{T, N}}, size_needed::NTuple{N, Int}) where {T, N}
    tid = threadid()
    if size(buffer[tid]) != size_needed
        buffer[tid] = zeros(T, size_needed)

# Usage
Nlist = vcat(repeat([40], 10), repeat([60], 10)) # Size of the buffer array for each iteration

@threads for N in Nlist
    arr = _get_buffer(_buffer, (N, N))
    # Do something with arr..
    arr .= 1.0