gh-151223: fix tsan data races in load global specializations #3188

Job	Run time
aarch64-apple-darwin/clang	10m 24s
x86_64-unknown-linux-gnu/gcc	10m 7s
x86_64-apple-darwin/clang	19m 18s
aarch64-unknown-linux-gnu/gcc	7m 36s
x86_64-unknown-linux-gnu/gcc-free-threading	1h 0m 15s
	1h 47m 40s

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