gh-151223: fix tsan data races in load global specializations #3187

Job	Run time
x86_64-unknown-linux-gnu/gcc	10m 55s
x86_64-apple-darwin/clang	24m 59s
x86_64-unknown-linux-gnu/gcc-free-threading	7m 36s
aarch64-apple-darwin/clang	11m 6s
aarch64-unknown-linux-gnu/gcc	7m 36s
	1h 2m 12s

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