Make mode descriptor cache initialization thread-safe. #2351
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Initializing mode descriptor cache in-place is racy and may cause a thread to observe a partially constructed cache if another thread is pre-empted while it's still constructing the cache. In this change, the mode descriptor cache is constructed into a local variable instead and then set globally in a single atomic operation, preventing any possibility of observing an incomplete cache.
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Initializing mode descriptor cache in-place is racy and may cause a thread to
observe a partially constructed cache if another thread is pre-empted while
it's still constructing the cache. In this change, the mode descriptor cache is
constructed into a local variable instead and then set globally in a single
atomic operation, preventing any possibility of observing an incomplete cache.