review: fix: Use thread-local caching for actual class lookup #4671
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slarse
changed the title
MartinWitt
approved these changes
Apr 11, 2022
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LGTM as a short-term fix. |
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thanks, @slarse |
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Fix #4668
This is a quick-fix to avoid the cross-thread race condition when invalidating the cache and then doing a lookup in it. This is a problem as the current lock is per-instance but the cache is static, so in theory a thread A could check the cache integrity and state that it's fine, then there's a context switch to thread B which does the same thing and invalidates the cache and inserts something into the cache, and then we're back to thread B which does a lookup on a "bad cache" (according to thread A's view of the world).
By using thread-local storage, this situation cannot occur.