Fix potential concurrent hash access race condition #5299
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Currently two threads can read null from the $resolved hash and both end up trying to resolve the same thing. This restores the original lock protect scope from before 95fb926 to ensure read and write don't have a race condition.
There should be no need for the loading mechanism to always block the resolve mechanism. This gives the $resolved hash its own lock instead of using the lock for the $loaded hash.
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patrickbkr
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Jun 28, 2023
| $resolved-lock.protect: { | ||
| nqp::ifnull( | ||
| nqp::atkey($resolved,$serialized-id), | ||
| nqp::bindkey($resolved,$serialized-id, do { |
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I think this would be less convoluted when changing the do {} to nqp::stmts() (or a block) and moving the nqp::bindkey after the return False.
(Or I miss the point. :-P)
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Honestly I would be surprised if all the nqp stuff here was worth it. This is not code that runs tens of thousands of times.
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This fixes a potential race condition in
CompUnit::PrecompilationRepositorywhere two threads could race each other to read and write to a hash.