Always capture mutable GlobalState with as const #8792
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These `multiplexJob` calls are places where we could accidentally concurrently mutate `GlobalState`. Luckily we're not doing that in any of these places today, but I want to make sure it stays that way by explicitly using `as_const`.
froydnj
approved these changes
Apr 24, 2025
| // Unconditionally update the total to avoid starving the consumer thread | ||
| numTreesProcessed += job.numTreesProcessed; | ||
| workers.multiplexJob( | ||
| "substituteTrees", [&cgs = as_const(cgs), &logger = cgs.tracer(), batchq, resultq, cancelable]() { |
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I am on my phone, so it's hard to be 100% sure, but it looks like we don't mutate GlobalState in this function, so we could just take it as a const in this function from the start?
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I think that the earlier block is using cgs mutably (I think the earlier block is where we actually merge the GlobalStates.
That's probably worth another look just to be sure, but I think we can't change mergeIndexResults to take a const GlobalState &
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Motivation
These
multiplexJobcalls are places where we could accidentallyconcurrently mutate
GlobalState. Luckily we're not doing that in any ofthese places today, but I want to make sure it stays that way by explicitly
using
as_const.In particular, this revealed that
mergeIndexResultstechnically was using aMutableContextinstead of aContextin amultiplexJob, but we were onlycalling
constmethods (if any) onctxso it happened to be fine.Test plan
Existing tests