Change FAQ example with race conditions #1150
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JulianKnodt
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cuviper
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cuviper
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FAQ.md
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| best_cost.store(...); | ||
| // Note: doing `best_cost.store(...)` will introduce race conditions. | ||
| // Using `fetch_*` such as `fetch_min` will help prevent race conditions. | ||
| best_cost.fetch_min(cost_so_far, Ordering::SeqCst); |
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The idea is that best_cost is a total, while cost_so_far is only partial. So the first load means "if we're already too big, give up," and then it would finish computing the current cost and eventually try to fetch_min that as the new best.
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| best_cost.fetch_min(cost_so_far, Ordering::SeqCst); | |
| best_cost.fetch_min(..., Ordering::SeqCst); |
Or we could expand the first ellipses, something like:
let total_cost = cost_so_far + ...;
best_cost.fetch_min(total_cost, Ordering::SeqCst);There was a problem hiding this comment.
Went with the first suggestion of changing fetch_min(..., Ordering::SeqCst).
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Previously this example in the FAQ as written would've introduced a race condition.
While I know the objective of this example is not to show exactly correct code, it seemed a bit odd to me since there's a whole section earlier about preventing race conditions. The last change was a while ago, so the API wasn't the same, but it would be good to update it so there's no race conditions.