Use one atomic operation in (*Cache).decreaseSize #7786
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| atomic.StoreUint64(&c.size, size-delta) | ||
| // Since there isn't an explicit atomic operation for subtraction, | ||
| // use addition and overflow to effectively subtract delta from c.size. | ||
| atomic.AddUint64(&c.size, math.MaxUint64-delta+1) |
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nit: I think this is still correct, but the docs suggest a slightly shorter version:
atomic.AddUint64(&c.size, ^(delta-1))
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I overlooked that in the docs. I just pushed an amended commit to use that approach.
The previous implementation was susceptible to a race condition (of correctness) since c.decreaseSize is called without a lock in (*Cache).WriteMulti. There were already tests which asserted the correctness of the result of decreaseSize, so no tests were added or modified.
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The previous implementation was susceptible to a race condition (of
correctness) since c.decreaseSize is called without a lock in
(*Cache).WriteMulti.
There were already tests which asserted the correctness of the result of
decreaseSize, so no tests were added or modified.