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runtime: missing page mark in write barrier #39432
There are two places in the runtime where we set mark bits:
I found this by chance when I was reorganizing these two functions. I'm fairly certainly this has been a bug since page marks were introduced in Go 1.12.
Ah! I was wrong. This is a performance bug, but not in fact a correctness bug.
The page sweeper uses the span marks to determine where it thinks sweeping will return whole spans, but it just calls