h2/fix dropper #1057
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h2/fix dropper #1057
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howardjohn
commented
May 15, 2024
howardjohn
commented
- With compiler bug
- h2: remove drop counter from server
This isn't incremented on the server, and dropping it causes overflow. This is ~fine, but if trace logging is turned on we do a panic-causing overflow (I think only in debug builds?).
howardjohn
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ilrudie
reviewed
May 15, 2024
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| impl Drop for H2StreamWriteHalf { | ||
| impl Drop for DropCounter { | ||
| fn drop(&mut self) { | ||
| let mut half_dropped = Arc::new(()); | ||
| std::mem::swap(&mut self.half_dropped, &mut half_dropped); | ||
| if Arc::into_inner(half_dropped).is_none() { |
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I know you aren't changing this but it seems like this logic isn't correct... If we get none back it means we are not the last strong reference so the other half isn't dropped. If we get the inner value back we are the last strong reference.
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If we get none back it means we are not the last strong reference so the other half isn't dropped
Otherwise, [None](https://doc.rust-lang.org/std/option/enum.Option.html#variant.None) is returned and the Arc is dropped.
This will succeed even if there are outstanding weak references.
If Arc::into_inner is called on every clone of this Arc, it is guaranteed that exactly one of the calls returns the inner value. This means in particular that the inner value is not dropped.
I think this means that if an atomicbool or some other concrete value is used and wrapped with an Arc, it should be possible to write this without the swap, yeah.
bleggett
reviewed
May 15, 2024
bleggett
approved these changes
May 16, 2024
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In response to a cherrypick label: #1057 failed to apply on top of branch "release-1.22": |
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In response to a cherrypick label: new issue created for failed cherrypick: #1064 |
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