songgaoye opened a new pull request, #3621:
URL: https://github.com/apache/brpc/pull/3621
### What problem does this PR solve?
Issue Number: resolve
Problem Summary:
`Socket` maintains `_unwritten_bytes` as the source of truth for pending
output, but also caches the overcrowding state in a separate `volatile bool`
named `_overcrowded`.
`WriteRequest::Setup()` and `CancelUnwrittenBytes()` can update this cached
boolean concurrently with `Socket::Write()` reading it. `volatile` does not
provide synchronization, so these accesses form a C++ data race. The cached
state can also become stale when concurrent increment and decrement paths
overwrite each other.
### What is changed and the side effects?
Changed:
- Remove the `_overcrowded` cached boolean.
- Derive the overcrowding state from an atomic load of `_unwritten_bytes`.
- Use `is_overcrowded()` in write admission checks and socket debug output.
- Add unit coverage for the boundary behavior around
`-socket_max_unwritten_bytes`.
Side effects:
- Performance effects:
- Breaking backward compatibility:
---
### Check List:
- Please make sure your changes are compilable.
- When providing us with a new feature, it is best to add related tests.
- Please follow [Contributor Covenant Code of
Conduct](https://github.com/apache/brpc/blob/master/CODE_OF_CONDUCT.md).
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