IOStream read can fail if closed with an open read buffer

[minrk]

I'm currently investigating the issue mentioned here and I've narrowed the situation down somewhat:

SimpleAsyncHTTPRequest is making a POST request with an empty body to a server that is responding very quickly. In this case, it is the request to github.com to complete GitHub OAuth.

When read_until_regex is called in

• read buffer is not empty, but
• stream is closed

So a closed check is apparently occurring before the read is attempted from the existing buffer. Interestingly, #2670 introduces exactly such a premature closed check (a _try_inline_read() would succeed if attempted), but the issue still occurs in 6.0.2, prior to #2670, so there must be an additional check that's causing StreamClosedError to be raised even when the

I'm trying to provoke this with a self-contained test case that doesn't require github credentials, but haven't managed it yet. Will report back when I do.

Using curl_httpclient does not appear to exhibit this behavior.

I think this is related to #2651 in that it's another issue in 6.0 where there are races between the closed state and pending reads/writes.

[bdarnell]

This is the same as #2695, right?