bug#32452: 26.1; gnutls_try_handshake maxes out cpu retrying when server is a bit busy

[Noam Postavsky]

Eli Zaretskii <eliz@gnu.org> writes:

> OK, so do you understand the sequence of the events well enough to
> describe what happens, and explain why we get so many EAGAIN errors?
> I'm not yet sure this is bug, maybe it's just how things are in this
> case (modulo exerting less CPU load, something that we certainly
> should try).

I haven't really traced things through properly, but my current
understanding/guess is that we're using non-blocking sockets even though
we actually want blocking behaviour.  So to get the blocking behaviour
we just spin in a loop.

> Also, does this happen with every server, or just with some?

debbugs.gnu.org seems to be the most extreme case (at the moment), with
other servers I see only about a hundred "Resource temporarily
unavailable" messages (I'm noticing this now because I switched on
gnutls-log-level, but it's not enough to cause a noticable CPU spike).