Dovecot 2.3.0 imap-login using 100% CPU

[Timo Sirainen]

On 10 Jan 2018, at 17.28, Jason Kiniry <jason at cpanel.net> wrote:
> 
> When in the process of testing out the 2.3.0 version of Dovecot, we noticed that on a busy server, imap-login can sometimes take 100% CPU and remain there indefinitely. We grabbed a gdb trace while it was happening:
> 
> dovenull 36053 31.2  0.0  60460 17316 ?        R    04:38  11:55 dovecot/imap-login
> root at server [~]# strace -p 36053
> Process 36053 attached
> ^CProcess 36053 detached

So it's not doing any syscalls. What about ltrace -tt -e '*' -p <pid>?

Also what's your doveconf -n? Mainly wondering about service imap-login { .. } settings. Probably service_count=1 (default)? This somehow hangs here when there's a client with pending input, but auth process wasn't yet connected to. It's not very obvious though how it could have gotten stuck in there.