(ITS#4343) WAKE_LISTENER loses wake events

[hyc@OpenLDAP.org]

Full_Name: Howard Chu
Version: 2.3,HEAD
OS: 
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (24.126.120.178)
Submitted by: hyc


This is already fixed in HEAD, just noting it here.

I recall we discussed the possibility of this being a problem in the past.
Apparently the last round if ITS#3950 changes caused it to occur more
frequently. The result being that slapd sits idle while clients wait for
responses...

WAKE_LISTENER needed a counter in non-threaded slapd to prevent the wake pipe
from filling up. But with threaded slapd, there's a race between zeroing the
counter and reading the wake pipe, so it's best to just write the pipe
unconditionally and dispense with the counter.