(ITS#6335) syncprov modtarget deadlock

[rein@OpenLDAP.org]

Full_Name: Rein Tollevik
Version: CVS HEAD
OS: linux
URL: 
Submission from: (NULL) (2a01:600:0:1:21c:23ff:feab:61cd)
Submitted by: rein


A fix for a syncprov modtarget deadlock is coming.  I have only
seen this happen once, during shutdown of one of the servers in
test058, but I'm uncertain as to whether the shutdown condition
was coincidental or not.  It is probably the same deadlock as
reported by Aaron Richton during 2.4.19 testing.

It looks as if syncprov was hanging waiting for a lock no-one
held, possibly as a result of another thread removing the
modtarget before or while it tried to acquire the modtarget
mutex.  If this is actually true, and if so why the lock and/or
destroy calls didn't fail beats me...  Anyhow, with this patch I
have had test058 running without hanging for more than a week
now.

Rein Tollevik
Basefarm AS