Description of problem:
Recently I started getting this;
apcupsd FATAL ERROR in newups.c at line 62 Mutex lock failure. ERR=Invalid argument
apcupsd FATAL ERROR in newups.c at line 100 Mutex lock failure. ERR=Invalid argument

Version-Release number of selected component (if applicable):
apcupsd-3.14.0-4.el5

How reproducible:
random

Steps to Reproduce:
1. run apcupsd (connected via USB to a SMT series APC UPS)
2. run gapcmon on another host (my workstation) to monitor the UPSes (there are two UPSes)
3. notice that one or both report communication error every once in a while (multiple days between occurrences)
  
Actual results:
[root@qnap named]# grep apcupsd\ FATAL /var/log/messages*
/var/log/messages:Apr 14 19:34:54 qnap apcupsd[3064]: apcupsd FATAL ERROR in newups.c at line 62 Mutex lock failure. ERR=Invalid argument 
/var/log/messages:Apr 14 19:34:54 qnap apcupsd[3064]: apcupsd FATAL ERROR in newups.c at line 100 Mutex lock failure. ERR=Invalid argument 
/var/log/messages.1:Apr  4 16:52:28 qnap apcupsd[25348]: apcupsd FATAL ERROR in newups.c at line 100 Mutex lock failure. ERR=Invalid argument 
/var/log/messages.1:Apr  4 16:52:28 qnap apcupsd[25348]: apcupsd FATAL ERROR in newups.c at line 62 Mutex lock failure. ERR=Invalid argument 
/var/log/messages.1:Apr  4 16:52:28 qnap apcupsd[25348]: apcupsd FATAL ERROR in newups.c at line 100 Mutex lock failure. ERR=Invalid argument 
/var/log/messages.2:Mar 30 15:51:45 qnap apcupsd[3015]: apcupsd FATAL ERROR in newups.c at line 100 Mutex lock failure. ERR=Invalid argument 
/var/log/messages.2:Mar 30 15:51:45 qnap apcupsd[3015]: apcupsd FATAL ERROR in newups.c at line 100 Mutex lock failure. ERR=Invalid argument 
/var/log/messages.2:Mar 30 15:51:45 qnap apcupsd[3015]: apcupsd FATAL ERROR in newups.c at line 62 Mutex lock failure. ERR=Invalid argument 
/var/log/messages.2:Mar 30 15:51:45 qnap apcupsd[3015]: apcupsd FATAL ERROR in newups.c at line 100 Mutex lock failure. ERR=Invalid argument 
/var/log/messages.2:Mar 30 15:51:47 qnap apcupsd[3015]: apcupsd FATAL ERROR in newups.c at line 62 Mutex lock failure. ERR=Invalid argument 
/var/log/messages.2:Mar 30 15:51:47 qnap apcupsd[3015]: apcupsd FATAL ERROR in newups.c at line 100 Mutex lock failure. ERR=Invalid argument 
[root@qnap named]# cat /etc/redhat-release 
CentOS release 5.6 (Final)
[root@qnap named]# rpm -q apcupsd
apcupsd-3.14.0-4.el5
[root@qnap named]# uname -a
Linux qnap.internal.paranoid.com 2.6.18-238.5.1.el5 #1 SMP Fri Apr 1 18:42:32 EDT 2011 i686 i686 i386 GNU/Linux
[root@qnap named]# 


[root@router ~]# grep apcupsd\ FATAL /var/log/messages*
/var/log/messages.2:Mar 29 23:32:04 router apcupsd[3117]: apcupsd FATAL ERROR in newups.c at line 62 Mutex lock failure. ERR=Invalid argument 
/var/log/messages.2:Mar 29 23:32:04 router apcupsd[3117]: apcupsd FATAL ERROR in newups.c at line 100 Mutex lock failure. ERR=Invalid argument 
/var/log/messages.2:Mar 31 11:08:42 router apcupsd[20697]: apcupsd FATAL ERROR in newups.c at line 62 Mutex lock failure. ERR=Invalid argument 
/var/log/messages.2:Mar 31 11:08:42 router apcupsd[20697]: apcupsd FATAL ERROR in newups.c at line 100 Mutex lock failure. ERR=Invalid argument 
[root@router ~]# cat /etc/redhat-release 
CentOS release 5.6 (Final)
[root@router ~]# rpm -q apcupsd
apcupsd-3.14.0-4.el5
[root@router ~]# uname -a
Linux router.internal.paranoid.com 2.6.18-238.5.1.el5 #1 SMP Fri Apr 1 18:42:32 EDT 2011 i686 i686 i386 GNU/Linux


Expected results:
apcupsd continues running.

Additional info:
In December in only had the one UPS connected to the machine 'qnap'. In March, the second UPS was delivered and connected to the machine called 'router'.
I noticed the first crash a couple weeks ago. But since apcupsd has not been updated since December, either something else changed on both machines, or I missed previous crashes (doubtful, but not excluded as I only started using gapcmon on my workstation recently). While I doubt the addition of a second UPS has anything to do with the daemon crashing (both machines do not query each other), I figured it was worth mentioning.

[root@qnap named]# rpm -q --queryformat "%{name}-%{version}-%{release} was installed on %{INSTALLTIME:date}\n" apcupsd
apcupsd-3.14.0-4.el5 was installed on Tue 07 Dec 2010 19:28:14 EET

[root@router ~]# rpm -q --queryformat "%{name}-%{version}-%{release} was installed on %{INSTALLTIME:date}\n" apcupsd
apcupsd-3.14.0-4.el5 was installed on Tue 29 Mar 2011 10:54:36 AM EEST