Bug: xm commands hanging due to poor threading in xend

[Matt Ayres <matta@tektonic.net>]

I have noticed my most major issue with putting xend into full 
production is with many xm commands being issued it hangs and only 
starts working (sometimes) after a "service xend restart".  I created a 
bug a long time for this and have attached 3 different sets of logs 
using xen-bugtool.  This happens to most servers after running for 3-4 
days.  Those that have little activity on the xend daemon (older servers 
that were upgraded) can go 2 weeks+ at this point.  Once Xen gets to 
this state even restarting xend so the list command (and others) work, 
running "xm shutdown -a"  will guarantee an internal server error from 
xend.

I've also run into this once:

Message from syslogd@vm20 at Fri Jan 20 23:16:52 2006 ...
vm20 xenstored: xenstored corruption: connection id -1: err No such file 
or directory: No child '(null)' found
Error: Error connecting to xend: Connection refused.  Is xend running?

This is all using -unstable.  There are not many commits to 3.0-testing 
specifically regarding xend/tdb/xenstore so tracking it at this point 
seems useless.

Bug url: http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=465