[Xen-devel] Help with Guest creation problem

[Mick Jordan <Mick.Jordan@xxxxxxx>]

This problem is a bit out of the mainstream as it relates to guests that 
terminate quickly, which the typical OS guest does not do, but my Java 
guest applications sometimes do.
The problem manifests itself as the behavior below. I believe that the 
cause is some race between the guest terminating, console output and the 
xm code. I'm no Python expert but it doesn't look as if the error 
handling in do_console is working correctly. Note that if the guest is 
made to sleep for a second before terminating, this behavior never happens.
I've experienced this occasionally on Solaris xVM and very frequently on 
various flavors of Xen/Linux.
Any insight appreciated.

Mick

# xm create -c xmconfigs/domain_config_generic extra= 
-XX:SemiSpaceGC:Virtual   -cp /guestvm/image/GuestVM/bin 
test.java.lang.Null  name=GuestVM-test.java.lang.Null-mjj
Unexpected error: <type 'exceptions.OSError'>

Please report to xen-devel@xxxxxxxxxxxxxxxxxxx
Traceback (most recent call last):
 File "/usr/sbin/xm", line 10, in <module>
   main.main(sys.argv)
 File "/usr/lib64/python2.5/site-packages/xen/xm/main.py", line 2500, 
in main
   _, rc = _run_cmd(cmd, cmd_name, args)
 File "/usr/lib64/python2.5/site-packages/xen/xm/main.py", line 2524, 
in _run_cmd
   return True, cmd(args)
 File "<string>", line 1, in <lambda>
 File "/usr/lib64/python2.5/site-packages/xen/xm/main.py", line 1302, 
in xm_importcommand
   cmd.main([command] + args)
 File "/usr/lib64/python2.5/site-packages/xen/xm/create.py", line 1293, 
in main
   do_console(sxp.child_value(config, 'name', -1))
 File "/usr/lib64/python2.5/site-packages/xen/xm/create.py", line 1318, 
in do_console
   (p, rv) = os.waitpid(cpid, os.WNOHANG)
OSError: [Errno 10] No child processes
[root@diy-3-15 GuestVMNative]#

create.py:

def do_console(domain_name):
   cpid = os.fork()
   if cpid != 0:
       for i in range(10):
           # Catch failure of the create process
           time.sleep(1)
           (p, rv) = os.waitpid(cpid, os.WNOHANG)
           if os.WIFEXITED(rv):
               if os.WEXITSTATUS(rv) != 0:
                   sys.exit(os.WEXITSTATUS(rv))
           try:
               # Acquire the console of the created dom
               if serverType == SERVER_XEN_API:
                   domid = server.xenapi.VM.get_domid(
                              get_single_vm(domain_name))
               else:
                   dom = server.xend.domain(domain_name)
                   domid = int(sxp.child_value(dom, 'domid', '-1'))
               console.execConsole(domid)
           except:
               pass
       print("Could not start console\n");
       sys.exit(0)


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