[libvirt] virsh migrate: sometimes command line cannot exit until manually press "ENTER" key

[Chun Yan Liu]

>>> On 8/8/2014 at 12:18 AM, in message
<CAAfHSJvP1P20kBFD9ZgYy=0JVvG5oiS0eVCfGZc+k39=EharkQ at mail.gmail.com>,
Shivaprasad bhat <shivaprasadbhat at gmail.com> wrote: 
> On Thu, Aug 7, 2014 at 11:02 AM, Chun Yan Liu <cyliu at suse.com> wrote: 
> > Hi, List, 
> > 
> > Do you meet the same problem? Host is kvm, doing: (e.g.) 
> > #virsh migrate sles11 qemu+ssh://147.2.207.55/system --live --unsafe 
> > password: 
> > Sometimes, VM is already running on the target host and disappears 
> > from source host, but the command line still hangs there, if pressing 
> > "ENTER", it will exit. 
> > 
> > I debugged the code, but found the result is weird. The code hangs at 
> > tools/virsh-domain.c -> cmdMigrate ->vshWatchJob->poll(): 
> > poll() is trying to select pipe_fd, which is used to receive message from 
> > doMigrate thread. In debugging, found that doMigrate finishes and at 
> > the end it  does call safewrite() to write the retval ('0' or '1') to  
> pipe_fd, 
> > and the write is completed. But cmdMigrate poll() cannot get the event. 
> > Then after pressing "ENTER" key, poll() can get the event and select 
> > pipe_fd, then command line can exit. 
> > 
> > Any ideas about the possible reason? 
>  
> It is because, the authentication thread is independently waiting for the 
> password on virsh. I see that the virWatchJob interferes with authentication 
> thread and the password is never taken successfully. The virWatchJob 
> probably needs to wait till the authentication thread completes taking the 
> password after which it should start watching the job.

Agree. Although in my testing password can be taken successfully, and I
don't know how to explain why pressing "ENTER" then poll() can get
the pipe_fd event, I do think both authentication thread and main process
uses stdin might have some bad affect.

I'd like to adjust the code a little to move the authentication before poll(). 

Thanks!
> Moreover, I see 
> that --p2p 
> migration doesnt work at all when auto login is not configured. 
>  
> > 
> > Thanks, 
> > Chunyan 
> > 
> > 
> > -- 
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>  
> Thanks, 
> Shiva 
>  
>