Re: Timing out waiting for vbd device *only when xend started with trace_start*

[Charles Duffy <cduffy@spamcop.net>]

Ewan Mellor wrote:
> Thanks for that.  Both you and Friedmund Lassmann are seeing the same bug.  If
> you look, you have a line from xenstored-trace.log:
> 
> OUT 0x1208c548 02:29:59 WATCH_EVENT (/local/domain/0/backend/vif/1/0 363717120 )
> 
> which is the firing of the watch, but the line from xend.log:
> 
> [2005-11-14 02:31:59 xend] DEBUG (DevController:286) hotplugStatus entered
> 
> doesn't execute until 2 minutes later, when the other thread times out.  In
> other words, I think that the waiting thread has hold of a lock, and so the
> thread waiting to deliver the watch is locked out.  I can't find that lock
> though, and I still can't reproduce this!  If either of you can get a hold on
> the problem, then that would be great.

Hmmm.

It might be nice if the xend trace handler were expanded to print both 
current PID (or thread name) and timestamp when indicating that a line 
is being executed. Not something I have time to do right now -- and 
other people are prone to using the host in question during business 
hours -- but I'll take a shot at it tomorrow morning if time permits and 
nobody else has beat me to it.

That said, the only lock I see being handled closely prior to this 
occurance is xslock in xenstore/xswatch.py:watchStart.