On Fri, Jun 24, 2011 at 14:44, Rene Nussbaumer <[email protected]> wrote:
> On Fri, Jun 24, 2011 at 1:55 PM, Stephen Shirley <[email protected]> wrote:
>> diff --git a/tools/xm-console-wrapper b/tools/xm-console-wrapper
>> new file mode 100755
>> index 0000000..a5085c9
>> --- /dev/null
>> +++ b/tools/xm-console-wrapper
>> @@ -0,0 +1,33 @@
>> +#!/bin/sh
>
> Change this to /bin/bash, we're using bash everywhere :).
Heh, ok done. I had copied from tools/kvm-ifup.
>> +unpause() {
>> + ispaused=$(xm list -l "$INSTANCE" 2>/dev/null |
>> + sed -n 's/^[[:blank:]]*(state ..\(.\)...)/\1/p')
>> + [ "$ispaused" == "p" ] || return
>
> Use [[ and ]] in bash.
Also done.
>> + # Sleep to allow xm console enough time to connect
>> + sleep 3
>
> Somehow I dislike this, can we maybe use kill -0 or something to test
> if a signal is reachable and assume that when signal handling is done
> that the process is alive?
There's a few problems here. The first is that 'xm console' needs to
read/write from stdin/stdout, so it has to run in the foreground. This
means that the unpause stuff runs in the background, and doesn't know
the PID of xm console. Also i can't see any way to actually eliminate
the race condition, because we do not control xm console.
The bigger thing though is that we really just don't care. This is
intended to help with debugging of installation scripts etc, i.e. not
something for everyday use. If the machine is very heavily overloaded
and xm console hasn't already attached to the console, we'll have
missed the very beginning of the bootup, but nothing bad has happened.
If it's important to the user, they stop the instance and do it again.
To my mind the very simple (and stupid, yes) approach above covers 99%
of cases, and the 1% it doesn't cover is (a) seriously non-trivial,
and (b) going to seriously complicate stuff even trying to cover
without actually fixing it completely.
Steve
