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thread-safe Xend and xm commands?
Are xend and xm commands thread-safe?

Eg: Can two threads call same xm command simultaneously without causing
problems?

Thanks.

Amitabh



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RE: thread-safe Xend and xm commands? [ In reply to ]
> Are xend and xm commands thread-safe?
>
> Eg: Can two threads call same xm command simultaneously
> without causing
> problems?

Good question. I think xend tries to serializes requests, but I doubt
this has been tested much. Mike Wray can probably give a definitive
answer.

Its certainly something that has been thought about for the design of
the new tools.

Ian

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Re: thread-safe Xend and xm commands? [ In reply to ]
Ian Pratt wrote:
>>Are xend and xm commands thread-safe?
>>
>>Eg: Can two threads call same xm command simultaneously
>>without causing
>>problems?
>
>
> Good question. I think xend tries to serializes requests, but I doubt
> this has been tested much. Mike Wray can probably give a definitive
> answer.

Xend itself is single-threaded - so it can only do one command at a time.
Some commands result in long-lived actions so there is potential for
conflict, but the obvious ones are OK as far as I know.

For example, you can tell a domain to reboot and then shut it down without
reboot or destroy it while the reboot is in progress. Xend will then
cancel the reboot.

Did you have any specific xm commands you were wondering about?

>
> Its certainly something that has been thought about for the design of
> the new tools.
>
> Ian

Mike


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Re: thread-safe Xend and xm commands? [ In reply to ]
I am thinking of calling the xm commands on two different domains in
different threads.

Each thread is responsible for managing a separate domain. So, is it safe to
call two xm commands (same or different) for different domains in different
threads?

The specific xm commands that I have in mind are:
xm create
xm shutdown
xm destroy
xm list
xm --live migrate
xm save
xm restore

One thread might be calling `xm destroy` and other thread might be calling
`xm list` or any other combination.

Thank you,

Amitabh


From: Mike Wray <mike.wray@hpl.hp.com>
To: Ian Pratt <m+Ian.Pratt@cl.cam.ac.uk>
CC: Amitabh Tamhane <amitabh_2k@hotmail.com>,xen-users@lists.xensource.com,
ian.pratt@cl.cam.ac.uk
Subject: Re: [Xen-users] thread-safe Xend and xm commands?
Date: Tue, 29 Mar 2005 09:52:11 +0100

Ian Pratt wrote:
>>Are xend and xm commands thread-safe?
>>
>>Eg: Can two threads call same xm command simultaneously without causing
>>problems?
>
>
>Good question. I think xend tries to serializes requests, but I doubt
>this has been tested much. Mike Wray can probably give a definitive
>answer.

Xend itself is single-threaded - so it can only do one command at a time.
Some commands result in long-lived actions so there is potential for
conflict, but the obvious ones are OK as far as I know.

For example, you can tell a domain to reboot and then shut it down without
reboot or destroy it while the reboot is in progress. Xend will then
cancel the reboot.

Did you have any specific xm commands you were wondering about?

>
>Its certainly something that has been thought about for the design of
>the new tools.
>
>Ian

Mike



Amitabh P. Tamhane

'THERE IS NO SHORT-CUT TO SUCCESS!'



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