Re: [Xen-devel] race in xenstore?

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 27/04/2010 09:38, "Juergen Gross" <juergen.gross@xxxxxxxxxxxxxx> wrote:

> - the domU tries to read the entry, xenstored seems not to know it:
>     IN 0x61b9c0 20100423 22:25:42 READ (bs2/vmid )
>     OUT 0x61b9c0 20100423 22:25:42 ERROR (ENOENT )
> - on domU side, I don't see the ENOENT, but read the string "OK"!
> - a little bit later (same second) the entry is written by dom0:
>     IN 0x625c50 20100423 22:25:42 WRITE (/local/domain/169/bs2/vmid 2)
>     OUT 0x625c50 20100423 22:25:42 WRITE (OK )
> 
> Xen version is 3.3.1
> 
> I'm not familiar with the xenstored internals, perhaps someone has an idea
> what is happening here?

Not sure, but it would be weird for this to be a race since xenstored is
single-threaded and deals with only one request at a time, to completion.

I would focus on why xenstored logging says ENOENT, but the domU sees 'OK'.
The xenstored logic is not so hard to figure out, compared with xend for
example. ;-)

 -- Keir



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