Re: [Xen-devel] xenstored memory leak

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

Juergen Gross writes ("Re: [Xen-devel] xenstored memory leak"):
> On 13/07/16 14:40, Andrew Cooper wrote:
> > On 13/07/16 13:21, Juergen Gross wrote:
> >> I'll post a qemu patch to remove those watches on exit soon.

I don't think this is right.  qemu should not explictly remove watches
when it is exiting.  The cleanup should be handled by xenstored
directly (if qemu is connecting via a socket) or by the OS xenbus
driver (otherwise).  Each of those entities keeps a list of which of
their clients owns what watches.

> > That is good, but there needs to be further consideration as to how to
> > clean up after a crashed qemu/etc.
> 
> Hmm, I see two possibilities:
> 
> a) Add a possibility to do xs_unwatch() with a path and a token with
>    wildcards (e.g.: xs_unwatch(xs, "/local/domain/0/backend/qdisk",
>    "be:*:97:*") for removing all qdisk watches for domid 97) and use
>    this when doing the xenstore cleanup from libxl on domain
>    destruction.
> 
> b) Instead of watching /local/domain/<dm-domid>/backend/<type> let qemu
>    create /local/domain/<dm-domid>/backend/<type>/<domid> and watch
>    this. When this directory is being removed by libxl all the watches
>    will be gone automatically.

This is going in entirely the wrong direction.

Ian.

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