Re: [Xen-devel] [PATCH 3/3] libxl: Domain destroy: fork

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Mar 17, 2015 at 09:30:59AM -0600, Jim Fehlig wrote:
> From: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> 
> Call xc_domain_destroy in a subprocess.  That allows us to do so
> asynchronously, rather than blocking the whole process calling libxl.
> 
> The changes in detail:
> 
>  * Provide an libxl__ev_child in libxl__domain_destroy_state, and
>    initialise it in libxl__domain_destroy.  There is no possibility
>    to `clean up' a libxl__ev_child, but there need to clean it up, as
>    the control flow ensures that we only continue after the child has
>    exited.
> 
>  * Call libxl__ev_child_fork at the right point and put the call to
>    xc_domain_destroy and associated logging in the child.  (The child
>    opens a new xenctrl handle because we mustn't use the parent's.)
> 
>  * Consequently, the success return path from domain_destroy_domid_cb
>    no longer calls dis->callback.  Instead it simply returns.
> 
>  * We plumb the errorno value through the child's exit status, if it
>    fits.  This means we normally do the logging only in the parent.
> 
>  * Incidentally, we fix the bug that we were treating the return value
>    from xc_domain_destroy as an errno value when in fact it is a
>    return value from do_domctl (in this case, 0 or -1 setting errno).
> 
> Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
> Reviewed-by: Jim Fehlig <jfehlig@xxxxxxxx>
> Tested-by: Jim Fehlig <jfehlig@xxxxxxxx>

Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>

One nit below.

> ---
[...]
> +        ctx->xch = xc_interface_open(ctx->lg,0,0);
> +        if (!ctx->xch) goto badchild;
> +
> +        rc = xc_domain_destroy(ctx->xch, domid);
> +        if (rc < 0) goto badchild;
> +        _exit(0);
> +
> +    badchild:
> +        if (errno > 0  && errno < 126) {
> +            _exit(errno);
> +        } else {
> +            LOGE(ERROR,
> + "xc_domain_destroy failed for %d (with difficult errno value %d)",

Indentation is wrong.

Wei.

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