Re: [Xen-devel] [PATCH] libxl: prevent xl from running if xend is running.

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Ian Jackson escribió:
> Ian Campbell writes ("Re: [Xen-devel] [PATCH] libxl: prevent xl from running if xend 
>       is running."):
> > On Tue, 2012-04-24 at 14:17 +0100, Ian Jackson wrote:
> > > Can we somehow limit this to commands that actually change things ?
> > > Having xl as a diagnostic tool even for xend-based systems is useful.
> > Perhaps a new flag in xl_cmdtable.h? Overriden by -f or -N (dry run).
> Yes, something like that.
Do you mean to add a new "-f" option to each command that performs 
modifications, or modifying the cmd_spec struct to add something like 
"int modifies", and check that before trying to execute the command?
> > > > +        if (!access(locks[i], F_OK)&&  !force_execution) {
> > > > +            fprintf(stderr, "xend is running, which prevents xl from working "
> > > > +                            "correctly. If you still want to force the "
> > > > +                            "execution of xl please use the -f option\n");
> > > > +            exit(2);
> > > > +        }
> > > If access fails with an unexpected error code (EACCES? EIO?) this will
> > > blunder on.
> > It'll fail whether the error code is expected or not, won't it?
> I think if access fails with EIO, it will return -1, and the if
> condition will not be satisfied (!-1 = 0), so the fprintf and exit
> will not be taken.
>
> Ian.

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