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

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

Ian Campbell escribiÃ:
> On Tue, 2012-04-24 at 15:47 +0100, Ian Jackson wrote:
> > Ian Campbell writes ("Re: [Xen-devel] [PATCH] libxl: prevent xl from running if xend 
> >       is running."):
> > > You could consider this to be a best effort check for xend. IOW we try
> > > and look but if we can't tell then we assume it is not.
> > I guess.
> >
> > > It's not terribly robust to just blunder on, but on the other hand being
> > > more robust has a bigger risk of false positives, e.g. failing to start
> > > xl because /var/lock/subsys/ does not exist isn't especially helpful
> > > either (the EACCESS return code doesn't distinguish that
> > > from /var/lock/subsys/xend not existing).
> > EACCES would happen only if the permissions prevented us from
> > looking.  If /var/lock/subsys doesn't exist we'll get ENOENT, the
> > "good" error return.
> Oh, right.
>
> Well, not starting because the perms on /var/lock/subsys are too tight
> (e.g. selinux restricting it to initscripts only? unrealistic maybe)
> seems unhelpful too.
>
> (I admit this isn't as compelling as my previous example).
>
> Ian.
What have we decided at the end? Should I do an inverse check, and run 
only if access(...) != 0 && errno == ENOENT?
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