Re: [libvirt] [PATCH libvirt v2 1/9] virConnectRegisterCloseCallback: Cleanup 'opaque' if there is no connectRegisterCloseCallback

On Mon, Jun 04, 2018 at 06:25 PM +0200, "Daniel P. Berrangé" <berrange(a)redhat.com&gt; wrote: > On Thu, Apr 26, 2018 at 08:16:54PM -0400, John Ferlan wrote:

> > If the application wants to access 'opaque' outside the context of the > callback function, it must take steps to ensure it is still alive in > whatever thread it using it. This implies the data passed for 'opaque' > should be ref-counted and they must hold a reference for their own > usage, separately from the reference assoicated with the callback that > will be released by @freecb. > > That all said, we could take a slightly different approach if we want > to be paranoid about this > > eg move the > > virConnectCloseCallbackDataPtr closeCallback; > > out of the driver specific private structs, and put it in the main > struct _virConnect instead. This sound like a revert of commit “close callback: move it to driver” (88f09b75eb99415c). Shall we really do this?

> > The main libvirt-host.c can add the callback to this itself. THe > driver code only needs to worry about actually invoking the callback > > That would allow us to have freecb() called at the right time for > all drivers, even if they don't ever use the close callback. > >> >> I'm still not sure I understand why the API cannot return a failure, but >> Daniel says it cannot. > > It can break existing applications using hypervisors that don't > implement this API, becasue its a change in behaviour. In retrospect > I wouldn't have written the API in this way today, but we must live > with the design we have. > > > Regards, > Daniel > -- > |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| > |: https://libvirt.org -o- https://fstop138.berrange.com :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| > -- Beste Grüße / Kind regards Marc Hartmayer IBM Deutschland Research & Development GmbH Vorsitzende des Aufsichtsrats: Martina Koederitz Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen Registergericht: Amtsgericht Stuttgart, HRB 243294