Re: [Qemu-devel] [PATCH v4 19/47] Rework loadvm path for subloops

[Dr. David Alan Gilbert]

* David Gibson (address@hidden) wrote:
> On Wed, Nov 19, 2014 at 05:50:11PM +0000, Dr. David Alan Gilbert wrote:
> > * David Gibson (address@hidden) wrote:
> > > On Fri, Oct 03, 2014 at 06:47:25PM +0100, Dr. David Alan Gilbert (git) 
> > > wrote:
> > > > From: "Dr. David Alan Gilbert" <address@hidden>
> > > > 
> > > > Postcopy needs to have two migration streams loading concurrently;
> > > > one from memory (with the device state) and the other from the fd
> > > > with the memory transactions.
> > > > 
> > > > Split the core of qemu_loadvm_state out so we can use it for both.
> > > > 
> > > > Allow the inner loadvm loop to quit and signal whether the parent
> > > > should.
> > > > 
> > > > loadvm_handlers is made static since it's lifetime is greater
> > > > than the outer qemu_loadvm_state.
> > > 
> > > Maybe it's just me, but "made static" to me indicates either a change
> > > from fully-global to module-global, or (function) local automatic to
> > > local static, not a change from function local-automatic to
> > > module-global as here.
> > > 
> > > It's also not clear from this patch alone why the lifetime of
> > > loadvm_handlers now needs to exceed that of qemu_loadvm_state().
> > 
> > OK, how about if I reworked that last sentence to be:
> > 
> >    loadvm_handlers is made module-global to survive beyond the lifetime
> >    of the outer qemu_loadvm_state since it may still be in use by
> >    a subloop in the postcopy listen thread.
> 
> Yeah, that's better.  A global seems ugly though.  Would it be better
> to dynamically allocate the list head and pass a pointer into the
> listen thread, or even to pass the list head by value into the listen
> thread.
> 
> The individual list elements need to be cleaned up at some point
> anyway, so I don't think that introduces any lifetime questions that
> weren't already there.

I've moved the loadvm_handlers out into the MigrationIncomingState
structure, and free them when that is deallocated at the end of migration.

Dave

> 
> -- 
> David Gibson                  | I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au        | minimalist, thank you.  NOT _the_ 
> _other_
>                               | _way_ _around_!
> http://www.ozlabs.org/~dgibson


--
Dr. David Alan Gilbert / address@hidden / Manchester, UK