Re: [Qemu-devel] [PATCH v4 05/32] migration: implement "postcopy-pause" src logic

[Peter Xu]

On Thu, Nov 30, 2017 at 10:49:45AM +0000, Dr. David Alan Gilbert wrote:
> * Peter Xu (address@hidden) wrote:
> > Now when network down for postcopy, the source side will not fail the
> > migration. Instead we convert the status into this new paused state, and
> > we will try to wait for a rescue in the future.
> > 
> > If a recovery is detected, migration_thread() will reset its local
> > variables to prepare for that.
> > 
> > Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> 
> That's still OK; you might want to consider reusing the 'pause_sem' that I
> added to MigrationStatus for the other pause case.

Yes I can.  I am just a bit worried about how these two different
features cross-affect each other.  Say, what if something tries to
execute "migrate-continue" during a postcopy network failure?  IMHO it
should not be allowed, but we don't yet have a protection so far.

So I would prefer to still separate these two semaphores.

Though I found that I can move init/destroy of the two new semaphores
(postcopy_pause_sem, postcopy_pause_rp_sem) into object init/destroy
just like what we did for pause_sem, which seems to be cleaner.  I
hope I can still keep your r-b if I do that small change.  Thanks,

-- 
Peter Xu