Re: [PATCH v1 4/4] migration/multifd: Move load_cleanup inside incoming_state_destroy

[Juan Quintela <quintela@redhat.com>]

Leonardo Bras <leobras@redhat.com> wrote:
> Currently running migration_incoming_state_destroy() without first running
> multifd_load_cleanup() will cause a yank error:
>
> qemu-system-x86_64: ../util/yank.c:107: yank_unregister_instance:
> Assertion `QLIST_EMPTY(&entry->yankfns)' failed.
> (core dumped)
>
> The above error happens in the target host, when multifd is being used
> for precopy, and then postcopy is triggered and the migration finishes.
> This will crash the VM in the target host.
>
> To avoid that, move multifd_load_cleanup() inside
> migration_incoming_state_destroy(), so that the load cleanup becomes part
> of the incoming state destroying process.
>
> Running multifd_load_cleanup() twice can become an issue, though, but the
> only scenario it could be ran twice is on process_incoming_migration_bh().
> So removing this extra call is necessary.
>
> On the other hand, this multifd_load_cleanup() call happens way before the
> migration_incoming_state_destroy() and having this happening before
> dirty_bitmap_mig_before_vm_start() and vm_start() may be a need.
>
> So introduce a new function multifd_load_shutdown() that will mainly stop
> all multifd threads and close their QIOChannels. Then use this function
> instead of multifd_load_cleanup() to make sure nothing else is received
> before dirty_bitmap_mig_before_vm_start().
>
> Signed-off-by: Leonardo Bras <leobras@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>