Re: [PATCH v7 5/5] migration: add MULTIFD_RECV_SYNC migration command

[Fabiano Rosas <farosas@suse.de>]

Peter Xu <peterx@redhat.com> writes:

> On Fri, Mar 07, 2025 at 05:15:03PM +0530, Prasad Pandit wrote:
>> diff --git a/migration/migration.c b/migration/migration.c
>> index 65fc4f5eed..da2c49c303 100644
>> --- a/migration/migration.c
>> +++ b/migration/migration.c
>> @@ -3401,9 +3401,10 @@ static MigIterateState
>> migration_iteration_run(MigrationState *s)
>>      if (!in_postcopy && must_precopy <= s->threshold_size
>>          && can_switchover && qatomic_read(&s->start_postcopy)) {
>>          if (migrate_multifd()) {
>> -            multifd_send_flush();
>> -            multifd_send_sync_main(MULTIFD_SYNC_LOCAL);
>> -            qemu_savevm_send_multifd_recv_sync(s->to_dst_file);
>> +/*          multifd_send_flush();
>> + *          multifd_send_sync_main(MULTIFD_SYNC_ALL);
>> + *          qemu_savevm_send_multifd_recv_sync(s->to_dst_file);
>> + */
>> +            qemu_savevm_state_complete_multifd(s->to_dst_file);
>>              multifd_send_shutdown();
>
> Forgot to mention one thing:
>
> If you do flush and sync, IMHO we can keep the threads there and remove
> this shutdown, as long as we are sure it'll be properly shutdown when
> cleanup.
>
> With the assertion in dest threads, I think it should be OK.

Good point. Shutdown at random places makes it difficult to protect
against cleanup races.