Re: [Qemu-devel] [PATCH 3/6] migration: Make sure that all multifd channels have been created

[Juan Quintela <quintela@redhat.com>]

"Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> * Juan Quintela (quintela@redhat.com) wrote:
>> If we start the migration before all have been created, we have to
>> handle the case that one channel still don't exist.  This way it is
>> easier.
>> 
>> Signed-off-by: Juan Quintela <quintela@redhat.com>
>> @@ -3486,6 +3492,14 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
>>      ram_control_before_iterate(f, RAM_CONTROL_SETUP);
>>      ram_control_after_iterate(f, RAM_CONTROL_SETUP);
>>  
>> +    /* We want to wait for all threads to have started before doing
>> +     * anything else */
>> +    for (int i = 0; i < migrate_multifd_channels(); i++) {
>> +        MultiFDSendParams *p = &multifd_send_state->params[i];
>> +
>> +        qemu_sem_wait(&p->started);
>> +        trace_multifd_send_thread_started(p->id);
>> +    }
>
> What happens if there's an error during startup and either we cancel or
> the migration fails and we try and cleanup - how do we get out of this
> loop?

Good catch.

Will think a way to do it.

Thanks.


> Dave
>
>>      multifd_send_sync_main();
>>      qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
>>      qemu_fflush(f);
>> diff --git a/migration/trace-events b/migration/trace-events
>> index 886ce70ca0..dd13a5c4b1 100644
>> --- a/migration/trace-events
>> +++ b/migration/trace-events
>> @@ -95,6 +95,7 @@ multifd_send_sync_main_wait(uint8_t id) "channel %d"
>>  multifd_send_terminate_threads(bool error) "error %d"
>>  multifd_send_thread_end(uint8_t id, uint64_t packets, uint64_t pages) "channel %d packets %" PRIu64 " pages %"  PRIu64
>>  multifd_send_thread_start(uint8_t id) "%d"
>> +multifd_send_thread_started(uint8_t id) "channel %d"
>>  ram_discard_range(const char *rbname, uint64_t start, size_t len) "%s: start: %" PRIx64 " %zx"
>>  ram_load_loop(const char *rbname, uint64_t addr, int flags, void *host) "%s: addr: 0x%" PRIx64 " flags: 0x%x host: %p"
>>  ram_load_postcopy_loop(uint64_t addr, int flags) "@%" PRIx64 " %x"
>> -- 
>> 2.21.0
>> 
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK