Re: [Qemu-devel] [PATCH 4/5] migration: fix qemu carsh when RDMA live migration

[858585 jemmy <jemmy858585@gmail.com>]

On Thu, Apr 12, 2018 at 12:43 AM, Dr. David Alan Gilbert
<dgilbert@redhat.com> wrote:
> * Lidong Chen (jemmy858585@gmail.com) wrote:
>> After postcopy, the destination qemu work in the dedicated
>> thread, so only invoke yield_until_fd_readable before postcopy
>> migration.
>
> The subject line needs to be more discriptive:
>    migration: Stop rdma yielding during incoming postcopy
>
> I think.
> (Also please check the subject spellings)
>
>> Signed-off-by: Lidong Chen <lidongchen@tencent.com>
>> ---
>>  migration/rdma.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/migration/rdma.c b/migration/rdma.c
>> index 53773c7..81be482 100644
>> --- a/migration/rdma.c
>> +++ b/migration/rdma.c
>> @@ -1489,11 +1489,13 @@ static int qemu_rdma_wait_comp_channel(RDMAContext *rdma)
>>       * Coroutine doesn't start until migration_fd_process_incoming()
>>       * so don't yield unless we know we're running inside of a coroutine.
>>       */
>> -    if (rdma->migration_started_on_destination) {
>> +    if (rdma->migration_started_on_destination &&
>> +        migration_incoming_get_current()->state == MIGRATION_STATUS_ACTIVE) {
>
> OK, that's a bit delicate; watch if it ever gets called in a failure
> case or similar - and also wathc out if we make more use of the status
> on the destination, but otherwise, and with a fix for the subject;

How about use migration_incoming_get_current()->have_listen_thread?

    if (rdma->migration_started_on_destination &&
        migration_incoming_get_current()->have_listen_thread == false) {
        yield_until_fd_readable(rdma->comp_channel->fd);
    }

>
>
> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>
>>          yield_until_fd_readable(rdma->comp_channel->fd);
>>      } else {
>>          /* This is the source side, we're in a separate thread
>>           * or destination prior to migration_fd_process_incoming()
>> +         * after postcopy, the destination also in a seprate thread.
>>           * we can't yield; so we have to poll the fd.
>>           * But we need to be able to handle 'cancel' or an error
>>           * without hanging forever.
>> --
>> 1.8.3.1
>>
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK