* Chuan Zheng ([email protected]) wrote:
> The qemu main loop could hang up forever when we enable TLS+Multifd.
> The Src multifd_send_0 invokes tls handshake, it sends hello to sever
> and wait response.
> However, the Dst main qemu loop has been waiting recvmsg() for multifd_recv_1.
> Both of Src and Dst main qemu loop are blocking and waiting for reponse which
> results in hanging up forever.
>
> Src: (multifd_send_0) Dst:
> (multifd_recv_1)
> multifd_channel_connect
> migration_channel_process_incoming
> multifd_tls_channel_connect
> migration_tls_channel_process_incoming
> multifd_tls_channel_connect
> qio_channel_tls_handshake_task
> qio_channel_tls_handshake
> gnutls_handshake
> qio_channel_tls_handshake_task
> ...
> qcrypto_tls_session_handshake
> ...
> gnutls_handshake
> ...
> ...
> ...
> recvmsg (Blocking I/O waiting for response)
> recvmsg (Blocking I/O waiting for response)
>
> Fix this by offloadinig handshake work to a background thread.
>
> Reported-by: Yan Jin <[email protected]>
> Suggested-by: Daniel P. Berrangé <[email protected]>
> Signed-off-by: Chuan Zheng <[email protected]>
Queued
> ---
> migration/multifd.c | 23 +++++++++++++++++------
> 1 file changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/migration/multifd.c b/migration/multifd.c
> index 68b171f..88486b9 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -739,6 +739,19 @@ static void multifd_tls_outgoing_handshake(QIOTask *task,
> multifd_channel_connect(p, ioc, err);
> }
>
> +static void *multifd_tls_handshake_thread(void *opaque)
> +{
> + MultiFDSendParams *p = opaque;
> + QIOChannelTLS *tioc = QIO_CHANNEL_TLS(p->c);
> +
> + qio_channel_tls_handshake(tioc,
> + multifd_tls_outgoing_handshake,
> + p,
> + NULL,
> + NULL);
> + return NULL;
> +}
> +
> static void multifd_tls_channel_connect(MultiFDSendParams *p,
> QIOChannel *ioc,
> Error **errp)
> @@ -754,12 +767,10 @@ static void
> multifd_tls_channel_connect(MultiFDSendParams *p,
>
> trace_multifd_tls_outgoing_handshake_start(ioc, tioc, hostname);
> qio_channel_set_name(QIO_CHANNEL(tioc), "multifd-tls-outgoing");
> - qio_channel_tls_handshake(tioc,
> - multifd_tls_outgoing_handshake,
> - p,
> - NULL,
> - NULL);
> -
> + p->c = QIO_CHANNEL(tioc);
> + qemu_thread_create(&p->thread, "multifd-tls-handshake-worker",
> + multifd_tls_handshake_thread, p,
> + QEMU_THREAD_JOINABLE);
> }
>
> static bool multifd_channel_connect(MultiFDSendParams *p,
> --
> 1.8.3.1
>
>
--
Dr. David Alan Gilbert / [email protected] / Manchester, UK
