From a1af605bd5ade1a6dd571f553a6746b97f3d6869 Mon Sep 17 00:00:00 2001 From: Chuan Zheng Date: Fri, 6 Nov 2020 14:24:53 +0800 Subject: [PATCH] migration/multifd: fix hangup with TLS-Multifd due to blocking handshake MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Suggested-by: Daniel P. Berrangé Signed-off-by: Chuan Zheng Message-Id: <1604643893-8223-1-git-send-email-zhengchuan@huawei.com> Reviewed-by: Daniel P. Berrangé Signed-off-by: Dr. David Alan Gilbert --- migration/multifd.c | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-) diff --git a/migration/multifd.c b/migration/multifd.c index 68b171fb61..88486b90d6 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, -- 2.11.0