From: Fabiano Rosas <faro...@suse.de> During multifd channel creation (multifd_send_new_channel_async) when TLS is enabled, the multifd_channel_connect function is called twice, once to create the TLS handshake thread and another time after the asynchrounous TLS handshake has finished.
This creates a slightly confusing call stack where multifd_channel_connect() is called more times than the number of channels. It also splits error handling between the two callers of multifd_channel_connect() causing some code duplication. Lastly, it gets in the way of having a single point to determine whether all channel creation tasks have been initiated. Refactor the code to move the reentrancy one level up at the multifd_new_send_channel_async() level, de-duplicating the error handling and allowing for the next patch to introduce a synchronization point common to all the multifd channel creation, regardless of TLS. Note that the previous code would never fail once p->c had been set. This patch changes this assumption, which affects refcounting, so add comments around object_unref to explain the situation. Reviewed-by: Peter Xu <pet...@redhat.com> Signed-off-by: Fabiano Rosas <faro...@suse.de> Link: https://lore.kernel.org/r/20240206215118.6171-6-faro...@suse.de Signed-off-by: Peter Xu <pet...@redhat.com> --- migration/multifd.c | 83 ++++++++++++++++++++++----------------------- 1 file changed, 40 insertions(+), 43 deletions(-) diff --git a/migration/multifd.c b/migration/multifd.c index cf865edba0..3db18dc79e 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -869,30 +869,7 @@ out: return NULL; } -static bool multifd_channel_connect(MultiFDSendParams *p, - QIOChannel *ioc, - Error **errp); - -static void multifd_tls_outgoing_handshake(QIOTask *task, - gpointer opaque) -{ - MultiFDSendParams *p = opaque; - QIOChannel *ioc = QIO_CHANNEL(qio_task_get_source(task)); - Error *err = NULL; - - if (!qio_task_propagate_error(task, &err)) { - trace_multifd_tls_outgoing_handshake_complete(ioc); - if (multifd_channel_connect(p, ioc, &err)) { - return; - } - } - - trace_multifd_tls_outgoing_handshake_error(ioc, error_get_pretty(err)); - - multifd_send_set_error(err); - multifd_send_kick_main(p); - error_free(err); -} +static void multifd_new_send_channel_async(QIOTask *task, gpointer opaque); static void *multifd_tls_handshake_thread(void *opaque) { @@ -900,7 +877,7 @@ static void *multifd_tls_handshake_thread(void *opaque) QIOChannelTLS *tioc = QIO_CHANNEL_TLS(p->c); qio_channel_tls_handshake(tioc, - multifd_tls_outgoing_handshake, + multifd_new_send_channel_async, p, NULL, NULL); @@ -920,6 +897,10 @@ static bool multifd_tls_channel_connect(MultiFDSendParams *p, return false; } + /* + * Ownership of the socket channel now transfers to the newly + * created TLS channel, which has already taken a reference. + */ object_unref(OBJECT(ioc)); trace_multifd_tls_outgoing_handshake_start(ioc, tioc, hostname); qio_channel_set_name(QIO_CHANNEL(tioc), "multifd-tls-outgoing"); @@ -936,18 +917,7 @@ static bool multifd_channel_connect(MultiFDSendParams *p, QIOChannel *ioc, Error **errp) { - trace_multifd_set_outgoing_channel( - ioc, object_get_typename(OBJECT(ioc)), - migrate_get_current()->hostname); - - if (migrate_channel_requires_tls_upgrade(ioc)) { - /* - * tls_channel_connect will call back to this - * function after the TLS handshake, - * so we mustn't call multifd_send_thread until then - */ - return multifd_tls_channel_connect(p, ioc, errp); - } + qio_channel_set_delay(ioc, false); migration_ioc_register_yank(ioc); p->registered_yank = true; @@ -959,24 +929,51 @@ static bool multifd_channel_connect(MultiFDSendParams *p, return true; } +/* + * When TLS is enabled this function is called once to establish the + * TLS connection and a second time after the TLS handshake to create + * the multifd channel. Without TLS it goes straight into the channel + * creation. + */ static void multifd_new_send_channel_async(QIOTask *task, gpointer opaque) { MultiFDSendParams *p = opaque; QIOChannel *ioc = QIO_CHANNEL(qio_task_get_source(task)); Error *local_err = NULL; + bool ret; trace_multifd_new_send_channel_async(p->id); - if (!qio_task_propagate_error(task, &local_err)) { - qio_channel_set_delay(ioc, false); - if (multifd_channel_connect(p, ioc, &local_err)) { - return; - } + + if (qio_task_propagate_error(task, &local_err)) { + ret = false; + goto out; + } + + trace_multifd_set_outgoing_channel(ioc, object_get_typename(OBJECT(ioc)), + migrate_get_current()->hostname); + + if (migrate_channel_requires_tls_upgrade(ioc)) { + ret = multifd_tls_channel_connect(p, ioc, &local_err); + } else { + ret = multifd_channel_connect(p, ioc, &local_err); } + if (ret) { + return; + } + +out: trace_multifd_new_send_channel_async_error(p->id, local_err); multifd_send_set_error(local_err); multifd_send_kick_main(p); - object_unref(OBJECT(ioc)); + if (!p->c) { + /* + * If no channel has been created, drop the initial + * reference. Otherwise cleanup happens at + * multifd_send_channel_destroy() + */ + object_unref(OBJECT(ioc)); + } error_free(local_err); } -- 2.43.0
