migration/multifd: Join the TLS thread

We're currently leaking the resources of the TLS thread by not joining
it and also overwriting the p->thread pointer altogether.

Fixes: a1af605bd5 ("migration/multifd: fix hangup with TLS-Multifd due to blocking handshake")
Cc: qemu-stable <qemu-stable@nongnu.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240206215118.6171-2-farosas@suse.de
Signed-off-by: Peter Xu <peterx@redhat.com>
diff --git a/migration/multifd.c b/migration/multifd.c
index fbdb129..5551711 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -630,6 +630,10 @@
     for (i = 0; i < migrate_multifd_channels(); i++) {
         MultiFDSendParams *p = &multifd_send_state->params[i];
 
+        if (p->tls_thread_created) {
+            qemu_thread_join(&p->tls_thread);
+        }
+
         if (p->running) {
             qemu_thread_join(&p->thread);
         }
@@ -921,7 +925,9 @@
     trace_multifd_tls_outgoing_handshake_start(ioc, tioc, hostname);
     qio_channel_set_name(QIO_CHANNEL(tioc), "multifd-tls-outgoing");
     p->c = QIO_CHANNEL(tioc);
-    qemu_thread_create(&p->thread, "multifd-tls-handshake-worker",
+
+    p->tls_thread_created = true;
+    qemu_thread_create(&p->tls_thread, "multifd-tls-handshake-worker",
                        multifd_tls_handshake_thread, p,
                        QEMU_THREAD_JOINABLE);
     return true;
diff --git a/migration/multifd.h b/migration/multifd.h
index 78a2317..720c9d5 100644
--- a/migration/multifd.h
+++ b/migration/multifd.h
@@ -73,6 +73,8 @@
     char *name;
     /* channel thread id */
     QemuThread thread;
+    QemuThread tls_thread;
+    bool tls_thread_created;
     /* communication channel */
     QIOChannel *c;
     /* is the yank function registered */