1 files changed, 86 insertions, 4 deletions

diff --git a/chardev/char-socket.c b/chardev/char-socket.c
index 86c1f502d6..4fcdd8aedd 100644
--- a/chardev/char-socket.c
+++ b/chardev/char-socket.c
@@ -80,6 +80,8 @@ typedef struct {
     GSource *reconnect_timer;
     int64_t reconnect_time;
     bool connect_err_reported;
+
+    QIOTask *connect_task;
 } SocketChardev;
 
 #define SOCKET_CHARDEV(obj)                                     \
@@ -118,6 +120,7 @@ static void qemu_chr_socket_restart_timer(Chardev *chr)
     char *name;
 
     assert(s->state == TCP_CHARDEV_STATE_DISCONNECTED);
+    assert(!s->reconnect_timer);
     name = g_strdup_printf("chardev-socket-reconnect-%s", chr->label);
     s->reconnect_timer = qemu_chr_timeout_add_ms(chr,
                                                  s->reconnect_time * 1000,
@@ -965,7 +968,56 @@ static int tcp_chr_wait_connected(Chardev *chr, Error **errp)
         }
     }
 
-    while (!s->ioc) {
+    tcp_chr_reconn_timer_cancel(s);
+
+    /*
+     * We expect states to be as follows:
+     *
+     *  - server
+     *    - wait   -> CONNECTED
+     *    - nowait -> DISCONNECTED
+     *  - client
+     *    - reconnect == 0 -> CONNECTED
+     *    - reconnect != 0 -> CONNECTING
+     *
+     */
+    if (s->state == TCP_CHARDEV_STATE_CONNECTING) {
+        if (!s->connect_task) {
+            error_setg(errp,
+                       "Unexpected 'connecting' state without connect task "
+                       "while waiting for connection completion");
+            return -1;
+        }
+        /*
+         * tcp_chr_wait_connected should only ever be run from the
+         * main loop thread associated with chr->gcontext, otherwise
+         * qio_task_wait_thread has a dangerous race condition with
+         * free'ing of the s->connect_task object.
+         *
+         * Acquiring the main context doesn't 100% prove we're in
+         * the main loop thread, but it does at least guarantee
+         * that the main loop won't be executed by another thread
+         * avoiding the race condition with the task idle callback.
+         */
+        g_main_context_acquire(chr->gcontext);
+        qio_task_wait_thread(s->connect_task);
+        g_main_context_release(chr->gcontext);
+
+        /*
+         * The completion callback (qemu_chr_socket_connected) for
+         * s->connect_task should have set this to NULL by the time
+         * qio_task_wait_thread has returned.
+         */
+        assert(!s->connect_task);
+
+        /*
+         * NB we are *not* guaranteed to have "s->state == ..CONNECTED"
+         * at this point as this first connect may be failed, so
+         * allow the next loop to run regardless.
+         */
+    }
+
+    while (s->state != TCP_CHARDEV_STATE_CONNECTED) {
         if (s->is_listen) {
             tcp_chr_accept_server_sync(chr);
         } else {
@@ -1014,6 +1066,8 @@ static void qemu_chr_socket_connected(QIOTask *task, void *opaque)
     SocketChardev *s = SOCKET_CHARDEV(chr);
     Error *err = NULL;
 
+    s->connect_task = NULL;
+
     if (qio_task_propagate_error(task, &err)) {
         tcp_chr_change_state(s, TCP_CHARDEV_STATE_DISCONNECTED);
         check_report_connect_error(chr, err);
@@ -1028,6 +1082,20 @@ cleanup:
     object_unref(OBJECT(sioc));
 }
 
+
+static void tcp_chr_connect_client_task(QIOTask *task,
+                                        gpointer opaque)
+{
+    QIOChannelSocket *ioc = QIO_CHANNEL_SOCKET(qio_task_get_source(task));
+    SocketAddress *addr = opaque;
+    Error *err = NULL;
+
+    qio_channel_socket_connect_sync(ioc, addr, &err);
+
+    qio_task_set_error(task, err);
+}
+
+
 static void tcp_chr_connect_client_async(Chardev *chr)
 {
     SocketChardev *s = SOCKET_CHARDEV(chr);
@@ -1036,9 +1104,23 @@ static void tcp_chr_connect_client_async(Chardev *chr)
     tcp_chr_change_state(s, TCP_CHARDEV_STATE_CONNECTING);
     sioc = qio_channel_socket_new();
     tcp_chr_set_client_ioc_name(chr, sioc);
-    qio_channel_socket_connect_async(sioc, s->addr,
-                                     qemu_chr_socket_connected,
-                                     chr, NULL, chr->gcontext);
+    /*
+     * Normally code would use the qio_channel_socket_connect_async
+     * method which uses a QIOTask + qio_task_set_error internally
+     * to avoid blocking. The tcp_chr_wait_connected method, however,
+     * needs a way to synchronize with completion of the background
+     * connect task which can't be done with the QIOChannelSocket
+     * async APIs. Thus we must use QIOTask directly to implement
+     * the non-blocking concept locally.
+     */
+    s->connect_task = qio_task_new(OBJECT(sioc),
+                                   qemu_chr_socket_connected,
+                                   chr, NULL);
+    qio_task_run_in_thread(s->connect_task,
+                           tcp_chr_connect_client_task,
+                           s->addr,
+                           NULL,
+                           chr->gcontext);
 }
 
 static gboolean socket_reconnect_timeout(gpointer opaque)