vhost-user-test: fix chardriver race

vhost-user-tests uses a helper thread to dispatch the vhost-user servers
sources. However the CharDriverState is not thread-safe. Therefore, when
it's given to the thread, it shouldn't be manipulated concurrently.

We dispatch cleaning the server in an idle source. By the end of the
test, we ensure not to leave anything behind by joining the thread and
finishing the sources dispatch.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

tests/vhost-user-test.c

@@ -216,8 +216,7 @@ static void read_guest_mem(TestServer *s)
 
 static void *thread_function(void *data)
 {
-    GMainLoop *loop;
-    loop = g_main_loop_new(NULL, FALSE);
+    GMainLoop *loop = data;
     g_main_loop_run(loop);
     return NULL;
 }
@@ -389,7 +388,7 @@ static TestServer *test_server_new(const gchar *name)
     g_strdup_printf(QEMU_CMD extra, (mem), (mem), (root), (s)->chr_name,       \
                     (s)->socket_path, (s)->chr_name, ##__VA_ARGS__)
 
-static void test_server_free(TestServer *server)
+static gboolean _test_server_free(TestServer *server)
 {
     int i;
 
@@ -406,9 +405,15 @@ static void test_server_free(TestServer *server)
     unlink(server->socket_path);
     g_free(server->socket_path);
 
-
     g_free(server->chr_name);
     g_free(server);
+
+    return FALSE;
+}
+
+static void test_server_free(TestServer *server)
+{
+    g_idle_add((GSourceFunc)_test_server_free, server);
 }
 
 static void wait_for_log_fd(TestServer *s)
@@ -590,6 +595,8 @@ int main(int argc, char **argv)
     char *qemu_cmd = NULL;
     int ret;
     char template[] = "/tmp/vhost-test-XXXXXX";
+    GMainLoop *loop;
+    GThread *thread;
 
     g_test_init(&argc, &argv, NULL);
 
@@ -612,8 +619,9 @@ int main(int argc, char **argv)
 
     server = test_server_new("test");
 
+    loop = g_main_loop_new(NULL, FALSE);
     /* run the main loop thread so the chardev may operate */
-    g_thread_new(NULL, thread_function, NULL);
+    thread = g_thread_new(NULL, thread_function, loop);
 
     qemu_cmd = GET_QEMU_CMD(server);
 
@@ -632,6 +640,14 @@ int main(int argc, char **argv)
     /* cleanup */
     test_server_free(server);
 
+    /* finish the helper thread and dispatch pending sources */
+    g_main_loop_quit(loop);
+    g_thread_join(thread);
+    while (g_main_context_pending(NULL)) {
+        g_main_context_iteration (NULL, TRUE);
+    }
+    g_main_loop_unref(loop);
+
     ret = rmdir(tmpfs);
     if (ret != 0) {
         g_test_message("unable to rmdir: path (%s): %s\n",