iothread: delay the context release to finalize

When gcontext is used with iothread, the context will be destroyed
during iothread_stop().  That's not good since sometimes we would like
to keep the resources until iothread is destroyed, but we may want to
stop the thread before that point.

Delay the destruction of gcontext to iothread finalize.  Then we can do:

  iothread_stop(thread);
  some_cleanup_on_resources();
  iothread_destroy(thread);

We may need this patch if we want to run chardev IOs in iothreads and
hopefully clean them up correctly.  For more specific information,
please see 2b316774f6 ("qemu-char: do not operate on sources from
finalize callbacks").

Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-id: 20170928025958.1420-5-peterx@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

diff --git a/iothread.c b/iothread.c
index b3c092b2d73a599d5660aa2d14b1f50094e466c7..27a42885781aa7e5bcc251be34fbc9440545d989 100644 (file)
--- a/iothread.c
+++ b/iothread.c
@@ -71,8 +71,6 @@ static void *iothread_run(void *opaque)
             g_main_loop_unref(loop);
 
             g_main_context_pop_thread_default(iothread->worker_context);
-            g_main_context_unref(iothread->worker_context);
-            iothread->worker_context = NULL;
         }
     }
 
@@ -117,6 +115,10 @@ static void iothread_instance_finalize(Object *obj)
     IOThread *iothread = IOTHREAD(obj);
 
     iothread_stop(iothread);
+    if (iothread->worker_context) {
+        g_main_context_unref(iothread->worker_context);
+        iothread->worker_context = NULL;
+    }
     qemu_cond_destroy(&iothread->init_done_cond);
     qemu_mutex_destroy(&iothread->init_done_lock);
     if (!iothread->ctx) {