On Thu, Dec 14, 2017 at 01:43:59PM +0000, Stefan Hajnoczi wrote:
> On Tue, Dec 05, 2017 at 01:51:55PM +0800, Peter Xu wrote:
> > @@ -4429,6 +4515,13 @@ void monitor_cleanup(void)
> > */
> > iothread_stop(mon_global.mon_iothread);
> >
> > + /*
> > + * After we have IOThread to send responses, it's possible that
> > + * when we stop the IOThread there are still replies queued in the
> > + * responder queue. Flush all of them.
> > + */
> > + monitor_qmp_bh_responder(NULL);
>
> This doesn't work because monitor_qmp_bh_responder() does not guarantee
> that the full response has been written when it returns.
>
> When qemu_chr_fe_write() returns EAGAIN then qemu_chr_fe_add_watch() is
> used to register an event loop callback when the chardev becomes
> writable again. But you stopped the event loop using iothread_stop() so
> we will never complete the write.
Good catch...
Actually I just noticed that for char frontend I missed a place to use
the chardev context for polling. So before the flushing I possibly
need this:
diff --git a/chardev/char-fe.c b/chardev/char-fe.c
index ee6d596100..462c529f19 100644
--- a/chardev/char-fe.c
+++ b/chardev/char-fe.c
@@ -356,7 +356,7 @@ guint qemu_chr_fe_add_watch(CharBackend *be, GIOCondition
cond,
}
g_source_set_callback(src, (GSourceFunc)func, user_data, NULL);
- tag = g_source_attach(src, NULL);
+ tag = g_source_attach(src, be->chr->gcontext);
g_source_unref(src);
return tag;
Otherwise it'll be still be run in main thread always.
(I guess I haven't yet encountered an EAGAIN for it so far)
>
> I suggest draining the monitor while the IOThread is still running
> (that way the AioContext and GMainContext are still operational). You
> can:
> 1. Suspend the monitor so new commands will not be read.
> 2. Wait until all responses and outbuf are empty.
>
> Another option is moving the chardev back to the main loop but I'm not
> sure if the chardev subsystem supports that.
Your suggestion is good to me. I'll do that in IOThread before it
stops. Thanks!
--
Peter Xu
