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