Re: [PATCH v2 3/3] console: make QMP/HMP screendump run in coroutine

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Gerd Hoffmann (kraxel@redhat.com) wrote:
> On Wed, Jan 20, 2021 at 06:29:41PM +0400, Marc-André Lureau wrote:
> > Hi Gerd
> > 
> > On Wed, Jan 20, 2021 at 6:18 PM Gerd Hoffmann <kraxel@redhat.com> wrote:
> > >
> > > On Tue, Oct 27, 2020 at 05:36:02PM +0400, marcandre.lureau@redhat.com wrote:
> > > > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> > > >
> > > > Thanks to the monitors' coroutine support (merge commit b7092cda1b3),
> > > > the screendump handler can trigger a graphic_hw_update(), yield and let
> > > > the main loop run until update is done. Then the handler is resumed, and
> > > > ppm_save() will write the screen image to disk in the coroutine context.
> > > >
> > > > The IO is still blocking though, as the file is set blocking so far,
> > > > this could be addressed by some future change (with other caveats).
> > > >
> > > > Related to:
> > > > https://bugzilla.redhat.com/show_bug.cgi?id=1230527
> > > >
> > > > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > > > Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
> > >
> > > Hmm, just noticed that with this patch applied screendump hangs for vms
> > > with "-device qxl" ("-device qxl-vga" works fine).
> > >
> > > Can you have a look?
> > 
> > Weird, I cannot reproduce. I tried this way:
> > 
> > $ qemu-system-x86_64 -m 4096 -enable-kvm -device qxl -qmp
> > unix:/tmp/qmp.sock,server -snapshot rhel8
> 
> -vga none or -nodefaults is needed, otherwise you'll get both VGA and
> qxl devices.
> 
> Using gtk ui, just saying "screendump /tmp/x" in the monitor tab.
> 
> > Can you also provide a backtrace?
> 

> Thread 1 (Thread 0x7fab988e4440 (LWP 2822797) "qemu-system-x86"):
> #0  0x00007fab9c8a990e in ppoll () at /lib64/libc.so.6
> #1  0x000055f3f9c33dd5 in fdmon_poll_wait ()
> #2  0x000055f3f9c26c6a in aio_poll ()

> #3  0x000055f3f99552a5 in handle_hmp_command ()

That's the :

1117	        AIO_WAIT_WHILE(qemu_get_aio_context(), !data.done);

Dave

> #4  0x000055f3f99553cd in monitor_command_cb ()
> #5  0x000055f3f9c29a37 in readline_handle_byte ()
> #6  0x000055f3f995541b in monitor_read ()
> #7  0x000055f3f992373c in gd_vc_in ()
> #8  0x00007fab9d84e22d in _vte_marshal_VOID__STRING_UINTv () at /lib64/libvte-2.91.so.0
> #9  0x00007fab9d8e9080 in g_signal_emit_valist () at /lib64/libgobject-2.0.so.0
> #10 0x00007fab9d8e91a3 in g_signal_emit () at /lib64/libgobject-2.0.so.0
> #11 0x00007fab9d858a7e in vte::terminal::Terminal::emit_commit(std::basic_string_view<char, std::char_traits<char> > const&) () at /lib64/libvte-2.91.so.0
> #12 0x00007fab9d85cf1d in vte::terminal::Terminal::send_child(std::basic_string_view<char, std::char_traits<char> > const&) () at /lib64/libvte-2.91.so.0
> #13 0x00007fab9d8715bc in vte_terminal_key_press(_GtkWidget*, _GdkEventKey*) () at /lib64/libvte-2.91.so.0
> #14 0x00007fab9d47eccc in _gtk_marshal_BOOLEAN__BOXEDv () at /lib64/libgtk-3.so.0
> #15 0x00007fab9d8e869a in g_signal_emit_valist () at /lib64/libgobject-2.0.so.0
> #16 0x00007fab9d8e91a3 in g_signal_emit () at /lib64/libgobject-2.0.so.0
> #17 0x00007fab9d441bb4 in gtk_widget_event_internal.part.0.lto_priv () at /lib64/libgtk-3.so.0
> #18 0x00007fab9d45029b in gtk_window_propagate_key_event () at /lib64/libgtk-3.so.0
> #19 0x00007fab9d453283 in gtk_window_key_press_event.lto_priv () at /lib64/libgtk-3.so.0
> #20 0x00007fab9d47eccc in _gtk_marshal_BOOLEAN__BOXEDv () at /lib64/libgtk-3.so.0
> #21 0x00007fab9d8e9080 in g_signal_emit_valist () at /lib64/libgobject-2.0.so.0
> #22 0x00007fab9d8e91a3 in g_signal_emit () at /lib64/libgobject-2.0.so.0
> #23 0x00007fab9d441bb4 in gtk_widget_event_internal.part.0.lto_priv () at /lib64/libgtk-3.so.0
> #24 0x00007fab9d2e000f in propagate_event.lto_priv () at /lib64/libgtk-3.so.0
> #25 0x00007fab9d2e1223 in gtk_main_do_event () at /lib64/libgtk-3.so.0
> #26 0x00007fab9cfbb633 in _gdk_event_emit () at /lib64/libgdk-3.so.0
> #27 0x00007fab9d022ba6 in gdk_event_source_dispatch.lto_priv () at /lib64/libgdk-3.so.0
> #28 0x00007fab9db3296f in g_main_context_dispatch () at /lib64/libglib-2.0.so.0
> #29 0x000055f3f9c24f58 in main_loop_wait ()
> #30 0x000055f3f9a564b1 in qemu_main_loop ()
> #31 0x000055f3f97609ee in main ()
> 
> take care,
>   Gerd
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK