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

[Marc-André Lureau]

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
$ ./scripts/qmp/qmp-shell -v -p /tmp/qmp.sock
Welcome to the QMP low-level shell!
Connected to QEMU 5.2.0

(QEMU) screendump filename=/tmp/foo
{
    "arguments": {
        "filename": "/tmp/foo"
    },
    "execute": "screendump"
}
{
    "return": {}
}

etc.. multiple times at different stages.

Can you also provide a backtrace?




-- 
Marc-André Lureau