On 21/06/2017 15:23, Gerd Hoffmann wrote:
> Drop the temporary workaround for the broken display updates.
> All display adapters are updated, so this should be safe without
> causing regressions.
It seems it breaks QMP command 'migrate "exec:cat>mig"'.
The command hangs and doesn't create the file.
It happens with qemu-system-ppc64 on x86 (so TCG mode).
my command:
./ppc64-softmmu/qemu-system-ppc64 -serial mon:stdio
I wait SLOF fails to find an OS, and:
Ctrl-a c
(qemu) migrate -d "exec:cat>mig"
The file is not created and the command hangs:
#0 in __lll_lock_wait
#1 in pthread_mutex_lock
#2 in qemu_mutex_lock
#3 in rcu_init_lock
#4 in fork
#5 in qemu_fork
#6 in qio_channel_command_new_spawn
#7 in exec_start_outgoing_migration
#8 in qmp_migrate
...
It looks like a deadlock.
Laurent
> Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
> Acked-by: Alex Bennée <alex.ben...@linaro.org>
> Message-id: 20170614084538.32480-1-kra...@redhat.com
> ---
> ui/console.c | 25 +------------------------
> 1 file changed, 1 insertion(+), 24 deletions(-)
>
> diff --git a/ui/console.c b/ui/console.c
> index d914cced53..af0c56c600 100644
> --- a/ui/console.c
> +++ b/ui/console.c
> @@ -1579,36 +1579,13 @@ bool dpy_gfx_check_format(QemuConsole *con,
> return true;
> }
>
> -/*
> - * Safe DPY refresh for TCG guests. We use the exclusive mechanism to
> - * ensure the TCG vCPUs are quiescent so we can avoid races between
> - * dirty page tracking for direct frame-buffer access by the guest.
> - *
> - * This is a temporary stopgap until we've fixed the dirty tracking
> - * races in display adapters.
> - */
> -static void do_safe_dpy_refresh(DisplayChangeListener *dcl)
> -{
> - qemu_mutex_unlock_iothread();
> - start_exclusive();
> - qemu_mutex_lock_iothread();
> - dcl->ops->dpy_refresh(dcl);
> - qemu_mutex_unlock_iothread();
> - end_exclusive();
> - qemu_mutex_lock_iothread();
> -}
> -
> static void dpy_refresh(DisplayState *s)
> {
> DisplayChangeListener *dcl;
>
> QLIST_FOREACH(dcl, &s->listeners, next) {
> if (dcl->ops->dpy_refresh) {
> - if (tcg_enabled()) {
> - do_safe_dpy_refresh(dcl);
> - } else {
> - dcl->ops->dpy_refresh(dcl);
> - }
> + dcl->ops->dpy_refresh(dcl);
> }
> }
> }
>
