On 2012-10-08 17:18, Paolo Bonzini wrote:
> Il 08/10/2012 08:52, Jan Kiszka ha scritto:
>> On 2012-10-06 04:13, Peter Maydell wrote:
>>> On 5 October 2012 19:01, Jan Kiszka <jan.kis...@siemens.com> wrote:
>>>> I'm not a fan of this either, but the alternatives are way more
>>>> complicated. We either need to rewrite the chardev subsystem,
>>>> specifically how mux'ed devices are registered and how the active one is
>>>> selected. Or we need to avoid flushing "unrelated" BHs for block
>>>> devices. Not sure of those read requests can be postponed.
>>>
>>> Is this a regression? If it is then the obvious answer is to back
>>> out whatever broke it...
>>
>> I'm using this machine for the first time, so I cannot answer this from
>> the top of my head. However, I don't think it can be a regression.
>>
>> Mux chardevs work like this: You create the backend, then you register
>> the frontend with them, one by one. The last one registered is the first
>> one active. It should also receive the open event of chardev. But as
>> that open even is issued via a BH and last frontend, the serial device,
>> arrives after the first BH flushing, things break.
>
> Does something like this work instead?
>
> diff --git a/qemu-char.c b/qemu-char.c
> index b082bae..1ed6d49 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -465,6 +465,9 @@ static void
> mux_chr_update_read_handler(CharDriverState *chr)
> d->focus = d->mux_cnt;
> d->mux_cnt++;
> mux_chr_send_event(d, d->focus, CHR_EVENT_MUX_IN);
> + if (chr->opened) {
> + mux_chr_send_event(d, d->focus, CHR_EVENT_OPENED);
> + }
It's not (only) about a missing event for the serial frontend, it's also
about a spurious open event to the monitor. That generates unwanted
output during startup.
Jan
--
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux
