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Re: [Qemu-devel] [PATCH] serial: poll the serial console with G_IO_HUP
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH] serial: poll the serial console with G_IO_HUP |
Date: |
Mon, 28 Apr 2014 11:19:20 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 |
Il 22/04/2014 19:08, Roger Pau Monne ha scritto:
> On FreeBSD polling a master pty while the other end is not connected
> with G_IO_OUT only results in an endless wait. This is different from
> the Linux behaviour, that returns immediately. In order to demonstrate
> this, I have the following example code:
>
> http://xenbits.xen.org/people/royger/test_poll.c
>
> When executed on Linux:
>
> $ ./test_poll
> In callback
>
> On FreeBSD instead, the callback never gets called:
>
> $ ./test_poll
>
> So, in order to workaround this, poll the source with G_IO_HUP (which
> makes the code behave the same way on both Linux and FreeBSD).
>
> Signed-off-by: Roger Pau Monné <address@hidden>
> Cc: Peter Crosthwaite <address@hidden>
> Cc: Michael Tokarev <address@hidden>
> Cc: "Andreas Färber" <address@hidden>
> Cc: Paolo Bonzini <address@hidden>
> Cc: address@hidden
> ---
> hw/char/serial.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/hw/char/serial.c b/hw/char/serial.c
> index 6025592..ab9c40f 100644
> --- a/hw/char/serial.c
> +++ b/hw/char/serial.c
> @@ -243,7 +243,7 @@ static gboolean serial_xmit(GIOChannel *chan,
> GIOCondition cond, void *opaque)
> serial_receive1(s, &s->tsr, 1);
> } else if (qemu_chr_fe_write(s->chr, &s->tsr, 1) != 1) {
> if (s->tsr_retry >= 0 && s->tsr_retry < MAX_XMIT_RETRY &&
> - qemu_chr_fe_add_watch(s->chr, G_IO_OUT, serial_xmit, s) > 0) {
> + qemu_chr_fe_add_watch(s->chr, G_IO_OUT|G_IO_HUP, serial_xmit, s)
> > 0) {
> s->tsr_retry++;
> return FALSE;
> }
>
The patch looks good. However, the same problem is most likely there
in other places:
hw/char/cadence_uart.c: int r = qemu_chr_fe_add_watch(s->chr, G_IO_OUT,
cadence_uart_xmit, s);
hw/char/serial.c: qemu_chr_fe_add_watch(s->chr, G_IO_OUT,
serial_xmit, s) > 0) {
hw/char/virtio-console.c: vcon->watch =
qemu_chr_fe_add_watch(vcon->chr, G_IO_OUT,
hw/usb/redirect.c: dev->watch = qemu_chr_fe_add_watch(dev->cs,
G_IO_OUT,
monitor.c: mon->watch = qemu_chr_fe_add_watch(mon->chr, G_IO_OUT,
Should we add G_IO_HUP everywhere we have G_IO_OUT?
Or perhaps even in qemu_chr_fe_add_watch (I don't really like this,
but I will shoot it out...)?
Paolo