[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH] serial: poll the serial console with G_IO_HUP
From: |
Roger Pau Monné |
Subject: |
Re: [Qemu-devel] [PATCH] serial: poll the serial console with G_IO_HUP |
Date: |
Mon, 28 Apr 2014 11:32:57 +0200 |
User-agent: |
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 |
On 28/04/14 11:19, Paolo Bonzini wrote:
> 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) {
This is the one I've fixed.
> 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?
IMOH it seems better to add G_IO_HUP to those other callers rather than
appending it in qemu_chr_fe_add_watch unconditionally, but I don't have
a strong opinion. If no one else expresses an interest into having it
added to qemu_chr_fe_add_watch I will send a new version that also fixes
the other callers listed above.
Roger.