* [PATCH] serial: poll the serial console with G_IO_HUP
@ 2014-04-22 17:08 Roger Pau Monne
0 siblings, 0 replies; 3+ messages in thread
From: Roger Pau Monne @ 2014-04-22 17:08 UTC (permalink / raw)
To: qemu-devel
Cc: Peter Crosthwaite, Michael Tokarev, xen-devel, Paolo Bonzini,
Andreas Färber, Roger Pau Monne
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 <roger.pau@citrix.com>
Cc: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Cc: Michael Tokarev <mjt@tls.msk.ru>
Cc: "Andreas Färber" <afaerber@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: xen-devel@lists.xenproject.org
---
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;
}
--
1.7.7.5 (Apple Git-26)
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^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] serial: poll the serial console with G_IO_HUP
[not found] ` <535E1D18.80709@redhat.com>
@ 2014-04-28 9:32 ` Roger Pau Monné
0 siblings, 0 replies; 3+ messages in thread
From: Roger Pau Monné @ 2014-04-28 9:32 UTC (permalink / raw)
To: Paolo Bonzini, qemu-devel
Cc: xen-devel, Peter Crosthwaite, Michael Tokarev, Andreas Färber
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 <roger.pau@citrix.com>
>> Cc: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
>> Cc: Michael Tokarev <mjt@tls.msk.ru>
>> Cc: "Andreas Färber" <afaerber@suse.de>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: xen-devel@lists.xenproject.org
>> ---
>> 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.
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] serial: poll the serial console with G_IO_HUP
[not found] <1398186535-66539-1-git-send-email-roger.pau@citrix.com>
@ 2014-04-28 9:19 ` Paolo Bonzini
[not found] ` <535E1D18.80709@redhat.com>
1 sibling, 0 replies; 3+ messages in thread
From: Paolo Bonzini @ 2014-04-28 9:19 UTC (permalink / raw)
To: Roger Pau Monne, qemu-devel
Cc: xen-devel, Peter Crosthwaite, Michael Tokarev, Andreas Färber
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 <roger.pau@citrix.com>
> Cc: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
> Cc: Michael Tokarev <mjt@tls.msk.ru>
> Cc: "Andreas Färber" <afaerber@suse.de>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: xen-devel@lists.xenproject.org
> ---
> 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
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^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2014-04-28 9:33 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2014-04-22 17:08 [PATCH] serial: poll the serial console with G_IO_HUP Roger Pau Monne
[not found] <1398186535-66539-1-git-send-email-roger.pau@citrix.com>
2014-04-28 9:19 ` Paolo Bonzini
[not found] ` <535E1D18.80709@redhat.com>
2014-04-28 9:32 ` Roger Pau Monné
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