* [Qemu-devel] [PATCH] hw/char/serial: retry write if EAGAIN
@ 2018-07-16 11:07 Marc-André Lureau
2018-07-16 14:10 ` Paolo Bonzini
0 siblings, 1 reply; 2+ messages in thread
From: Marc-André Lureau @ 2018-07-16 11:07 UTC (permalink / raw)
To: qemu-devel; +Cc: pbonzini, Marc-André Lureau
If the chardev returns -1 with EAGAIN errno on write(), it should try
to send it again (EINTR is handled by the chardev itself).
This fixes commit 019288bf137183bf3407c9824655b753bfafc99f
"hw/char/serial: Only retry if qemu_chr_fe_write returns 0"
Tested-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
hw/char/serial.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)
diff --git a/hw/char/serial.c b/hw/char/serial.c
index cd7d747c68..8bd1da2fa3 100644
--- a/hw/char/serial.c
+++ b/hw/char/serial.c
@@ -261,15 +261,20 @@ static void serial_xmit(SerialState *s)
if (s->mcr & UART_MCR_LOOP) {
/* in loopback mode, say that we just received a char */
serial_receive1(s, &s->tsr, 1);
- } else if (qemu_chr_fe_write(&s->chr, &s->tsr, 1) == 0 &&
- s->tsr_retry < MAX_XMIT_RETRY) {
- assert(s->watch_tag == 0);
- s->watch_tag =
- qemu_chr_fe_add_watch(&s->chr, G_IO_OUT | G_IO_HUP,
- serial_watch_cb, s);
- if (s->watch_tag > 0) {
- s->tsr_retry++;
- return;
+ } else {
+ int rc = qemu_chr_fe_write(&s->chr, &s->tsr, 1);
+
+ if ((rc == 0 ||
+ (rc == -1 && errno == EAGAIN)) &&
+ s->tsr_retry < MAX_XMIT_RETRY) {
+ assert(s->watch_tag == 0);
+ s->watch_tag =
+ qemu_chr_fe_add_watch(&s->chr, G_IO_OUT | G_IO_HUP,
+ serial_watch_cb, s);
+ if (s->watch_tag > 0) {
+ s->tsr_retry++;
+ return;
+ }
}
}
s->tsr_retry = 0;
--
2.18.0.129.ge3331758f1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [Qemu-devel] [PATCH] hw/char/serial: retry write if EAGAIN
2018-07-16 11:07 [Qemu-devel] [PATCH] hw/char/serial: retry write if EAGAIN Marc-André Lureau
@ 2018-07-16 14:10 ` Paolo Bonzini
0 siblings, 0 replies; 2+ messages in thread
From: Paolo Bonzini @ 2018-07-16 14:10 UTC (permalink / raw)
To: Marc-André Lureau, qemu-devel
On 16/07/2018 13:07, Marc-André Lureau wrote:
> If the chardev returns -1 with EAGAIN errno on write(), it should try
> to send it again (EINTR is handled by the chardev itself).
>
> This fixes commit 019288bf137183bf3407c9824655b753bfafc99f
> "hw/char/serial: Only retry if qemu_chr_fe_write returns 0"
>
> Tested-by: Igor Mammedov <imammedo@redhat.com>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
> hw/char/serial.c | 23 ++++++++++++++---------
> 1 file changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/hw/char/serial.c b/hw/char/serial.c
> index cd7d747c68..8bd1da2fa3 100644
> --- a/hw/char/serial.c
> +++ b/hw/char/serial.c
> @@ -261,15 +261,20 @@ static void serial_xmit(SerialState *s)
> if (s->mcr & UART_MCR_LOOP) {
> /* in loopback mode, say that we just received a char */
> serial_receive1(s, &s->tsr, 1);
> - } else if (qemu_chr_fe_write(&s->chr, &s->tsr, 1) == 0 &&
> - s->tsr_retry < MAX_XMIT_RETRY) {
> - assert(s->watch_tag == 0);
> - s->watch_tag =
> - qemu_chr_fe_add_watch(&s->chr, G_IO_OUT | G_IO_HUP,
> - serial_watch_cb, s);
> - if (s->watch_tag > 0) {
> - s->tsr_retry++;
> - return;
> + } else {
> + int rc = qemu_chr_fe_write(&s->chr, &s->tsr, 1);
> +
> + if ((rc == 0 ||
> + (rc == -1 && errno == EAGAIN)) &&
> + s->tsr_retry < MAX_XMIT_RETRY) {
> + assert(s->watch_tag == 0);
> + s->watch_tag =
> + qemu_chr_fe_add_watch(&s->chr, G_IO_OUT | G_IO_HUP,
> + serial_watch_cb, s);
> + if (s->watch_tag > 0) {
> + s->tsr_retry++;
> + return;
> + }
> }
> }
> s->tsr_retry = 0;
>
Queued, thanks.
Paolo
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