Re: [Qemu-devel] Patch 9894dc0cdcc broke something

[Daniel P . Berrangé]

On Thu, Feb 22, 2018 at 02:38:04PM +0300, Aleksey Kuleshov wrote:
> Hello!
> 
> I hit unexpected disconnections because of this patch:
> 
> commit 9894dc0cdcc397ee5b26370bc53da6d360a363c2
> Author: Daniel P. Berrange <address@hidden>
> Date:   Tue Jan 19 11:14:29 2016 +0000
> 
>     char: convert from GIOChannel to QIOChannel
>     
>     In preparation for introducing TLS support to the TCP chardev
>     backend, convert existing chardev code from using GIOChannel
>     to QIOChannel. This simplifies the chardev code by removing
>     most of the OS platform conditional code for dealing with
>     file descriptor passing.
>     
>     Signed-off-by: Daniel P. Berrange <address@hidden>
>     Message-Id: <address@hidden>
>     Signed-off-by: Paolo Bonzini <address@hidden>
> 
> breaks tcp_chr_read:
> 
> -static gboolean tcp_chr_read(GIOChannel *chan, GIOCondition cond, void 
> *opaque)
> +static gboolean tcp_chr_read(QIOChannel *chan, GIOCondition cond, void 
> *opaque)
>  {
>      CharDriverState *chr = opaque;
>      TCPCharDriver *s = chr->opaque;
> @@ -2938,9 +2801,7 @@ static gboolean tcp_chr_read(GIOChannel *chan, 
> GIOCondition cond, void *opaque)
>      if (len > s->max_size)
>          len = s->max_size;
>      size = tcp_chr_recv(chr, (void *)buf, len);
> -    if (size == 0 ||
> -        (size < 0 &&
> -         socket_error() != EAGAIN && socket_error() != EWOULDBLOCK)) {
> +    if (size == 0 || size == -1) {
>          /* connection closed */
>          tcp_chr_disconnect(chr);
>      } else if (size > 0) {
> 
> since tcp_chr_recv returns -1 on blocking:

Actually it did not do that in this patch - tcp_chr_recv returns -2
on blocking when that patch was written.

> 
> static ssize_t tcp_chr_recv(Chardev *chr, char *buf, size_t len)
> {
> ...
>     if (ret == QIO_CHANNEL_ERR_BLOCK) {
>         errno = EAGAIN;
>         ret = -1;
>     } else if (ret == -1) {
>         errno = EIO;
>     }

This was caused by by a later change

  commit b6572b4f97a7b126c7b24e165893ed9fe3d72e1f
  Author: Marc-André Lureau <address@hidden>
  Date:   Fri Mar 11 18:55:24 2016 +0100

    char: translate from QIOChannel error to errno
    

Regards,
Daniel
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