> On (Wed) Dec 01 2010 [11:59:35], Paul Brook wrote:
> > > > > - qemu_chr_write(vcon->chr, buf, len);
> > > > > + ret = qemu_chr_write(vcon->chr, buf, len);
> > > > > + if (ret == -EAGAIN) {
> > > > > + virtio_serial_throttle_port(port, true);
> > > > > + }
> > > > >
> > > > > }
> > > >
> > > > This looks wrong. It will loose data in the case of a partial write
> > > > (i.e. ret < len)
> > >
> > > That doesn't happen currently (qemu_chr_write doesn't return a value >
> > > 0 but < len).
> > >
> > > I had code in there to handle it, but that would change behaviour for
> > > current users of qemu_chr_write(), which is a risk.
> >
> > Doesn't that make the code almost completely pointless?
>
> Not really -- I did have code for partial writes, but removed it before
> this submission (had it in previous versions).
>
> The (new) do_send loop:
>
> len = len1;
> while (len > 0) {
> ret = write(fd, buf, len);
> if (ret < 0) {
> if (errno == EAGAIN && nonblock) {
> return -EAGAIN;
> }
> if (errno != EINTR && errno != EAGAIN) {
> return -1;
> }
> } else if (ret == 0) {
> break;
> } else {
> buf += ret;
> len -= ret;
> }
> }
>
> when there's a partial write, it tries to do a write again, which will
> fail with -EAGAIN.
Doesn't that cause the first partial chunk to be incorrectly transmitted
twice? You may only return EAGAIN if no data was transmitted.
Paul
