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.
(However I might be completely missing the data that didn't get written
as a result of that partial write, so the output gets corrupted. I
guess I still need to handle partial writes for that.)
Amit
