Re: [Qemu-devel] [PATCH v2] qemu-char: Do not disconnect when there's data for reading

[Markus Armbruster]

Zifei Tong <address@hidden> writes:

> Hi Markus,
>
> On Thu, Sep 18, 2014 at 8:11 PM, Markus Armbruster <address@hidden> wrote:
>> Zifei Tong <address@hidden> writes:
>>
>>> After commit 812c1057f6175ac9a9829fa2920a2b5783814193 (Handle G_IO_HUP
>>> in tcp_chr_read for tcp chardev), connections are disconnected when in
>>> G_IO_HUP condition.
>>>
>>> However, it's possible that there is still data for reading in the channel.
>>> In that case, the remaining data is not handled.
>>>
>>> I saw a related bug when running socat in write-only mode, after
>>>
>>>   $ echo "quit" | socat -u - UNIX-CONNECT:qemu-monitor
>>>
>>> the monitor won't not run the 'quit' command.
>>>
>>> Instead of GIOCondition, this patch uses the return value of tcp_chr_recv()
>>> to check the state of connection as suggested by Kirill.
[...]
>>> @@ -2705,7 +2699,7 @@ 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) {
>>> +    if (size == 0 || (size < 0 && !(errno == EAGAIN || errno == EINTR))) {
>>>          /* connection closed */
>>>          tcp_chr_disconnect(chr);
>>>      } else if (size > 0) {
>>
>> What about EWOULDBLOCK?
>
> I thought EAGAIN and EWOULDBLOCK was the same thing, until Google told
> me it's not the case on some platforms like HP-UX, AIX and Tru64.
>
> Shall we add one more check to support these old platforms?

Yes, please!

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