Re: [PATCH] hw/char/pl011: Output characters using best-effort mode

[Gavin Shan <gshan@redhat.com>]

On 2/22/20 5:15 AM, Paolo Bonzini wrote:
> On 21/02/20 14:14, Peter Maydell wrote:
>> The initial case reported by Gavin in this thread is
>> "-serial tcp:127.0.0.1:50900" with the other end being a program which
>> listens on TCP port 50900 and then sleeps without accepting any incoming
>> connections, which blocks the serial port output and effectively blocks
>> the guest bootup. If you want to insulate the guest from badly
>> behaved consumers like that (or the related consumer who accepts
>> the connection and then just doesn't read data from it) you probably
>> need to deal with more than just POLLHUP. But I'm not sure how much
>> we should care about these cases as opposed to just telling users
>> not to do that...
> 
> No, I think we don't do anything (on purpose; that is, it was considered
> the lesser evil) for x86 in that case.
> 

Paolo and Peter, thanks for your time on the discussion. So I think the
conclusion is we don't do anything for pl011 either? :)

Actually, the issue was reported by libvirt developer. A VM is started
with serial on tcp socket, which is never accepted on server side. It
practically blocks the VM to boot up. I will tell the libvirt developer
to hack their code to avoid the race if we don't do anything in qemu.

Thanks,
Gavin