Re: [RFC/PATCH] virtio-console: wait for console ports

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 22/09/11 12:08, Amit Shah wrote:
>> +	/* If there was an early virtio console, assume that there are no
>> +	 * other consoles. We need to wait until the hvc_alloc matches the
>> +	 * hvc_instantiate, otherwise tty_open will complain, resulting in
>> +	 * a "Warning: unable to open an initial console" boot failure.
>> +	 * Without multiport this is done in add_port above. With multiport
>> +	 * this might take some host<->guest communication - thus we have to
>> +	 * wait. */
> 
> This file uses comments in the form
>   /*
>    * ...
>    */

Will fix.

> 
>> +	if (multiport && early)
>> +		wait_for_completion(&port_added);
>> +
> 
> Can there be a problem to not timeout this wait?  Maybe it's not a
> real problem; just thinking out aloud.

I had the same thoughts. I then asked myself, how big the timeout has to be - and
the answer was it really depends on the host load. So we can certainly use
wait_for_completion_timeout(&port_added, HZ*<x>);
which will work in 99.9% of all cases. It might still cause spurious boot failures,
if for some reasons it takes too long.
So the big question is, is there a case were virtio is used as an early console
but virtio_console does not register a console during probe. Ideas?

Christian