[BUG] hvc_console WARN() on current upstream

[Alan Cox]

> > Seems that we are in interrupt, doing hvc_poll, which does
> > tty_flip_buffer_push

Which means that someone has tty->low_latency set and is calling
tty_flip_buffer_push in an IRQ. That has never been allowed or safe, and
now it hurts ;)

/**
 *      tty_flip_buffer_push    -       terminal
 *      @tty: tty to push
 * 
 *      Queue a push of the terminal flip buffers to the line discipline.
This
 *      function must not be called from IRQ context if tty->low_latency
is set *
 *      In the event of the queue being busy for flipping the work will be
 *      held off and retried later.
 *
 *      Locking: tty buffer lock. Driver locks in low latency mode.
 */


That comment has been there for some years in varying formats