Re: [PATCH v2] virtio: console: fix lost wakeup when device is written and polled

["Arnd Bergmann" <arnd@arndb.de>]

On Mon, Dec 22, 2025, at 17:04, Lorenz Bauer wrote:
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -971,10 +971,17 @@ static __poll_t port_fops_poll(struct file *filp, 
> poll_table *wait)
>  		return EPOLLHUP;
>  	}
>  	ret = 0;
> -	if (!will_read_block(port))
> +
> +	spin_lock(&port->inbuf_lock);
> +	if (port->inbuf)

As far as I can tell, you got the interrupt flag handling wrong
in both places: port_fops_poll() is called with interrupts
enabled, so you have to use spin_lock_irq() to block the
interrupt from hanging.

> @@ -1705,6 +1713,10 @@ static void out_intr(struct virtqueue *vq)
>  		return;
>  	}
> 
> +	spin_lock_irqsave(&port->outvq_lock, flags);
> +	reclaim_consumed_buffers(port);
> +	spin_unlock_irqrestore(&port->outvq_lock, flags);
> +
>  	wake_up_interruptible(&port->waitqueue);

The callback seems to always be called with interrupts
disabled(), so here it's safe to use spin_lock() instead
of spin_lock_irqsave().

     Arnd