Re: [PATCH v2] serial: 8250: fix shared IRQ startup race causing IRQ warning

[Jiri Slaby]

Ah, you are fixing the same thing as:
https://lore.kernel.org/all/20260707-bug-221579-8250-shared-irq-race-v6-1-f8c499a90bdd@xxxxxxxxx/

I did not look up who of you was first.

Note the above contains you in the commit log:
Reported-by: Wang Zhaolong <wangzhaolong@xxxxxxxxx>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221579

You both CCed each other, so you know the other's submission. I don't 
understand why you both send the patch? Anyway, you guys speak to each 
other and decide who sends the (fixed) patch.

On 08. 07. 26, 5:11, Wang Zhaolong wrote:
...
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -154,10 +152,18 @@ static struct irq_info *serial_get_or_create_irq_info(const struct uart_8250_por
>   static int serial_link_irq_chain(struct uart_8250_port *up)
>   {
>   	struct irq_info *i;
>   	int ret;
>   
> +	/*
> +	 * Keep the hash lock held until the first request_irq() completes.
> +	 * The first port publishes i->head before request_irq() starts the IRQ;
> +	 * a second port sharing the IRQ must not join the chain and run the
> +	 * THRE test while the IRQ core is still bringing the line up.
> +	 */
> +	guard(mutex)(&hash_mutex);

The same as in the other patch:
hash_mutex is no longer an appropriate name for this lock.

> +
>   	i = serial_get_or_create_irq_info(up);
>   	if (IS_ERR(i))
>   		return PTR_ERR(i);
>   
>   	scoped_guard(spinlock_irq, &i->lock) {

thanks,
--
js
suse labs