Re: [PATCH 32/33] serial: 8250: use hashtable

Ilpo Järvinen
2025-06-11T13:25:34Z

On Wed, 11 Jun 2025, Jiri Slaby (SUSE) wrote:

> Instead of open-coding the hash table, use the one provided by
> hashtable.h. The semantics is the same, except the code needs not to
> compute the hash bucket on its own.
>
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
> ---
> drivers/tty/serial/8250/8250_core.c | 24 ++++++++----------------
> 1 file changed, 8 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
> index 10f25bae9f46..a6ecb8575da4 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -13,6 +13,7 @@
> */
>
> #include <linux/acpi.h>
> +#include <linux/hashtable.h>
> #include <linux/module.h>
> #include <linux/moduleparam.h>
> #include <linux/ioport.h>
> @@ -47,8 +48,8 @@ struct irq_info {
> struct list_head *head;
> };
>
> -#define NR_IRQ_HASH 32 /* Can be adjusted later */
> -static struct hlist_head irq_lists[NR_IRQ_HASH];
> +#define IRQ_HASH_BITS 5 /* Can be adjusted later */
> +static DEFINE_HASHTABLE(irq_lists, IRQ_HASH_BITS);
> static DEFINE_MUTEX(hash_mutex); /* Used to walk the hash */
>
> /*
> @@ -75,11 +76,8 @@ static irqreturn_t serial8250_interrupt(int irq, void *dev_id)
>
> l = i->head;
> do {
> - struct uart_8250_port *up;
> - struct uart_port *port;
> -
> - up = list_entry(l, struct uart_8250_port, list);
> - port = &up->port;
> + struct uart_8250_port *up = list_entry(l, struct uart_8250_port, list);
> + struct uart_port *port = &up->port;

Isn't this entirely unrelated change/cleanup?

>
> if (port->handle_irq(port)) {
> handled = 1;
> @@ -132,14 +130,11 @@ static void serial_do_unlink(struct irq_info *i, struct uart_8250_port *up)
> */
> static struct irq_info *serial_get_or_create_irq_info(const struct uart_8250_port *up)
> {
> - struct hlist_head *h;
> struct irq_info *i;
>
> mutex_lock(&hash_mutex);
>
> - h = &irq_lists[up->port.irq % NR_IRQ_HASH];
> -
> - hlist_for_each_entry(i, h, node)
> + hash_for_each_possible(irq_lists, i, node, up->port.irq)
> if (i->irq == up->port.irq)
> goto unlock;
>
> @@ -150,7 +145,7 @@ static struct irq_info *serial_get_or_create_irq_info(const struct uart_8250_por
> }
> spin_lock_init(&i->lock);
> i->irq = up->port.irq;
> - hlist_add_head(&i->node, h);
> + hash_add(irq_lists, &i->node, i->irq);
> unlock:
> mutex_unlock(&hash_mutex);
>
> @@ -189,13 +184,10 @@ static int serial_link_irq_chain(struct uart_8250_port *up)
> static void serial_unlink_irq_chain(struct uart_8250_port *up)
> {
> struct irq_info *i;
> - struct hlist_head *h;
>
> mutex_lock(&hash_mutex);
>
> - h = &irq_lists[up->port.irq % NR_IRQ_HASH];
> -
> - hlist_for_each_entry(i, h, node)
> + hash_for_each_possible(irq_lists, i, node, up->port.irq)
> if (i->irq == up->port.irq)
> break;
>
>

--
i.