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

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Message-ID: <708697c8-8e8a-fecb-23a5-939194c3935c@linux.intel.com>
Date: Wed, 11 Jun 2025 16:25:26 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
    linux-serial <linux-serial@...r.kernel.org>, 
    LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 32/33] serial: 8250: use hashtable

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@...nel.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.