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Date: Sun, 3 Aug 2008 16:14:47 +0100
From: Alan Cox <alan@...rguk.ukuu.org.uk>
To: Yinghai Lu <yhlu.kernel@...il.com>
Cc: Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
Mike Travis <travis@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, Yinghai Lu <yhlu.kernel@...il.com>
Subject: Re: [PATCH 21/25] serial: change remove NR_IRQS in 8250.c v2
On Sat, 2 Aug 2008 19:59:21 -0700
Yinghai Lu <yhlu.kernel@...il.com> wrote:
> use small array with index to handle irq locking for serial port
> hope 32 slot is enough
Untested alternative approach
8250: Remove NR_IRQ usage
From: Alan Cox <alan@...hat.com>
---
drivers/serial/68328serial.c | 11 ++---------
drivers/serial/8250.c | 41 ++++++++++++++++++++++++++++++++++-------
2 files changed, 36 insertions(+), 16 deletions(-)
diff --git a/drivers/serial/68328serial.c b/drivers/serial/68328serial.c
index 381b12a..277b78d 100644
--- a/drivers/serial/68328serial.c
+++ b/drivers/serial/68328serial.c
@@ -66,7 +66,6 @@
#endif
static struct m68k_serial m68k_soft[NR_PORTS];
-struct m68k_serial *IRQ_ports[NR_IRQS];
static unsigned int uart_irqs[NR_PORTS] = UART_IRQ_DEFNS;
@@ -375,15 +374,11 @@ clear_and_return:
*/
irqreturn_t rs_interrupt(int irq, void *dev_id)
{
- struct m68k_serial * info;
+ struct m68k_serial * info = dev_id;
m68328_uart *uart;
unsigned short rx;
unsigned short tx;
- info = IRQ_ports[irq];
- if(!info)
- return IRQ_NONE;
-
uart = &uart_addr[info->line];
rx = uart->urx.w;
@@ -1383,8 +1378,6 @@ rs68328_init(void)
info->port, info->irq);
printk(" is a builtin MC68328 UART\n");
- IRQ_ports[info->irq] = info; /* waste of space */
-
#ifdef CONFIG_M68VZ328
if (i > 0 )
PJSEL &= 0xCF; /* PSW enable second port output */
@@ -1393,7 +1386,7 @@ rs68328_init(void)
if (request_irq(uart_irqs[i],
rs_interrupt,
IRQF_DISABLED,
- "M68328_UART", NULL))
+ "M68328_UART", info))
panic("Unable to attach 68328 serial interrupt\n");
}
local_irq_restore(flags);
diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index a97f1ae..7165e88 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -145,11 +145,14 @@ struct uart_8250_port {
};
struct irq_info {
- spinlock_t lock;
+ struct irq_info *next;
+ int irq;
+ spinlock_t lock; /* Protects list not the hash */
struct list_head *head;
};
-static struct irq_info irq_lists[NR_IRQS];
+static struct irq_info *irq_lists[NR_IRQ_HASH];
+static DEFINE_SPINLOCK(hash_lock); /* Used to walk the hash */
/*
* Here we define the default xmit fifo size used for each type of UART.
@@ -1541,9 +1544,28 @@ static void serial_do_unlink(struct irq_info *i, struct uart_8250_port *up)
static int serial_link_irq_chain(struct uart_8250_port *up)
{
- struct irq_info *i = irq_lists + up->port.irq;
+ struct irq_info **list, *i;
int ret, irq_flags = up->port.flags & UPF_SHARE_IRQ ? IRQF_SHARED : 0;
+ spin_lock(&hash_lock);
+
+ list = &irq_lists[up->port.irq % NR_IRQ_HASH];
+ i = * list;
+
+ while(i != NULL && i->irq != up->port.irq)
+ i = i->next;
+ if (i == NULL) {
+ i = kzalloc(sizeof(struct irq_info), GFP_KERNEL);
+ if (i == NULL) {
+ spin_unlock(&hash_lock);
+ return -ENOMEM;
+ }
+ spin_lock_init(&i->lock);
+ i->next = *list;
+ *list = i;
+ }
+ spin_unlock(&hash_lock);
+
spin_lock_irq(&i->lock);
if (i->head) {
@@ -1567,8 +1589,16 @@ 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 = irq_lists + up->port.irq;
+ struct irq_info *i;
+
+ spin_lock(&hash_lock);
+ i = irq_lists[up->port.irq % NR_IRQ_HASH];
+ while(i != NULL && i->irq != up->port.irq)
+ i = i->next;
+ spin_unlock(&hash_lock);
+
+ BUG_ON(i == NULL);
BUG_ON(i->head == NULL);
if (list_empty(i->head))
@@ -2951,9 +2981,6 @@ static int __init serial8250_init(void)
"%d ports, IRQ sharing %sabled\n", nr_uarts,
share_irqs ? "en" : "dis");
- for (i = 0; i < NR_IRQS; i++)
- spin_lock_init(&irq_lists[i].lock);
-
ret = uart_register_driver(&serial8250_reg);
if (ret)
goto out;
--
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