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hvc_console: rework setup to replace irq functions with callbacks

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This patch tries to change hvc_console to not use request_irq/free_irq if
the backend does not use irqs. This allows virtio_console to use hvc_console
without having a linker reference to request_irq/free_irq.

In addition, together with patch 2/3 it improves the performance for virtio
console input. (an earlier version of this patch was tested by Yajin on lguest)

The irq specific code is moved to hvc_irq.c and selected by the drivers that
use irqs (System p, System i, XEN).

I replaced "int irq" with the opaque "int data". The request_irq and
free_irq calls are replaced with notifier_add and notifier_del. I have also
changed the code a bit to call the notifier_add and notifier_del inside the
spinlock area as the callbacks are found via hp->ops.

Changes since last version:
o remove ifdef
o reintroduce "irq_requested" as "notified"
o cleanups, sparse..

I did not move the timer based polling into a separate polling scheme. I
played with several variants, but it seems we need to sleep/schedule in
a thread even for irq based consoles, as there are throttleing and buffer
size constraints.

I also kept hvc_struct defined in hvc_console.h so that hvc_irq.c can access
the irq_requested element.

Feedback is appreciated. virtio_console is currently the only available console
for kvm on s390. I plan to push this change as soon as all affected parties
agree on it. I would love to get test results from System p, Xen etc.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Christian Borntraeger
2008-06-20 15:24:08 +02:00
committed by Rusty Russell
parent 066f4d82a6
commit 611e097d77
8 changed files with 105 additions and 67 deletions
Download Patch File Download Diff File Expand all files Collapse all files

81
drivers/char/hvc_console.c
View File

@ -27,7 +27,6 @@
#include <linux/init.h>
#include <linux/kbd_kern.h>
#include <linux/kernel.h>
#include <linux/kref.h>
#include <linux/kthread.h>
#include <linux/list.h>
#include <linux/module.h>
@ -75,23 +74,6 @@ static int hvc_init(void);
static int sysrq_pressed;
#endif
struct hvc_struct {
spinlock_t lock;
int index;
struct tty_struct *tty;
unsigned int count;
int do_wakeup;
char *outbuf;
int outbuf_size;
int n_outbuf;
uint32_t vtermno;
struct hv_ops *ops;
int irq_requested;
int irq;
struct list_head next;
struct kref kref; /* ref count & hvc_struct lifetime */
};
/* dynamic list of hvc_struct instances */
static LIST_HEAD(hvc_structs);
@ -300,26 +282,12 @@ int hvc_instantiate(uint32_t vtermno, int index, struct hv_ops *ops)
}
/* Wake the sleeping khvcd */
static void hvc_kick(void)
void hvc_kick(void)
{
hvc_kicked = 1;
wake_up_process(hvc_task);
}
static int hvc_poll(struct hvc_struct *hp);
/*
* NOTE: This API isn't used if the console adapter doesn't support interrupts.
* In this case the console is poll driven.
*/
static irqreturn_t hvc_handle_interrupt(int irq, void *dev_instance)
{
/* if hvc_poll request a repoll, then kick the hvcd thread */
if (hvc_poll(dev_instance))
hvc_kick();
return IRQ_HANDLED;
}
static void hvc_unthrottle(struct tty_struct *tty)
{
hvc_kick();
@ -333,7 +301,6 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
{
struct hvc_struct *hp;
unsigned long flags;
int irq = 0;
int rc = 0;
/* Auto increments kref reference if found. */
@ -352,18 +319,15 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
tty->low_latency = 1; /* Makes flushes to ldisc synchronous. */
hp->tty = tty;
/* Save for request_irq outside of spin_lock. */
irq = hp->irq;
if (irq)
hp->irq_requested = 1;
if (hp->ops->notifier_add)
rc = hp->ops->notifier_add(hp, hp->data);
spin_unlock_irqrestore(&hp->lock, flags);
/* check error, fallback to non-irq */
if (irq)
rc = request_irq(irq, hvc_handle_interrupt, IRQF_DISABLED, "hvc_console", hp);
/*
* If the request_irq() fails and we return an error. The tty layer
* If the notifier fails we return an error. The tty layer
* will call hvc_close() after a failed open but we don't want to clean
* up there so we'll clean up here and clear out the previously set
* tty fields and return the kref reference.
@ -371,7 +335,6 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
if (rc) {
spin_lock_irqsave(&hp->lock, flags);
hp->tty = NULL;
hp->irq_requested = 0;
spin_unlock_irqrestore(&hp->lock, flags);
tty->driver_data = NULL;
kref_put(&hp->kref, destroy_hvc_struct);
@ -386,7 +349,6 @@ static int hvc_open(struct tty_struct *tty, struct file * filp)
static void hvc_close(struct tty_struct *tty, struct file * filp)
{
struct hvc_struct *hp;
int irq = 0;
unsigned long flags;
if (tty_hung_up_p(filp))
@ -404,9 +366,8 @@ static void hvc_close(struct tty_struct *tty, struct file * filp)
spin_lock_irqsave(&hp->lock, flags);
if (--hp->count == 0) {
if (hp->irq_requested)
irq = hp->irq;
hp->irq_requested = 0;
if (hp->ops->notifier_del)
hp->ops->notifier_del(hp, hp->data);
/* We are done with the tty pointer now. */
hp->tty = NULL;
@ -418,10 +379,6 @@ static void hvc_close(struct tty_struct *tty, struct file * filp)
* waking periodically to check chars_in_buffer().
*/
tty_wait_until_sent(tty, HVC_CLOSE_WAIT);
if (irq)
free_irq(irq, hp);
} else {
if (hp->count < 0)
printk(KERN_ERR "hvc_close %X: oops, count is %d\n",
@ -436,7 +393,6 @@ static void hvc_hangup(struct tty_struct *tty)
{
struct hvc_struct *hp = tty->driver_data;
unsigned long flags;
int irq = 0;
int temp_open_count;
if (!hp)
@ -458,13 +414,12 @@ static void hvc_hangup(struct tty_struct *tty)
hp->count = 0;
hp->n_outbuf = 0;
hp->tty = NULL;
if (hp->irq_requested)
/* Saved for use outside of spin_lock. */
irq = hp->irq;
hp->irq_requested = 0;
if (hp->ops->notifier_del)
hp->ops->notifier_del(hp, hp->data);
spin_unlock_irqrestore(&hp->lock, flags);
if (irq)
free_irq(irq, hp);
while(temp_open_count) {
--temp_open_count;
kref_put(&hp->kref, destroy_hvc_struct);
@ -575,7 +530,7 @@ static u32 timeout = MIN_TIMEOUT;
#define HVC_POLL_READ 0x00000001
#define HVC_POLL_WRITE 0x00000002
static int hvc_poll(struct hvc_struct *hp)
int hvc_poll(struct hvc_struct *hp)
{
struct tty_struct *tty;
int i, n, poll_mask = 0;
@ -602,10 +557,10 @@ static int hvc_poll(struct hvc_struct *hp)
if (test_bit(TTY_THROTTLED, &tty->flags))
goto throttled;
/* If we aren't interrupt driven and aren't throttled, we always
/* If we aren't notifier driven and aren't throttled, we always
* request a reschedule
*/
if (hp->irq == 0)
if (!hp->irq_requested)
poll_mask |= HVC_POLL_READ;
/* Read data if any */
@ -733,7 +688,7 @@ static const struct tty_operations hvc_ops = {
.chars_in_buffer = hvc_chars_in_buffer,
};
struct hvc_struct __devinit *hvc_alloc(uint32_t vtermno, int irq,
struct hvc_struct __devinit *hvc_alloc(uint32_t vtermno, int data,
struct hv_ops *ops, int outbuf_size)
{
struct hvc_struct *hp;
@ -754,7 +709,7 @@ struct hvc_struct __devinit *hvc_alloc(uint32_t vtermno, int irq,
memset(hp, 0x00, sizeof(*hp));
hp->vtermno = vtermno;
hp->irq = irq;
hp->data = data;
hp->ops = ops;
hp->outbuf_size = outbuf_size;
hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];