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Commit 611e097d authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Rusty Russell
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hvc_console: rework setup to replace irq functions with callbacks 



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: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 066f4d82

drivers/char/Kconfig

+5 −0
Original line number Diff line number Diff line
@@ -578,11 +578,14 @@ config HVC_DRIVER 
	  It will automatically be selected if one of the back-end console drivers

	  is selected.



config HVC_IRQ

	bool



config HVC_CONSOLE

	bool "pSeries Hypervisor Virtual Console support"

	depends on PPC_PSERIES

	select HVC_DRIVER

	select HVC_IRQ

	help

	  pSeries machines when partitioned support a hypervisor virtual

	  console. This driver allows each pSeries partition to have a console
@@ -593,6 +596,7 @@ config HVC_ISERIES 
	depends on PPC_ISERIES

	default y

	select HVC_DRIVER

	select HVC_IRQ

	help

	  iSeries machines support a hypervisor virtual console.
@@ -614,6 +618,7 @@ config HVC_XEN 
	bool "Xen Hypervisor Console support"

	depends on XEN

	select HVC_DRIVER

	select HVC_IRQ

	default y

	help

	  Xen virtual console device driver

drivers/char/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ obj-$(CONFIG_HVC_ISERIES) += hvc_iseries.o 
obj-$(CONFIG_HVC_RTAS)		+= hvc_rtas.o

obj-$(CONFIG_HVC_BEAT)		+= hvc_beat.o

obj-$(CONFIG_HVC_DRIVER)	+= hvc_console.o

obj-$(CONFIG_HVC_IRQ)		+= hvc_irq.o

obj-$(CONFIG_HVC_XEN)		+= hvc_xen.o

obj-$(CONFIG_VIRTIO_CONSOLE)	+= virtio_console.o

obj-$(CONFIG_RAW_DRIVER)	+= raw.o

drivers/char/hvc_console.c

+18 −63
Original line number Diff line number Diff line
@@ -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))];

drivers/char/hvc_console.h

+31 −4
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ 


#ifndef HVC_CONSOLE_H

#define HVC_CONSOLE_H

#include <linux/kref.h>



/*

 * This is the max number of console adapters that can/will be found as
@@ -42,24 +43,50 @@ 
 */

#define HVC_ALLOC_TTY_ADAPTERS	8



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 data;

	struct list_head next;

	struct kref kref; /* ref count & hvc_struct lifetime */

};



/* implemented by a low level driver */

struct hv_ops {

	int (*get_chars)(uint32_t vtermno, char *buf, int count);

	int (*put_chars)(uint32_t vtermno, const char *buf, int count);

};



struct hvc_struct;

	/* Callbacks for notification. Called in open and close */

	int (*notifier_add)(struct hvc_struct *hp, int irq);

	void (*notifier_del)(struct hvc_struct *hp, int irq);

};



/* Register a vterm and a slot index for use as a console (console_init) */

extern int hvc_instantiate(uint32_t vtermno, int index, struct hv_ops *ops);



/* register a vterm for hvc tty operation (module_init or hotplug add) */

extern struct hvc_struct * __devinit hvc_alloc(uint32_t vtermno, int irq,

extern struct hvc_struct * __devinit hvc_alloc(uint32_t vtermno, int data,

				struct hv_ops *ops, int outbuf_size);

/* remove a vterm from hvc tty operation (modele_exit or hotplug remove) */

/* remove a vterm from hvc tty operation (module_exit or hotplug remove) */

extern int __devexit hvc_remove(struct hvc_struct *hp);



/* data available */

int hvc_poll(struct hvc_struct *hp);

void hvc_kick(void);



/* default notifier for irq based notification */

extern int notifier_add_irq(struct hvc_struct *hp, int data);

extern void notifier_del_irq(struct hvc_struct *hp, int data);





#if defined(CONFIG_XMON) && defined(CONFIG_SMP)

#include <asm/xmon.h>

drivers/char/hvc_irq.c

0 → 100644
+44 −0
Original line number Diff line number Diff line 
/*

 * Copyright IBM Corp. 2001,2008

 *

 * This file contains the IRQ specific code for hvc_console

 *

 */



#include <linux/interrupt.h>



#include "hvc_console.h"



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;

}



/*

 * For IRQ based systems these callbacks can be used

 */

int notifier_add_irq(struct hvc_struct *hp, int irq)

{

	int rc;



	if (!irq) {

		hp->irq_requested = 0;

		return 0;

	}

	rc = request_irq(irq, hvc_handle_interrupt, IRQF_DISABLED,

			   "hvc_console", hp);

	if (!rc)

		hp->irq_requested = 1;

	return rc;

}



void notifier_del_irq(struct hvc_struct *hp, int irq)

{

	if (!irq)

		return;

	free_irq(irq, hp);

	hp->irq_requested = 0;

}