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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2006-09-30 23:27:43 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-01 00:39:21 -0700
commitef6edc9746dc2bfdacf44eefd5f881179971c478 (patch)
treee8670e918a852978b2e93e189936f327be072284 /kernel/spinlock.c
parente3e5fc91d9828a9b94a3992de47d47d2d2e34ec6 (diff)
[PATCH] Directed yield: cpu_relax variants for spinlocks and rw-locks
On systems running with virtual cpus there is optimization potential in regard to spinlocks and rw-locks. If the virtual cpu that has taken a lock is known to a cpu that wants to acquire the same lock it is beneficial to yield the timeslice of the virtual cpu in favour of the cpu that has the lock (directed yield). With CONFIG_PREEMPT="n" this can be implemented by the architecture without common code changes. Powerpc already does this. With CONFIG_PREEMPT="y" the lock loops are coded with _raw_spin_trylock, _raw_read_trylock and _raw_write_trylock in kernel/spinlock.c. If the lock could not be taken cpu_relax is called. A directed yield is not possible because cpu_relax doesn't know anything about the lock. To be able to yield the lock in favour of the current lock holder variants of cpu_relax for spinlocks and rw-locks are needed. The new _raw_spin_relax, _raw_read_relax and _raw_write_relax primitives differ from cpu_relax insofar that they have an argument: a pointer to the lock structure. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Paul Mackerras <paulus@samba.org> Cc: Haavard Skinnemoen <hskinnemoen@atmel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel/spinlock.c')
-rw-r--r--kernel/spinlock.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/spinlock.c b/kernel/spinlock.c
index d48143eafbfd..476c3741511b 100644
--- a/kernel/spinlock.c
+++ b/kernel/spinlock.c
@@ -215,7 +215,7 @@ void __lockfunc _##op##_lock(locktype##_t *lock) \
if (!(lock)->break_lock) \
(lock)->break_lock = 1; \
while (!op##_can_lock(lock) && (lock)->break_lock) \
- cpu_relax(); \
+ _raw_##op##_relax(&lock->raw_lock); \
} \
(lock)->break_lock = 0; \
} \
@@ -237,7 +237,7 @@ unsigned long __lockfunc _##op##_lock_irqsave(locktype##_t *lock) \
if (!(lock)->break_lock) \
(lock)->break_lock = 1; \
while (!op##_can_lock(lock) && (lock)->break_lock) \
- cpu_relax(); \
+ _raw_##op##_relax(&lock->raw_lock); \
} \
(lock)->break_lock = 0; \
return flags; \

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/*
 *	w83697ug/uf WDT driver
 *
 *	(c) Copyright 2008 Flemming Fransen <ff@nrvissing.net>
 *		reused original code to support w83697ug/uf.
 *
 *	Based on w83627hf_wdt.c which is based on advantechwdt.c
 *	which is based on wdt.c.
 *	Original copyright messages:
 *
 *	(c) Copyright 2007 Vlad Drukker <vlad@storewiz.com>
 *		added support for W83627THF.
 *
 *	(c) Copyright 2003 Pádraig Brady <P@draigBrady.com>
 *
 *	(c) Copyright 2000-2001 Marek Michalkiewicz <marekm@linux.org.pl>
 *
 *	(c) Copyright 1996 Alan Cox <alan@redhat.com>, All Rights Reserved.
 *				http://www.redhat.com
 *
 *	This program is free software; you can redistribute it and/or
 *	modify it under the terms of the GNU General Public License
 *	as published by the Free Software Foundation; either version
 *	2 of the License, or (at your option) any later version.
 *
 *	Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
 *	warranty for any of this software. This material is provided
 *	"AS-IS" and at no charge.
 *
 *	(c) Copyright 1995    Alan Cox <alan@redhat.com>
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/ioport.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/io.h>
#include <linux/uaccess.h>

#include <asm/system.h>

#define WATCHDOG_NAME "w83697ug/uf WDT"
#define PFX WATCHDOG_NAME ": "
#define WATCHDOG_TIMEOUT 60		/* 60 sec default timeout */

static unsigned long wdt_is_open;
static char expect_close;
static DEFINE_SPINLOCK(io_lock);

static int wdt_io = 0x2e;
module_param(wdt_io, int, 0);
MODULE_PARM_DESC(wdt_io, "w83697ug/uf WDT io port (default 0x2e)");

static int timeout = WATCHDOG_TIMEOUT;	/* in seconds */
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
	"Watchdog timeout in seconds. 1<= timeout <=255 (default="
				__MODULE_STRING(WATCHDOG_TIMEOUT) ")");

static int nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, int, 0);
MODULE_PARM_DESC(nowayout,
	"Watchdog cannot be stopped once started (default="
				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

/*
 *	Kernel methods.
 */

#define WDT_EFER (wdt_io+0)   /* Extended Function Enable Registers */
#define WDT_EFIR (wdt_io+0)   /* Extended Function Index Register
							(same as EFER) */
#define WDT_EFDR (WDT_EFIR+1) /* Extended Function Data Register */

static int w83697ug_select_wd_register(void)
{
	unsigned char c;
	unsigned char version;

	outb_p(0x87, WDT_EFER); /* Enter extended function mode */
	outb_p(0x87, WDT_EFER); /* Again according to manual */

	outb(0x20, WDT_EFER); 	/* check chip version	*/
	version = inb(WDT_EFDR);

	if (version == 0x68) {	/* W83697UG 		*/
		printk(KERN_INFO PFX "Watchdog chip version 0x%02x = "
			"W83697UG/UF found at 0x%04x\n", version, wdt_io);

		outb_p(0x2b, WDT_EFER);
		c = inb_p(WDT_EFDR);    /* select WDT0 */
		c &= ~0x04;
		outb_p(0x2b, WDT_EFER);
		outb_p(c, WDT_EFDR);	/* set pin118 to WDT0 */

	} else {
		printk(KERN_ERR PFX "No W83697UG/UF could be found\n");
		return -ENODEV;
	}

	outb_p(0x07, WDT_EFER); /* point to logical device number reg */
	outb_p(0x08, WDT_EFDR); /* select logical device 8 (GPIO2) */
	outb_p(0x30, WDT_EFER); /* select CR30 */
	c = inb_p(WDT_EFDR);
	outb_p(c || 0x01, WDT_EFDR); /* set bit 0 to activate GPIO2 */

	return 0;
}

static void w83697ug_unselect_wd_register(void)
{
	outb_p(0xAA, WDT_EFER); /* Leave extended function mode */
}

static int w83697ug_init(void)
{
	int ret;
	unsigned char t;

	ret = w83697ug_select_wd_register();
	if (ret != 0)
		return ret;

	outb_p(0xF6, WDT_EFER); /* Select CRF6 */
	t = inb_p(WDT_EFDR);    /* read CRF6 */
	if (t != 0) {
		printk(KERN_INFO PFX "Watchdog already running."
			" Resetting timeout to %d sec\n", timeout);
		outb_p(timeout, WDT_EFDR);    /* Write back to CRF6 */
	}
	outb_p(0xF5, WDT_EFER); /* Select CRF5 */
	t = inb_p(WDT_EFDR);    /* read CRF5 */
	t &= ~0x0C;             /* set second mode &
					disable keyboard turning off watchdog */
	outb_p(t, WDT_EFDR);    /* Write back to CRF5 */

	w83697ug_unselect_wd_register();
	return 0;
}

static void wdt_ctrl(int timeout)
{
	spin_lock(&io_lock);

	if (w83697ug_select_wd_register() < 0) {
		spin_unlock(&io_lock);
		return;
	}

	outb_p(0xF4, WDT_EFER);    /* Select CRF4 */
	outb_p(timeout, WDT_EFDR); /* Write Timeout counter to CRF4 */

	w83697ug_unselect_wd_register();

	spin_unlock(&io_lock);
}

static int wdt_ping(void)
{
	wdt_ctrl(timeout);
	return 0;
}

static int wdt_disable(void)
{
	wdt_ctrl(0);
	return 0;
}

static int wdt_set_heartbeat(int t)
{
	if (t < 1 || t > 255)
		return -EINVAL;

	timeout = t;
	return 0;
}

static ssize_t wdt_write(struct file *file, const char __user *buf,
						size_t count, loff_t *ppos)
{
	if (count) {
		if (!nowayout) {
			size_t i;

			expect_close = 0;

			for (i = 0; i != count; i++) {
				char c;
				if (get_user(c, buf + i))
					return -EFAULT;
				if (c == 'V')
					expect_close = 42;
			}
		}
		wdt_ping();
	}
	return count;
}

static long wdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
	void __user *argp = (void __user *)arg;
	int __user *p = argp;
	int new_timeout;
	static const struct watchdog_info ident = {
		.options =		WDIOF_KEEPALIVEPING |
					WDIOF_SETTIMEOUT |
					WDIOF_MAGICCLOSE,
		.firmware_version =	1,
		.identity =		"W83697UG WDT",
	};

	switch (cmd) {
	case WDIOC_GETSUPPORT:
		if (copy_to_user(argp, &ident, sizeof(ident)))
			return -EFAULT;
		break;

	case WDIOC_GETSTATUS:
	case WDIOC_GETBOOTSTATUS:
		return put_user(0, p);

	case WDIOC_SETOPTIONS:
	{
		int options, retval = -EINVAL;

		if (get_user(options, p))
			return -EFAULT;

		if (options & WDIOS_DISABLECARD) {
			wdt_disable();
			retval = 0;
		}

		if (options & WDIOS_ENABLECARD) {
			wdt_ping();
			retval = 0;
		}

		return retval;
	}

	case WDIOC_KEEPALIVE:
		wdt_ping();
		break;

	case WDIOC_SETTIMEOUT:
		if (get_user(new_timeout, p))
			return -EFAULT;
		if (wdt_set_heartbeat(new_timeout))
			return -EINVAL;
		wdt_ping();
		/* Fall */

	case WDIOC_GETTIMEOUT:
		return put_user(timeout, p);

	default:
		return -ENOTTY;
	}
	return 0;
}

static int wdt_open(struct inode *inode, struct file *file)
{
	if (test_and_set_bit(0, &wdt_is_open))
		return -EBUSY;
	/*
	 *	Activate
	 */

	wdt_ping();
	return nonseekable_open(inode, file);
}

static int wdt_close(struct inode *inode, struct file *file)
{
	if (expect_close == 42)
		wdt_disable();
	else {
		printk(KERN_CRIT PFX
			"Unexpected close, not stopping watchdog!\n");
		wdt_ping();
	}
	expect_close = 0;
	clear_bit(0, &wdt_is_open);
	return 0;
}

/*
 *	Notifier for system down
 */

static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
	void *unused)
{
	if (code == SYS_DOWN || code == SYS_HALT)
		wdt_disable();	/* Turn the WDT off */

	return NOTIFY_DONE;
}

/*
 *	Kernel Interfaces
 */

static const struct file_operations wdt_fops = {
	.owner		= THIS_MODULE,
	.llseek		= no_llseek,
	.write		= wdt_write,
	.unlocked_ioctl	= wdt_ioctl,
	.open		= wdt_open,
	.release	= wdt_close,
};

static struct miscdevice wdt_miscdev = {
	.minor = WATCHDOG_MINOR,
	.name = "watchdog",
	.fops = &wdt_fops,
};

/*
 *	The WDT needs to learn about soft shutdowns in order to
 *	turn the timebomb registers off.
 */

static struct notifier_block wdt_notifier = {
	.notifier_call = wdt_notify_sys,
};

static int __init wdt_init(void)
{
	int ret;

	printk(KERN_INFO "WDT driver for the Winbond(TM) W83697UG/UF Super I/O chip initialising.\n");

	if (wdt_set_heartbeat(timeout)) {
		wdt_set_heartbeat(WATCHDOG_TIMEOUT);
		printk(KERN_INFO PFX
			"timeout value must be 1<=timeout<=255, using %d\n",
			WATCHDOG_TIMEOUT);
	}

	if (!request_region(wdt_io, 1, WATCHDOG_NAME)) {
		printk(KERN_ERR PFX "I/O address 0x%04x already in use\n",
			wdt_io);
		ret = -EIO;
		goto out;
	}

	ret = w83697ug_init();
	if (ret != 0)
		goto unreg_regions;

	ret = register_reboot_notifier(&wdt_notifier);
	if (ret != 0) {
		printk(KERN_ERR PFX
			"cannot register reboot notifier (err=%d)\n", ret);
		goto unreg_regions;
	}

	ret = misc_register(&wdt_miscdev);
	if (ret != 0) {
		printk(KERN_ERR PFX
			"cannot register miscdev on minor=%d (err=%d)\n",
			WATCHDOG_MINOR, ret);
		goto unreg_reboot;
	}

	printk(KERN_INFO PFX "initialized. timeout=%d sec (nowayout=%d)\n",
		timeout, nowayout);

out:
	return ret;
unreg_reboot:
	unregister_reboot_notifier(&wdt_notifier);
unreg_regions:
	release_region(wdt_io, 1);
	goto out;
}

static void __exit wdt_exit(void)
{
	misc_deregister(&wdt_miscdev);
	unregister_reboot_notifier(&wdt_notifier);
	release_region(wdt_io, 1);
}

module_init(wdt_init);
module_exit(wdt_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Flemming Frandsen <ff@nrvissing.net>");
MODULE_DESCRIPTION("w83697ug/uf WDT driver");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);

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