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/*
* Copyright (c) 2000 Silicon Graphics, Inc. All Rights Reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of version 2 of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it would be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*
* Further, this software is distributed without any warranty that it is
* free of the rightful claim of any third person regarding infringement
* or the like. Any license provided herein, whether implied or
* otherwise, applies only to this software file. Patent licenses, if
* any, provided herein do not apply to combinations of this program with
* other software, or any other product whatsoever.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write the Free Software Foundation, Inc., 59
* Temple Place - Suite 330, Boston MA 02111-1307, USA.
*
* Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
* Mountain View, CA 94043, or:
*
* http://www.sgi.com
*
* For further information regarding this notice, see:
*
* http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
*/
#include <linux/time.h>
#include <linux/sched.h>
#include <asm/system.h>
#include <linux/interrupt.h>
#include <asm/current.h>
#include <linux/module.h> /* for EXPORT_SYMBOL */
#include <linux/xfs_support/support.h>
spinlock_t Atomic_spin = SPIN_LOCK_UNLOCKED;
#if USE_RW_WAIT_QUEUE_SPINLOCK
# define wq_write_lock write_lock
#else
# define wq_write_lock spin_lock
#endif
/*
* We don't seem to need lock_type (only one supported), name, or
* sequence. But, XFS will pass it so let's leave them here for now.
*/
/* ARGSUSED */
void
mrlock_init(mrlock_t *mrp, int lock_type, char *name, long sequence)
{
mrp->mr_count = 0;
mrp->mr_reads_waiting = 0;
mrp->mr_writes_waiting = 0;
init_waitqueue_head(&mrp->mr_readerq);
init_waitqueue_head(&mrp->mr_writerq);
mrp->mr_lock = SPIN_LOCK_UNLOCKED;
}
/*
* Macros to lock/unlock the mrlock_t.
*/
#define MRLOCK_INT(m, s) spin_lock_irqsave(&(m)->mr_lock, s);
#define MRUNLOCK_INT(m, s) spin_unlock_irqrestore(&(m)->mr_lock, s);
#define MRLOCK(m) spin_lock_irq(&(m)->mr_lock);
#define MRUNLOCK(m) spin_unlock_irq(&(m)->mr_lock);
/*
* lock_wait should never be called in an interrupt thread.
*
* mrlocks can sleep (i.e. call schedule) and so they can't ever
* be called from an interrupt thread.
*
* threads that wake-up should also never be invoked from interrupt threads.
*
* But, waitqueue_lock is locked from interrupt threads - and we are
* called with interrupts disabled, so it is all OK.
*/
/* ARGSUSED */
void
lock_wait(wait_queue_head_t *q, spinlock_t *lock, int rw)
{
DECLARE_WAITQUEUE( wait, current );
set_current_state(TASK_UNINTERRUPTIBLE);
wq_write_lock(&q->lock);
if (rw) {
__add_wait_queue_tail(q, &wait);
} else {
__add_wait_queue(q, &wait);
}
wq_write_unlock(&q->lock);
spin_unlock_irq(lock); /* Interrupts reenabled */
schedule();
set_current_state(TASK_RUNNING);
wq_write_lock_irq(&q->lock);
__remove_wait_queue(q, &wait);
wq_write_unlock(&q->lock);
spin_lock(lock);
/* return with interrupts off and lock held */
}
/* ARGSUSED */
void
mrfree(mrlock_t *mrp)
{
}
/* ARGSUSED */
void
mrlock(mrlock_t *mrp, int type, int flags)
{
if (type == MR_ACCESS)
mraccess(mrp);
else
mrupdate(mrp);
}
/* ARGSUSED */
void
mraccessf(mrlock_t *mrp, int flags)
{
MRLOCK(mrp);
if(mrp->mr_writes_waiting > 0) {
mrp->mr_reads_waiting++;
lock_wait(&mrp->mr_readerq, &mrp->mr_lock, 0);
mrp->mr_reads_waiting--;
}
while (mrp->mr_count < 0) {
mrp->mr_reads_waiting++;
lock_wait(&mrp->mr_readerq, &mrp->mr_lock, 0);
mrp->mr_reads_waiting--;
}
mrp->mr_count++;
MRUNLOCK(mrp);
}
/* ARGSUSED */
void
mrupdatef(mrlock_t *mrp, int flags)
{
MRLOCK(mrp);
while(mrp->mr_count) {
mrp->mr_writes_waiting++;
lock_wait(&mrp->mr_writerq, &mrp->mr_lock, 1);
mrp->mr_writes_waiting--;
}
mrp->mr_count = -1; /* writer on it */
MRUNLOCK(mrp);
}
int
mrtryaccess(mrlock_t *mrp)
{
long s;
MRLOCK_INT(mrp, s);
/*
* If anyone is waiting for update access or the lock is held for update
* fail the request.
*/
if(mrp->mr_writes_waiting > 0 || mrp->mr_count < 0) {
MRUNLOCK_INT(mrp, s);
return 0;
}
mrp->mr_count++;
MRUNLOCK_INT(mrp, s);
return 1;
}
int
mrtrypromote(mrlock_t *mrp)
{
long s;
MRLOCK_INT(mrp, s);
if(mrp->mr_count == 1) { /* We are the only thread with the lock */
mrp->mr_count = -1; /* writer on it */
MRUNLOCK_INT(mrp, s);
return 1;
}
MRUNLOCK_INT(mrp, s);
return 0;
}
int
mrtryupdate(mrlock_t *mrp)
{
long s;
MRLOCK_INT(mrp, s);
if(mrp->mr_count) {
MRUNLOCK_INT(mrp, s);
return 0;
}
mrp->mr_count = -1; /* writer on it */
MRUNLOCK_INT(mrp, s);
return 1;
}
static __inline__ void mrwake(mrlock_t *mrp)
{
/*
* First, if the count is now 0, we need to wake-up anyone waiting.
*/
if (!mrp->mr_count) {
if (mrp->mr_writes_waiting) { /* Wake-up first writer waiting */
wake_up(&mrp->mr_writerq);
} else if (mrp->mr_reads_waiting) { /* Wakeup any readers waiting */
wake_up(&mrp->mr_readerq);
}
}
}
void
mraccunlock(mrlock_t *mrp)
{
long s;
MRLOCK_INT(mrp, s);
mrp->mr_count--;
mrwake(mrp);
MRUNLOCK_INT(mrp, s);
}
void
mrunlock(mrlock_t *mrp)
{
long s;
MRLOCK_INT(mrp, s);
if (mrp->mr_count < 0) {
mrp->mr_count = 0;
} else {
mrp->mr_count--;
}
mrwake(mrp);
MRUNLOCK_INT(mrp, s);
}
int
ismrlocked(mrlock_t *mrp, int type) /* No need to lock since info can change */
{
if (type == MR_ACCESS)
return (mrp->mr_count > 0); /* Read lock */
else if (type == MR_UPDATE)
return (mrp->mr_count < 0); /* Write lock */
else if (type == (MR_UPDATE | MR_ACCESS))
return (mrp->mr_count); /* Any type of lock held */
else /* Any waiters */
return (mrp->mr_reads_waiting | mrp->mr_writes_waiting);
}
/*
* Demote from update to access. We better be the only thread with the
* lock in update mode so it should be easy to set to 1.
* Wake-up any readers waiting.
*/
void
mrdemote(mrlock_t *mrp)
{
MRLOCK(mrp);
mrp->mr_count = 1;
if (mrp->mr_reads_waiting) { /* Wakeup all readers waiting */
wake_up(&mrp->mr_readerq);
}
MRUNLOCK(mrp);
}
int
mrislocked_access(mrlock_t *mrp)
{
return(mrp->mr_count > 0);
}
int
mrislocked_update(mrlock_t *mrp)
{
return(mrp->mr_count < 0);
}
EXPORT_SYMBOL(mraccessf);
EXPORT_SYMBOL(mrupdatef);
EXPORT_SYMBOL(mrlock);
EXPORT_SYMBOL(mrunlock);
EXPORT_SYMBOL(mraccunlock);
EXPORT_SYMBOL(mrtryupdate);
EXPORT_SYMBOL(mrtryaccess);
EXPORT_SYMBOL(mrtrypromote);
EXPORT_SYMBOL(mrdemote);
EXPORT_SYMBOL(ismrlocked);
EXPORT_SYMBOL(mrlock_init);
EXPORT_SYMBOL(mrfree);
EXPORT_SYMBOL(Atomic_spin);
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