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/*
* Out of line spinlock code.
*
* Copyright IBM Corp. 2004, 2006
* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
*/
#include <linux/types.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <asm/io.h>
int spin_retry = 1000;
/**
* spin_retry= parameter
*/
static int __init spin_retry_setup(char *str)
{
spin_retry = simple_strtoul(str, &str, 0);
return 1;
}
__setup("spin_retry=", spin_retry_setup);
void arch_spin_lock_wait(arch_spinlock_t *lp)
{
unsigned int cpu = SPINLOCK_LOCKVAL;
unsigned int owner;
int count;
while (1) {
owner = ACCESS_ONCE(lp->lock);
/* Try to get the lock if it is free. */
if (!owner) {
if (_raw_compare_and_swap(&lp->lock, 0, cpu))
return;
continue;
}
/* Check if the lock owner is running. */
if (!smp_vcpu_scheduled(~owner)) {
smp_yield_cpu(~owner);
continue;
}
/* Loop for a while on the lock value. */
count = spin_retry;
do {
owner = ACCESS_ONCE(lp->lock);
} while (owner && count-- > 0);
if (!owner)
continue;
/*
* For multiple layers of hypervisors, e.g. z/VM + LPAR
* yield the CPU if the lock is still unavailable.
*/
if (!MACHINE_IS_LPAR)
smp_yield_cpu(~owner);
}
}
EXPORT_SYMBOL(arch_spin_lock_wait);
void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
{
unsigned int cpu = SPINLOCK_LOCKVAL;
unsigned int owner;
int count;
local_irq_restore(flags);
while (1) {
owner = ACCESS_ONCE(lp->lock);
/* Try to get the lock if it is free. */
if (!owner) {
local_irq_disable();
if (_raw_compare_and_swap(&lp->lock, 0, cpu))
return;
local_irq_restore(flags);
}
/* Check if the lock owner is running. */
if (!smp_vcpu_scheduled(~owner)) {
smp_yield_cpu(~owner);
continue;
}
/* Loop for a while on the lock value. */
count = spin_retry;
do {
owner = ACCESS_ONCE(lp->lock);
} while (owner && count-- > 0);
if (!owner)
continue;
/*
* For multiple layers of hypervisors, e.g. z/VM + LPAR
* yield the CPU if the lock is still unavailable.
*/
if (!MACHINE_IS_LPAR)
smp_yield_cpu(~owner);
}
}
EXPORT_SYMBOL(arch_spin_lock_wait_flags);
int arch_spin_trylock_retry(arch_spinlock_t *lp)
{
int count;
for (count = spin_retry; count > 0; count--)
if (arch_spin_trylock_once(lp))
return 1;
return 0;
}
EXPORT_SYMBOL(arch_spin_trylock_retry);
void _raw_read_lock_wait(arch_rwlock_t *rw)
{
unsigned int owner, old;
int count = spin_retry;
owner = 0;
while (1) {
if (count-- <= 0) {
if (owner && !smp_vcpu_scheduled(~owner))
smp_yield_cpu(~owner);
count = spin_retry;
}
old = ACCESS_ONCE(rw->lock);
owner = ACCESS_ONCE(rw->owner);
if ((int) old < 0)
continue;
if (_raw_compare_and_swap(&rw->lock, old, old + 1))
return;
}
}
EXPORT_SYMBOL(_raw_read_lock_wait);
int _raw_read_trylock_retry(arch_rwlock_t *rw)
{
unsigned int old;
int count = spin_retry;
while (count-- > 0) {
old = ACCESS_ONCE(rw->lock);
if ((int) old < 0)
continue;
if (_raw_compare_and_swap(&rw->lock, old, old + 1))
return 1;
}
return 0;
}
EXPORT_SYMBOL(_raw_read_trylock_retry);
void _raw_write_lock_wait(arch_rwlock_t *rw)
{
unsigned int owner, old, prev;
int count = spin_retry;
prev = 0x80000000;
owner = 0;
while (1) {
if (count-- <= 0) {
if (owner && !smp_vcpu_scheduled(~owner))
smp_yield_cpu(~owner);
count = spin_retry;
}
old = ACCESS_ONCE(rw->lock);
owner = ACCESS_ONCE(rw->owner);
if ((int) old >= 0 &&
_raw_compare_and_swap(&rw->lock, old, old | 0x80000000))
prev = old;
else
smp_rmb();
if ((old & 0x7fffffff) == 0 && (int) prev >= 0)
break;
}
}
EXPORT_SYMBOL(_raw_write_lock_wait);
int _raw_write_trylock_retry(arch_rwlock_t *rw)
{
unsigned int old;
int count = spin_retry;
while (count-- > 0) {
old = ACCESS_ONCE(rw->lock);
if (old)
continue;
if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000))
return 1;
}
return 0;
}
EXPORT_SYMBOL(_raw_write_trylock_retry);
void arch_lock_relax(unsigned int cpu)
{
if (!cpu)
return;
if (MACHINE_IS_LPAR && smp_vcpu_scheduled(~cpu))
return;
smp_yield_cpu(~cpu);
}
EXPORT_SYMBOL(arch_lock_relax);
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