forked from Minki/linux
419123f900
It does not make sense to try to relinquish the time slice with diag 0x9c to a CPU in a state that does not allow to schedule the CPU. The scenario where this can happen is a CPU waiting in udelay/mdelay while holding a spin-lock. Add a CIF bit to tag a CPU in enabled wait and use it to detect that the yield of a CPU will not be successful and skip the diagnose call. Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
292 lines
6.3 KiB
C
292 lines
6.3 KiB
C
/*
|
|
* 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 = -1;
|
|
|
|
static int __init spin_retry_init(void)
|
|
{
|
|
if (spin_retry < 0)
|
|
spin_retry = MACHINE_HAS_CAD ? 10 : 1000;
|
|
return 0;
|
|
}
|
|
early_initcall(spin_retry_init);
|
|
|
|
/**
|
|
* 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);
|
|
|
|
static inline void _raw_compare_and_delay(unsigned int *lock, unsigned int old)
|
|
{
|
|
asm(".insn rsy,0xeb0000000022,%0,0,%1" : : "d" (old), "Q" (*lock));
|
|
}
|
|
|
|
static inline int cpu_is_preempted(int cpu)
|
|
{
|
|
if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
|
|
return 0;
|
|
if (smp_vcpu_scheduled(cpu))
|
|
return 0;
|
|
return 1;
|
|
}
|
|
|
|
void arch_spin_lock_wait(arch_spinlock_t *lp)
|
|
{
|
|
unsigned int cpu = SPINLOCK_LOCKVAL;
|
|
unsigned int owner;
|
|
int count, first_diag;
|
|
|
|
first_diag = 1;
|
|
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;
|
|
}
|
|
/* First iteration: check if the lock owner is running. */
|
|
if (first_diag && cpu_is_preempted(~owner)) {
|
|
smp_yield_cpu(~owner);
|
|
first_diag = 0;
|
|
continue;
|
|
}
|
|
/* Loop for a while on the lock value. */
|
|
count = spin_retry;
|
|
do {
|
|
if (MACHINE_HAS_CAD)
|
|
_raw_compare_and_delay(&lp->lock, owner);
|
|
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 unconditionally. For LPAR rely on the
|
|
* sense running status.
|
|
*/
|
|
if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
|
|
smp_yield_cpu(~owner);
|
|
first_diag = 0;
|
|
}
|
|
}
|
|
}
|
|
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, first_diag;
|
|
|
|
local_irq_restore(flags);
|
|
first_diag = 1;
|
|
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 (first_diag && cpu_is_preempted(~owner)) {
|
|
smp_yield_cpu(~owner);
|
|
first_diag = 0;
|
|
continue;
|
|
}
|
|
/* Loop for a while on the lock value. */
|
|
count = spin_retry;
|
|
do {
|
|
if (MACHINE_HAS_CAD)
|
|
_raw_compare_and_delay(&lp->lock, owner);
|
|
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 unconditionally. For LPAR rely on the
|
|
* sense running status.
|
|
*/
|
|
if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
|
|
smp_yield_cpu(~owner);
|
|
first_diag = 0;
|
|
}
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(arch_spin_lock_wait_flags);
|
|
|
|
int arch_spin_trylock_retry(arch_spinlock_t *lp)
|
|
{
|
|
unsigned int cpu = SPINLOCK_LOCKVAL;
|
|
unsigned int owner;
|
|
int count;
|
|
|
|
for (count = spin_retry; count > 0; count--) {
|
|
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 1;
|
|
} else if (MACHINE_HAS_CAD)
|
|
_raw_compare_and_delay(&lp->lock, owner);
|
|
}
|
|
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;
|
|
|
|
#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
|
|
__RAW_LOCK(&rw->lock, -1, __RAW_OP_ADD);
|
|
#endif
|
|
owner = 0;
|
|
while (1) {
|
|
if (count-- <= 0) {
|
|
if (owner && cpu_is_preempted(~owner))
|
|
smp_yield_cpu(~owner);
|
|
count = spin_retry;
|
|
}
|
|
old = ACCESS_ONCE(rw->lock);
|
|
owner = ACCESS_ONCE(rw->owner);
|
|
if ((int) old < 0) {
|
|
if (MACHINE_HAS_CAD)
|
|
_raw_compare_and_delay(&rw->lock, old);
|
|
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) {
|
|
if (MACHINE_HAS_CAD)
|
|
_raw_compare_and_delay(&rw->lock, old);
|
|
continue;
|
|
}
|
|
if (_raw_compare_and_swap(&rw->lock, old, old + 1))
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(_raw_read_trylock_retry);
|
|
|
|
#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
|
|
|
|
void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev)
|
|
{
|
|
unsigned int owner, old;
|
|
int count = spin_retry;
|
|
|
|
owner = 0;
|
|
while (1) {
|
|
if (count-- <= 0) {
|
|
if (owner && cpu_is_preempted(~owner))
|
|
smp_yield_cpu(~owner);
|
|
count = spin_retry;
|
|
}
|
|
old = ACCESS_ONCE(rw->lock);
|
|
owner = ACCESS_ONCE(rw->owner);
|
|
smp_mb();
|
|
if ((int) old >= 0) {
|
|
prev = __RAW_LOCK(&rw->lock, 0x80000000, __RAW_OP_OR);
|
|
old = prev;
|
|
}
|
|
if ((old & 0x7fffffff) == 0 && (int) prev >= 0)
|
|
break;
|
|
if (MACHINE_HAS_CAD)
|
|
_raw_compare_and_delay(&rw->lock, old);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(_raw_write_lock_wait);
|
|
|
|
#else /* CONFIG_HAVE_MARCH_Z196_FEATURES */
|
|
|
|
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 && cpu_is_preempted(~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_mb();
|
|
if ((old & 0x7fffffff) == 0 && (int) prev >= 0)
|
|
break;
|
|
if (MACHINE_HAS_CAD)
|
|
_raw_compare_and_delay(&rw->lock, old);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(_raw_write_lock_wait);
|
|
|
|
#endif /* CONFIG_HAVE_MARCH_Z196_FEATURES */
|
|
|
|
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) {
|
|
if (MACHINE_HAS_CAD)
|
|
_raw_compare_and_delay(&rw->lock, 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 && !cpu_is_preempted(~cpu))
|
|
return;
|
|
smp_yield_cpu(~cpu);
|
|
}
|
|
EXPORT_SYMBOL(arch_lock_relax);
|