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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __ASM_SPINLOCK_H
#define __ASM_SPINLOCK_H
#include <asm/barrier.h>
#include <asm/ldcw.h>
#include <asm/processor.h>
#include <asm/spinlock_types.h>
static inline int arch_spin_is_locked(arch_spinlock_t *x)
{
volatile unsigned int *a = __ldcw_align(x);
return READ_ONCE(*a) == 0;
}
static inline void arch_spin_lock(arch_spinlock_t *x)
{
volatile unsigned int *a;
a = __ldcw_align(x);
while (__ldcw(a) == 0)
while (*a == 0)
continue;
}
static inline void arch_spin_unlock(arch_spinlock_t *x)
{
volatile unsigned int *a;
a = __ldcw_align(x);
/* Release with ordered store. */
__asm__ __volatile__("stw,ma %0,0(%1)" : : "r"(1), "r"(a) : "memory");
}
static inline int arch_spin_trylock(arch_spinlock_t *x)
{
volatile unsigned int *a;
a = __ldcw_align(x);
return __ldcw(a) != 0;
}
/*
* Read-write spinlocks, allowing multiple readers but only one writer.
* Unfair locking as Writers could be starved indefinitely by Reader(s)
*
* The spinlock itself is contained in @counter and access to it is
* serialized with @lock_mutex.
*/
/* 1 - lock taken successfully */
static inline int arch_read_trylock(arch_rwlock_t *rw)
{
int ret = 0;
unsigned long flags;
local_irq_save(flags);
arch_spin_lock(&(rw->lock_mutex));
/*
* zero means writer holds the lock exclusively, deny Reader.
* Otherwise grant lock to first/subseq reader
*/
if (rw->counter > 0) {
rw->counter--;
ret = 1;
}
arch_spin_unlock(&(rw->lock_mutex));
local_irq_restore(flags);
return ret;
}
/* 1 - lock taken successfully */
static inline int arch_write_trylock(arch_rwlock_t *rw)
{
int ret = 0;
unsigned long flags;
local_irq_save(flags);
arch_spin_lock(&(rw->lock_mutex));
/*
* If reader(s) hold lock (lock < __ARCH_RW_LOCK_UNLOCKED__),
* deny writer. Otherwise if unlocked grant to writer
* Hence the claim that Linux rwlocks are unfair to writers.
* (can be starved for an indefinite time by readers).
*/
if (rw->counter == __ARCH_RW_LOCK_UNLOCKED__) {
rw->counter = 0;
ret = 1;
}
arch_spin_unlock(&(rw->lock_mutex));
local_irq_restore(flags);
return ret;
}
static inline void arch_read_lock(arch_rwlock_t *rw)
{
while (!arch_read_trylock(rw))
cpu_relax();
}
static inline void arch_write_lock(arch_rwlock_t *rw)
{
while (!arch_write_trylock(rw))
cpu_relax();
}
static inline void arch_read_unlock(arch_rwlock_t *rw)
{
unsigned long flags;
local_irq_save(flags);
arch_spin_lock(&(rw->lock_mutex));
rw->counter++;
arch_spin_unlock(&(rw->lock_mutex));
local_irq_restore(flags);
}
static inline void arch_write_unlock(arch_rwlock_t *rw)
{
unsigned long flags;
local_irq_save(flags);
arch_spin_lock(&(rw->lock_mutex));
rw->counter = __ARCH_RW_LOCK_UNLOCKED__;
arch_spin_unlock(&(rw->lock_mutex));
local_irq_restore(flags);
}
#endif /* __ASM_SPINLOCK_H */
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